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§ 1910.272
29 CFR Ch. XVII (7–1–07 Edition)
8. Standard for Pneumatic Conveying Systems
for Handling Feed, Flour, Grain and Other Agricultural Dusts, NFPA 66; National Fire Protection Association, Batterymarch Park,
Quincy, Massachusetts 02269.
9. Guide for Explosion Venting, NFPA 68; National
Fire
Protection
Association,
Batterymarch Park, Quincy, Massachusetts
02269.
10. Standard on Explosion Prevention Systems, NFPA 69; National Fire Protection Association, Batterymarch Park, Quincy, Massachusetts 02269.
11. Safety-Operations Plans; U.S. Department of Agriculture, Washington, DC 20250.
12. Inplant Fire Prevention Control Programs;
Mill Mutual Fire Prevention Mutual Fire
Prevention Bureau, 1 Pierce Place, Suite 1260
West, Itasca, Illinois 60143–1269.
13. Guidelines for Terminal Elevators; Mill
Mutual Fire Prevention Bureau, 1 Pierce
Place, Suite 1260 West, Itasca, Illinois 60143–
1269.
14. Standards for Preventing the Horizontal
and Vertical Spread of Fires in Grain Handling
Properties; Mill Mutual Fire Mutual Fire Prevention Bureau, 1 Pierce Place, Suite 1260
West, Itasca, Illinois 60143–1269.
15. Belt Conveyors for Bulk Materials, Part I
and Part II, Data Sheet 570, Revision A; National Safety Council, 425 North Michigan
Avenue, Chicago, Illinois 60611.
16. Suggestions for Precautions and Safety
Practices in Welding and Cutting; Mill Mutual
Fire Prevention Bureau, 1 Pierce Place,
Suite 1260 West, Itasca, Illinois 60143–1269.
17. Food Bins and Tanks, Data Sheet 524;
National Safety Council, 425 North Michigan
Avenue, Chicago, Illinois 60611.
18. Pneumatic Dust Control in Grain Elevators; National Academy of Sciences, Washington, DC. (Available from National Technical Information Service, Springfield, Virginia 22151.)
19. Dust Control Analysis and Layout Procedures for Grain Storage and Processing Plants;
Mill Mutual Fire Prevention Bureau, 1
Pierce Place, Suite 1260 West, Itasca, Illinois
60143–1269.
20. Standard for the Installation of Blower
and Exhaust Systems for Dust, Stock and Vapor
Removal, NFPA 91; National Fire Protection
Association, Batterymarch Park, Quincy,
Massachusetts 02269.
21. Standards for the Installation of Direct
Heat Grain Driers in Grain and Milling Properties; Mill Mutual Fire Prevention Bureau, 1
Pierce Place, Suite 1260 West, Itasca, Illinois
60143–1269.
22. Guidelines for Lubrication and Bearing
Maintenance; Mill Mutual Fire Prevention
Bureau, 1 Pierce Place, Suite 1260 West,
Itasca, Illinois 60143–1269.
23. Organized Maintenance in Grain and Milling Properties; Mill Mutual Fire Prevention
Bureau, 1 Pierce Place, Suite 1260 West,
Itasca, Illinois 60143–1269.
24. Safe and Efficient Elevator Legs for Grain
and Milling Properties; Mill Mutual Fire Prevention Bureau, 1 Pierce Place, Suite 1260
West, Itasca, Illinois 60143–1269.
25. Explosion Venting and Supression of
Bucket Elevators; National Grain and Feed
Association, P.O. Box 28328, Washington, DC
20005.
26. Lightning Protection Code, NFPA 78; National
Fire
Protection
Association,
Batterymarch Park, Quincy, Massachusetts
02269.
27. Occupational Safety in Grain Elevators,
DHHS (NIOSH) Publication No. 83–126); National Institute for Occupational Safety and
Health, Morgantown, West Virginia 26505.
28. Retrofitting and Constructing Grain Elevators; National Grain and Feed Association,
P.O. Box 28328, Washington, DC 20005.
29. Grain Industry Safety and Health Center—Training Series (Preventing grain dust
explosions, operations maintenance safety,
transportation safety, occupational safety
and health); Grain Elevator and Processing
Society, P.O. Box 15026, Commerce Station,
Minneapolis, Minnesota 55415–0026.
30. Suggestions for Organized Maintenance;
The Mill Mutuals Loss Control Department,
1 Pierce Place, Suite 1260 West, Itasca, Illinois 60143–1269.
31. Safety—The First Step to Success; The
Mill Mutual Loss Control Department, 1
Pierce Place, Suite 1260 West, Itasca, Illinois
60143–1269.
32. Emergency Plan Notebook; Schoeff, Robert W. and James L. Balding, Kansas State
University, Cooperative Extension Service,
Extension Grain Science and Industry,
Shellenberger Hall, Manhattan, Kansas 66506.
[52 FR 49625, Dec. 31, 1987, as amended at 53
FR 17696, May 18, 1988; 54 FR 24334, June 7,
1989; 55 FR 25094, June 20, 1990; 61 FR 9242,
Mar. 7, 1996; 61 FR 9584, Mar. 8, 1996; 67 FR
67965, Nov. 7, 2002]
Subpart S—Electrical
AUTHORITY: Secs. 4, 6, 8, Occupational Safety and Health Act of 1970 (29 U.S.C. 653, 655,
657; Secretary of Labor’s Order No. 8–76 (41
FR 25059) or 1–90 (55 FR 9033), as applicable;
29 CFR part 1911.
EFFECTIVE DATE NOTE: At 72 FR 7190, Feb.
14, 2007, the authority citation for Subpart S
was revised, effective Aug. 13, 2007. For the
convenience of the user, the added and revised text is set forth as follows:
AUTHORITY: Secs. 4, 6, 8, Occupational Safety and Health Act of 1970 (29 U.S.C. 653, 655,
657); Secretary of Labor’s Order No. 8–76 (41
FR 25059), 1–90 (55 FR 9033), or 5–2002 (67 F.R.
65008), as applicable; 29 CFR Part 1911.
SOURCE: 46 FR 4056, Jan. 16, 1981, unless
otherwise noted.
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Occupational Safety and Health Admin., Labor
GENERAL
§ 1910.301 Introduction.
This subpart addresses electrical
safety requirements that are necessary
for the practical safeguarding of employees in their workplaces and is divided into four major divisions as follows:
(a) Design safety standards for electrical systems. These regulations are
contained in §§ 1910.302 through 1910.330.
Sections 1910.302 through 1910.308 contain design safety standards for electric utilization systems. Included in
this category are all electric equipment and installations used to provide
electric power and light for employee
workplaces. Sections 1910.309 through
1910.330 are reserved for possible future
design safety standards for other electrical systems.
(b) Safety-related work practices. These
regulations will be contained in
§§ 1910.331 through 1910.360.
(c) Safety-related maintenance requirements. These regulations will be contained in §§ 1910.361 through 1910.380.
(d) Safety requirements for special
equipment. These regulations will be
contained in §§ 1910.381 through 1910.398.
(e) Definitions. Definitions applicable
to each division are contained in
§ 1910.399.
[46 FR 4056, Jan. 16, 1982; 46 FR 40185, Aug. 7,
1981]
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DESIGN SAFETY STANDARDS FOR
ELECTRICAL SYSTEMS
§ 1910.302 Electric utilization systems.
Sections 1910.302 through 1910.308 contain design safety standards for electric utilization systems.
(a) Scope—(1) Covered. The provisions
of §§ 1910.302 through 1910.308 of this
subpart cover electrical installations
and utilization equipment installed or
used within or on buildings, structures,
and other premises including:
(i) Yards,
(ii) Carnivals,
(iii) Parking and other lots,
(iv) Mobile homes,
(v) Recreational vehicles,
(vi) Industrial substations,
(vii) Conductors that connect the installations to a supply of electricity,
and
§ 1910.302
(viii) Other outside conductors on the
premises.
(2) Not covered. The provisions of
§§ 1910.302 through 1910.308 of this subpart do not cover:
(i) Installations in ships, watercraft,
railway rolling stock, aircraft, or automotive vehicles other than mobile
homes and recreational vehicles.
(ii) Installations underground in
mines.
(iii) Installations of railways for generation, transformation, transmission,
or distribution of power used exclusively for operation of rolling stock or
installations used exclusively for signaling and communication purposes.
(iv) Installations of communication
equipment under the exclusive control
of communication utilities, located
outdoors or in building spaces used exclusively for such installations.
(v) Installations under the exclusive
control of electric utilities for the purpose of communication or metering; or
for the generation, control, transformation, transmission, and distribution of electric energy located in buildings used exclusively by utilities for
such purposes or located outdoors on
property owned or leased by the utility
or on public highways, streets, roads,
etc., or outdoors by established rights
on private property.
(b) Extent of application. (1) The requirements contained in the sections
listed below shall apply to all electrical installations and utilization
equipment, regardless of when they
were designed or installed.
Sections:
1910.303(b) ..................
1910.303(c) ...................
1910.303(d) ..................
1910.303(e) ..................
1910.303(f) ...................
1910.303(g)(2) ..............
1910.304(e)(l)(i) ............
1910.304(e)(l)(iv) ..........
1910.304(e)(l)(v) ...........
1910.304(f)(l)(ii) ............
1910.304(f)(l)(iii) and
1910.304(f)(l)(iv).
1910.304(f)(l)(v) ............
1910.304(f)(3) ...............
1910.304(f)(4) ...............
1910.304(f)(5)(iv)(a)
through
1910.304(f)(5)(iv)(d).
Examination, installation, and use
of equipment.
Splices.
Arcing parts.
Marking.
Identification
of
disconnecting
means.
Guarding of live parts.
Protection of conductors and
equipment.
Location in or on premises.
Arcing or suddenly moving parts.
2-Wire DC systems to be grounded:
AC Systems to be grounded.
AC Systems 50 to 1000 volts not
required to be grounded.
Grounding connections.
Grounding path.
Fixed equipment required to be
grounded.
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§ 1910.302
1910.304(f)(5)(v) ...........
1910.304(f)(5)(vi) ..........
1910.304(f)(6)(i) ............
1910.305(g)(l)(i) and
1910.305(g)(1)(ii).
1910.305(g)(l)(iii) ..........
1910.305(g)(2)(ii) ..........
1910.305(g)(2)(iii) .........
1910.307 .......................
29 CFR Ch. XVII (7–1–07 Edition)
Grounding of equipment connected
by cord and plug.
Grounding of nonelectrical equipment.
Methods of grounding fixed equipment.
Flexible cords and cables, uses.
Flexible cords and cables prohibited.
Flexible cords and cables, splices.
Pull at joints and terminals of flexible cords and cables.
Hazardous (classified) locations.
(2) Every electric utilization system
and all utilization equipment installed
after March 15, 1972, and every major
replacement, modification, repair, or
rehabilitation, after March 15, 1972, of
any part of any electric utilization system or utilization equipment installed
before March 15, 1972, shall comply
with the provisions of §§ 1910.302
through 1910.308.
NOTE: ‘‘Major replacements, modifications,
repairs, or rehabilitations’’ include work
similar to that involved when a new building
or facility is built, a new wing is added, or an
entire floor is renovated.
(3) The following provisions apply to
electric utilization systems and utilization equipment installed after April
16, 1981:
§ 1910.303(h)(4) (i) and
(ii).
§ 1910.304(e)(1)(vi)(b) ..
§ 1910.304(e)(1)(vi)(c) ..
§ 1910.304(f)(7)(ii) ........
§ 1910.305(j)(6)(ii)(b) ....
§ 1910.306(c)(2) ............
§ 1910.306(i) .................
§ 1910.306(j)(5) .............
§ 1910.308(a)(1)(ii) .......
§ 1910.308(c)(2) ............
§ 1910.308(d) ................
Entrance and access to workspace
(over 600 volts).
Circuit breakers operated vertically.
Circuit breakers used as switches.
Grounding of systems of 1000
volts or more supplying portable
or mobile equipment.
Switching series capacitors over
600 volts.
Warning signs for elevators and
escalators.
Electrically controlled irrigation machines.
Ground-fault circuit interrupters for
fountains.
Physical protection of conductors
over 600 volts.
Marking of Class 2 and Class 3
power supplies.
Fire protective signaling circuits.
[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7,
1981]
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EFFECTIVE DATE NOTE: At 72 FR 7190, Feb.
14, 2007, § 1910.302 was revised, effective Aug.
13, 2007. For the convenience of the user, the
revised text is set forth as follows:
§ 1910.302 Electric utilization systems.
Sections 1910.302 through 1910.308 contain
design safety standards for electric utilization systems.
(a) Scope—(1) Covered. The provisions of
§§ 1910.302 through 1910.308 cover electrical in-
stallations and utilization equipment installed or used within or on buildings, structures, and other premises, including:
(i) Yards;
(ii) Carnivals;
(iii) Parking and other lots;
(iv) Mobile homes;
(v) Recreational vehicles;
(vi) Industrial substations;
(vii) Conductors that connect the installations to a supply of electricity; and
(viii) Other outside conductors on the
premises.
(2) Not covered. The provisions of §§ 1910.302
through 1910.308 do not cover:
(i) Installations in ships, watercraft, railway rolling stock, aircraft, or automotive
vehicles other than mobile homes and recreational vehicles;
(ii) Installations underground in mines;
(iii) Installations of railways for generation, transformation, transmission, or distribution of power used exclusively for operation of rolling stock or installations used
exclusively for signaling and communication
purposes;
(iv) Installations of communication equipment under the exclusive control of communication utilities, located outdoors or in
building spaces used exclusively for such installations; or
(v) Installations under the exclusive control of electric utilities for the purpose of
communication or metering; or for the generation, control, transformation, transmission, and distribution of electric energy
located in buildings used exclusively by utilities for such purposes or located outdoors
on property owned or leased by the utility or
on public highways, streets, roads, etc., or
outdoors by established rights on private
property.
(b) Extent of application—(1) Requirements
applicable to all installations. The following
requirements apply to all electrical installations and utilization equipment, regardless
of when they were designed or installed:
§ 1910.303(b)—Examination, installation, and
use of equipment
§ 1910.303(c)(3)—Electrical
connections—
Splices
§ 1910.303(d)—Arcing parts
§ 1910.303(e)—Marking
§ 1910.303(f), except (f)(4) and (f)(5)—Disconnecting means and circuits
§ 1910.303(g)(2)—600 volts or less—Guarding of
live parts
§ 1910.304(a)(3)—Use of grounding terminals
and devices
§ 1910.304(f)(1)(i), (f)(1)(iv), and (f)(1)(v)—Overcurrent protection—600 volts, nominal, or
less
§ 1910.304(g)(1)(ii), (g)(1)(iii), (g)(1)(iv), and
(g)(1)(v)—Grounding—Systems
to
be
grounded
§ 1910.304(g)(4)—Grounding—Grounding connections
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Occupational Safety and Health Admin., Labor
§ 1910.304(g)(5)—Grounding—Grounding path
§ 1910.304(g)(6)(iv)(A) through (g)(6)(iv)(D),
and (g)(6)(vi)—Grounding—Supports, enclosures, and equipment to be grounded
§ 1910.304(g)(7)—Grounding—Nonelectrical
equipment
§ 1910.304(g)(8)(i)—Grounding—Methods
of
grounding fixed equipment
§ 1910.305(g)(1)—Flexible cords and cables—
Use of flexible cords and cables
§ 1910.305(g)(2)(ii)
and
(g)(2)(iii)—Flexible
cords and cables—Identification, splices,
and terminations
§ 1910.307, except as specified in § 1910.307(b)—
Hazardous (classified) locations
(2) Requirements applicable to installations
made after March 15, 1972. Every electrical installation and all utilization equipment installed or overhauled after March 15, 1972,
shall comply with the provisions of §§ 1910.302
through 1910.308, except as noted in paragraphs (b)(3) and (b)(4) of this section.
(3) Requirements applicable only to installations made after April 16, 1981. The following
requirements apply only to electrical installations and utilization equipment installed
after April 16, 1981:
§ 1910.303(h)(4)—Over 600 volts, nominal—Entrance and access to work space
§ 1910.304(f)(1)(vii) and (f)(1)(viii)—Overcurrent protection—600 volts, nominal, or less
§ 1910.304(g)(9)(i)—Grounding—Grounding
of
systems and circuits of 1000 volts and over
(high voltage)
§ 1910.305(j)(6)(ii)(D)—Equipment for general
use—Capacitors
§ 1910.306(c)(9)—Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and
stairway chair lifts—Interconnection between multicar controllers
§ 1910.306(i)—Electrically driven or controlled
irrigation machines
§ 1910.306(j)(5)—Swimming pools, fountains,
and similar installations—Fountains
§ 1910.308(a)(1)(ii)—Systems over 600 volts,
nominal—Aboveground wiring methods
§ 1910.308(c)(2)—Class 1, Class 2, and Class 3
remote control, signaling, and power-limited circuits—Marking
§ 1910.308(d)—Fire alarm systems
(4) Requirements applicable only to installations made after August 13, 2007. The following
requirements apply only to electrical installations and utilization equipment installed
after August 13, 2007:
§ 1910.303(f)(4)—Disconnecting means and circuits—Capable of accepting a lock
§ 1910.303(f)(5)—Disconnecting means and circuits—Marking for series combination ratings
§ 1910.303(g)(1)(iv) and (g)(1)(vii)—600 Volts,
nominal, or less—Space about electric
equipment
§ 1910.303(h)(5)(vi)—Over 600 volts, nominal—
Working space and guarding
§ 1910.303
§ 1910.304(b)(1)—Branch circuits—Identification of multiwire branch circuits
§ 1910.304(b)(3)(i)—Branch
circuits—Groundfault circuit interrupter protection for personnel
§ 1910.304(f)(2)(i)(A), (f)(2)(i)(B) (but not the
introductory text to § 1910.304(f)(2)(i)), and
(f)(2)(iv)(A)—Overcurrent
protection—
Feeders and branch circuits over 600 volts,
nominal
§ 1910.305(c)(3)(ii)—Switches—Connection
of
switches
§ 1910.305(c)(5)—Switches—Grounding
§ 1910.306(a)(1)(ii)—Electric signs and outline
lighting—Disconnecting means
§ 1910.306(c)(4)—Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and
stairway chair lifts—Operation
§ 1910.306(c)(5)—Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and
stairway chair lifts—Location
§ 1910.306(c)(6)—Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and
stairway chair lifts—Identification and
signs
§ 1910.306(c)(7)—Elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and
stairway
chair
lifts—Single-car
and
multicar installations
§ 1910.306(j)(1)(iii)—Swimming pools, fountains, and similar installations—Receptacles
§ 1910.306(k)—Carnivals, circuses, fairs, and
similar events
§ 1910.308(a)(5)(v) and (a)(5)(vi)(B)—Systems
over 600 volts, nominal—Interrupting and
isolating devices
§ 1910.308(a)(7)(vi)—Systems over 600 volts,
nominal—Tunnel installations
§ 1910.308(b)(3)—Emergency power systems—
Signs
§ 1910.308(c)(3)—Class 1, Class 2, and Class 3
remote control, signaling, and power-limited circuits—Separation from conductors
of other circuits
§ 1910.308(f)—Solar photovoltaic systems
(c) Applicability of requirements for disconnecting means. The requirement in
§ 1910.147(c)(2)(iii) that energy isolating devices be capable of accepting a lockout device whenever replacement or major repair,
renovation or modification of a machine or
equipment is performed, and whenever new
machines or equipment are installed after
January 2, 1990, applies in addition to any requirements in § 1910.303 through § 1910.308
that disconnecting means be capable of being
locked in the open position under certain
conditions.
§ 1910.303
General requirements.
(a) Approval. The conductors and
equipment required or permitted by
this subpart shall be acceptable only if
approved.
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§ 1910.303
29 CFR Ch. XVII (7–1–07 Edition)
(b) Examination, installation, and use
of equipment—(1) Examination. Electrical equipment shall be free from recognized hazards that are likely to
cause death or serious physical harm
to employees. Safety of equipment
shall be determined using the following
considerations:
(i) Suitability for installation and
use in conformity with the provisions
of this subpart. Suitability of equipment for an identified purpose may be
evidenced by listing or labeling for
that identified purpose.
(ii) Mechanical strength and durability, including, for parts designed to
enclose and protect other equipment,
the adequacy of the protection thus
provided.
(iii) Electrical insulation.
(iv) Heating effects under conditions
of use.
(v) Arcing effects.
(vi) Classification by type, size, voltage, current capacity, specific use.
(vii) Other factors which contribute
to the practical safeguarding of employees using or likely to come in contact with the equipment.
(2) Installation and use. Listed or labeled equipment shall be used or installed in accordance with any instructions included in the listing or labeling.
(c) Splices. Conductors shall be
spliced or joined with splicing devices
suitable for the use or by brazing, welding, or soldering with a fusible metal
or alloy. Soldered splices shall first be
so spliced or joined as to be mechanically and electrically secure without
solder and then soldered. All splices
and joints and the free ends of conductors shall be covered with an insulation
equivalent to that of the conductors or
with an insulating device suitable for
the purpose.
(d) Arcing parts. Parts of electric
equipment which in ordinary operation
produce arcs, sparks, flames, or molten
metal shall be enclosed or separated
and isolated from all combustible material.
(e) Marking. Electrical equipment
may not be used unless the manufacturer’s name, trademark, or other descriptive marking by which the organization responsible for the product may
be identified is placed on the equip-
ment. Other markings shall be provided giving voltage, current, wattage,
or other ratings as necessary. The
marking shall be of sufficient durability to withstand the environment involved.
(f) Identification of disconnecting
means and circuits. Each disconnecting
means required by this subpart for motors and appliances shall be legibly
marked to indicate its purpose, unless
located and arranged so the purpose is
evident. Each service, feeder, and
branch circuit, at its disconnecting
means or overcurrent device, shall be
legibly marked to indicate its purpose,
unless located and arranged so the purpose is evident. These markings shall
be of sufficient durability to withstand
the environment involved.
(g) 600 Volts, nominal, or less—(1)
Working space about electric equipment.
Sufficient access and working space
shall be provided and maintained about
all electric equipment to permit ready
and safe operation and maintenance of
such equipment.
(i) Working clearances. Except as required or permitted elsewhere in this
subpart, the dimension of the working
space in the direction of access to live
parts operating at 600 volts or less and
likely to require examination, adjustment, servicing, or maintenance while
alive may not be less than indicated in
Table S–1. In addition to the dimensions shown in Table S–1, workspace
may not be less than 30 inches wide in
front of the electric equipment. Distances shall be measured from the live
parts if they are exposed, or from the
enclosure front or opening if the live
parts are enclosed. Concrete, brick, or
tile walls are considered to be grounded. Working space is not required in
back of assemblies such as dead-front
switchboards or motor control centers
where there are no renewable or adjustable parts such as fuses or switches on
the back and where all connections are
accessible from locations other than
the back.
TABLE S–1—WORKING CLEARANCES
Nominal voltage to ground
Minimum clear distance
for condition2 (ft)
(a)
0–150 .........................................
13
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(b)
13
(c)
3
Occupational Safety and Health Admin., Labor
TABLE S–1—WORKING CLEARANCES—
Continued
Nominal voltage to ground
Minimum clear distance
for condition2 (ft)
(a)
151–600 .....................................
13
(b)
31⁄2
(c)
4
1 Minimum
clear distances may be 2 feet 6 inches for installations built prior to April 16, 1981.
2 Conditions (a), (b), and (c), are as follows: (a) Exposed
live parts on one side and no live or grounded parts on the
other side of the working space, or exposed live parts on both
sides effectively guarded by suitable wood or other insulating
material. Insulated wire or insulated busbars operating at not
over 300 volts are not considered live parts. (b) Exposed live
parts on one side and grounded parts on the other side. (c)
Exposed live parts on both sides of the workspace [not guarded as provided in Condition (a)] with the operator between.
(ii) Clear spaces. Working space required by this subpart may not be used
for storage. When normally enclosed
live parts are exposed for inspection or
servicing, the working space, if in a
passageway or general open space,
shall be suitably guarded.
(iii) Access and entrance to working
space. At least one entrance of sufficient area shall be provided to give access to the working space about electric equipment.
(iv) Front working space. Where there
are live parts normally exposed on the
front of switchboards or motor control
centers, the working space in front of
such equipment may not be less than 3
feet.
(v) Illumination. Illumination shall be
provided for all working spaces about
service equipment, switchboards, panelboards, and motor control centers installed indoors.
(vi) Headroom. The minimum headroom of working spaces about service
equipment, switchboards, panel-boards,
or motor control centers shall be 6 feet
3 inches.
rfrederick on PROD1PC67 with CFR
NOTE: As used in this section a motor control center is an assembly of one or more enclosed sections having a common power bus
and principally containing motor control
units.
(2) Guarding of live parts. (i) Except as
required or permitted elsewhere in this
subpart, live parts of electric equipment operating at 50 volts or more
shall be guarded against accidental
contact by approved cabinets or other
forms of approved enclosures, or by any
of the following means:
§ 1910.303
(A) By location in a room, vault, or
similar enclosure that is accessible
only to qualified persons.
(B) By suitable permanent, substantial partitions or screens so arranged
that only qualified persons will have
access to the space within reach of the
live parts. Any openings in such partitions or screens shall be so sized and
located that persons are not likely to
come into accidental contact with the
live parts or to bring conducting objects into contact with them.
(C) By location on a suitable balcony,
gallery, or platform so elevated and arranged as to exclude unqualified persons.
(D) By elevation of 8 feet or more
above the floor or other working surface.
(ii) In locations where electric equipment would be exposed to physical
damage, enclosures or guards shall be
so arranged and of such strength as to
prevent such damage.
(iii) Entrances to rooms and other
guarded locations containing exposed
live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter.
(h) Over 600 volts, nominal—(1) General. Conductors and equipment used on
circuits exceeding 600 volts, nominal,
shall comply with all applicable provisions of paragraphs (a) through (g) of
this section and with the following provisions which supplement or modify
those requirements. The provisions of
paragraphs (h)(2), (h)(3), and (h)(4) of
this section do not apply to equipment
on the supply side of the service conductors.
(2) Enclosure for electrical installations.
Electrical installations in a vault,
room, closet or in an area surrounded
by a wall, screen, or fence, access to
which is controlled by lock and key or
other approved means, are considered
to be accessible to qualified persons
only. A wall, screen, or fence less than
8 feet in height is not considered to
prevent access unless it has other features that provide a degree of isolation
equivalent to an 8 foot fence. The entrances to all buildings, rooms, or enclosures containing exposed live parts
or exposed conductors operating at
over 600 volts, nominal, shall be kept
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§ 1910.303
29 CFR Ch. XVII (7–1–07 Edition)
locked or shall be under the observation of a qualified person at all times.
(i) Installations accessible to qualified
persons only. Electrical installations
having exposed live parts shall be accessible to qualified persons only and
shall comply with the applicable provisions of paragraph (h)(3) of this section.
(ii) Installations accessible to unqualified persons. Electrical installations
that are open to unqualified persons
shall be made with metal-enclosed
equipment or shall be enclosed in a
vault or in an area, access to which is
controlled by a lock. If metal-enclosed
equipment is installed so that the bottom of the enclosure is less than 8 feet
above the floor, the door or cover shall
be
kept
locked.
Metal-enclosed
switchgear, unit substations, transformers, pull boxes, connection boxes,
and other similar associated equipment
shall be marked with appropriate caution signs. If equipment is exposed to
physical damage from vehicular traffic,
suitable guards shall be provided to
prevent such damage. Ventilating or
similar openings in metal-enclosed
equipment shall be designed so that
foreign objects inserted through these
openings will be deflected from energized parts.
(3) Workspace about equipment. Sufficient space shall be provided and maintained about electric equipment to permit ready and safe operation and maintenance of such equipment. Where energized parts are exposed, the minimum clear workspace may not be less
than 6 feet 6 inches high (measured
vertically from the floor or platform),
or less than 3 feet wide (measured parallel to the equipment). The depth
shall be as required in Table S–2. The
workspace shall be adequate to permit
at least a 90-degree opening of doors or
hinged panels.
(i) Working space. The minimum clear
working space in front of electric
equipment such as switchboards, control panels, switches, circuit breakers,
motor controllers, relays, and similar
equipment may not be less than specified in Table S–2 unless otherwise specified in this subpart. Distances shall be
measured from the live parts if they
are exposed, or from the enclosure
front or opening if the live parts are
enclosed. However, working space is
not required in back of equipment such
as deadfront switchboards or control
assemblies where there are no renewable or adjustable parts (such as fuses
or switches) on the back and where all
connections are accessible from locations other than the back. Where rear
access is required to work on de-energized parts on the back of enclosed
equipment, a minimum working space
of 30 inches horizontally shall be provided.
TABLE S–2—MINIMUM DEPTH OF CLEAR WORKING SPACE IN FRONT OF ELECTRIC EQUIPMENT
Conditions 2 (ft)
Nominal voltage to ground
(a)
601 to 2,500 ..............................
2,501 to 9,000 ...........................
9,001 to 25,000 .........................
25,001 to 75kV 1 ........................
Above 75kV 1 .............................
(b)
3
4
5
6
8
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6
9
10
12
1 Minimum depth of clear working space in front of electric
equipment with a nominal voltage to ground above 25,000
volts may be the same as for 25,000 volts under Conditions
(a), (b), and (c) for installations built prior to April 16, 1981.
2 Conditions (a), (b), and (c) are as follows: (a) Exposed live
parts on one side and no live or grounded parts on the other
side of the working space, or exposed live parts on both sides
effectively guarded by suitable wood or other insulating materials. Insulated wire or insulated busbars operating at not over
300 volts are not considered live parts. (b) Exposed live parts
on one side and grounded parts on the other side. Concrete,
brick, or tile walls will be considered as grounded surfaces. (c)
Exposed live parts on both sides of the workspace not guarded as provided in Condition (a) with the operator between.
(ii) Illumination. Adequate illumination shall be provided for all working
spaces about electric equipment. The
lighting outlets shall be so arranged
that persons changing lamps or making
repairs on the lighting system will not
be endangered by live parts or other
equipment. The points of control shall
be so located that persons are not likely to come in contact with any live
part or moving part of the equipment
while turning on the lights.
(iii) Elevation of unguarded live parts.
Unguarded live parts above working
space shall be maintained at elevations
not less than specified in Table S–3.
TABLE S–3—ELEVATION OF UNGUARDED
ENERGIZED PARTS ABOVE WORKING SPACE
Nominal voltage between phases
601 to 7,500 .................
7,501 to 35,000 ............
Minimum elevation
*8 feet 6 inches.
9 feet.
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6
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10
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Occupational Safety and Health Admin., Labor
TABLE S–3—ELEVATION OF UNGUARDED ENERGIZED PARTS ABOVE WORKING SPACE—Continued
Nominal voltage between phases
Minimum elevation
Over 35kV ....................
9 feet + 0.37 inches per kV above
35kV.
*Note. Minimum elevation may be 8 feet 0 inches for installations built prior to April 16, 1981 if the nominal voltage between phases is in the range of 601–6600 volts.
(4) Entrance and access to workspace.
(See § 1910.302(b)(3).)
(i) At least one entrance not less
than 24 inches wide and 6 feet 6 inches
high shall be provided to give access to
the working space about electric equipment. On switchboard and control panels exceeding 48 inches in width, there
shall be one entrance at each end of
such board where practicable. Where
bare energized parts at any voltage or
insulated energized parts above 600
volts are located adjacent to such entrance, they shall be suitably guarded.
(ii) Permanent ladders or stairways
shall be provided to give safe access to
the working space around electric
equipment installed on platforms, balconies, mezzanine floors, or in attic or
roof rooms or spaces.
[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7,
1981]
EFFECTIVE DATE NOTE: At 72 FR 7191, Feb.
14, 2007, § 1910.303 was revised, effective Aug.
13, 2007. For the convenience of the user, the
revised text is set forth as follows:
rfrederick on PROD1PC67 with CFR
§ 1910.303 General.
(a) Approval. The conductors and equipment required or permitted by this subpart
shall be acceptable only if approved, as defined in § 1910.399.
(b) Examination, installation, and use of
equipment—(1) Examination. Electric equipment shall be free from recognized hazards
that are likely to cause death or serious
physical harm to employees. Safety of equipment shall be determined using the following
considerations:
(i) Suitability for installation and use in
conformity with the provisions of this subpart;
NOTE TO PARAGRAPH (B)(1)(I) OF THIS SECTION: Suitability of equipment for an identified purpose may be evidenced by listing or
labeling for that identified purpose.
(ii) Mechanical strength and durability, including, for parts designed to enclose and
protect other equipment, the adequacy of the
protection thus provided;
§ 1910.303
(iii) Wire-bending and connection space;
(iv) Electrical insulation;
(v) Heating effects under all conditions of
use;
(vi) Arcing effects;
(vii) Classification by type, size, voltage,
current capacity, and specific use; and
(viii) Other factors that contribute to the
practical safeguarding of persons using or
likely to come in contact with the equipment.
(2) Installation and use. Listed or labeled
equipment shall be installed and used in accordance with any instructions included in
the listing or labeling.
(3) Insulation integrity. Completed wiring
installations shall be free from short circuits
and from grounds other than those required
or permitted by this subpart.
(4) Interrupting rating. Equipment intended
to interrupt current at fault levels shall
have an interrupting rating sufficient for the
nominal circuit voltage and the current that
is available at the line terminals of the
equipment. Equipment intended to interrupt
current at other than fault levels shall have
an interrupting rating at nominal circuit
voltage sufficient for the current that must
be interrupted.
(5) Circuit impedance and other characteristics. The overcurrent protective devices, the
total impedance, the component short-circuit current ratings, and other characteristics of the circuit to be protected shall be selected and coordinated to permit the circuit
protective devices used to clear a fault to do
so without the occurrence of extensive damage to the electrical components of the circuit. This fault shall be assumed to be either
between two or more of the circuit conductors, or between any circuit conductor and
the grounding conductor or enclosing metal
raceway.
(6) Deteriorating agents. Unless identified
for use in the operating environment, no
conductors or equipment shall be located in
damp or wet locations; where exposed to
gases, fumes, vapors, liquids, or other agents
that have a deteriorating effect on the conductors or equipment; or where exposed to
excessive temperatures.
(7) Mechanical execution of work. Electric
equipment shall be installed in a neat and
workmanlike manner.
(i) Unused openings in boxes, raceways,
auxiliary gutters, cabinets, equipment cases,
or housings shall be effectively closed to afford protection substantially equivalent to
the wall of the equipment.
(ii) Conductors shall be racked to provide
ready and safe access in underground and
subsurface enclosures that persons enter for
installation and maintenance.
(iii) Internal parts of electrical equipment,
including
busbars,
wiring
terminals,
insulators, and other surfaces, may not be
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§ 1910.303
29 CFR Ch. XVII (7–1–07 Edition)
damaged or contaminated by foreign materials such as paint, plaster, cleaners, abrasives, or corrosive residues.
(iv) There shall be no damaged parts that
may adversely affect safe operation or mechanical strength of the equipment, such as
parts that are broken, bent, cut, or deteriorated by corrosion, chemical action, or overheating.
(8) Mounting and cooling of equipment. (i)
Electric equipment shall be firmly secured
to the surface on which it is mounted.
NOTE TO PARAGRAPH (B)(8)(I) OF THIS SECTION: Wooden plugs driven into holes in ma-
rfrederick on PROD1PC67 with CFR
sonry, concrete, plaster, or similar materials
are not considered secure means of fastening
electric equipment.
(ii) Electric equipment that depends on the
natural circulation of air and convection
principles for cooling of exposed surfaces
shall be installed so that room airflow over
such surfaces is not prevented by walls or by
adjacent installed equipment. For equipment
designed for floor mounting, clearance between top surfaces and adjacent surfaces
shall be provided to dissipate rising warm
air.
(iii) Electric equipment provided with ventilating openings shall be installed so that
walls or other obstructions do not prevent
the free circulation of air through the equipment.
(c) Electrical connections—(1) General. Because of different characteristics of dissimilar metals:
(i) Devices such as pressure terminal or
pressure splicing connectors and soldering
lugs shall be identified for the material of
the conductor and shall be properly installed
and used;
(ii) Conductors of dissimilar metals may
not be intermixed in a terminal or splicing
connector where physical contact occurs between dissimilar conductors (such as copper
and aluminum, copper and copper-clad aluminum, or aluminum and copper-clad aluminum) unless the device is identified for
the purpose and conditions of use; and
(iii) Materials such as solder, fluxes, inhibitors, and compounds, where employed,
shall be suitable for the use and shall be of
a type that will not adversely affect the conductors, installation, or equipment.
(2) Terminals. (i) Connection of conductors
to terminal parts shall ensure a good connection without damaging the conductors and
shall be made by means of pressure connectors (including set-screw type), solder lugs,
or splices to flexible leads. However, No. 10
or smaller conductors may be connected by
means of wire binding screws or studs and
nuts having upturned lugs or equivalent.
(ii) Terminals for more than one conductor
and terminals used to connect aluminum
shall be so identified.
(3) Splices. (i) Conductors shall be spliced or
joined with splicing devices identified for the
use or by brazing, welding, or soldering with
a fusible metal or alloy. Soldered splices
shall first be spliced or joined to be mechanically and electrically secure without solder
and then soldered. All splices and joints and
the free ends of conductors shall be covered
with an insulation equivalent to that of the
conductors or with an insulating device identified for the purpose.
(ii) Wire connectors or splicing means installed on conductors for direct burial shall
be listed for such use.
(d) Arcing parts. Parts of electric equipment that in ordinary operation produce
arcs, sparks, flames, or molten metal shall
be enclosed or separated and isolated from
all combustible material.
(e) Marking—(1) Identification of manufacturer and ratings. Electric equipment may
not be used unless the following markings
have been placed on the equipment:
(i) The manufacturer’s name, trademark,
or other descriptive marking by which the
organization responsible for the product may
be identified; and
(ii) Other markings giving voltage, current, wattage, or other ratings as necessary.
(2) Durability. The marking shall be of sufficient durability to withstand the environment involved.
(f) Disconnecting means and circuits—(1) Motors and appliances. Each disconnecting
means required by this subpart for motors
and appliances shall be legibly marked to indicate its purpose, unless located and arranged so the purpose is evident.
(2) Services, feeders, and branch circuits.
Each service, feeder, and branch circuit, at
its disconnecting means or overcurrent device, shall be legibly marked to indicate its
purpose, unless located and arranged so the
purpose is evident.
(3) Durability of markings. The markings required by paragraphs (f)(1) and (f)(2) of this
section shall be of sufficient durability to
withstand the environment involved.
(4) Capable of accepting a lock. Disconnecting means required by this subpart
shall be capable of being locked in the open
position.
(5) Marking for series combination ratings. (i)
Where circuit breakers or fuses are applied
in compliance with the series combination
ratings marked on the equipment by the
manufacturer, the equipment enclosures
shall be legibly marked in the field to indicate that the equipment has been applied
with a series combination rating.
(ii) The marking required by paragraph
(f)(5)(i) of this section shall be readily visible
and shall state ‘‘Caution—Series Combination System Rated ll Amperes. Identified
Replacement Component Required.’’
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§ 1910.303
(iii) At least one entrance of sufficient
area shall be provided to give access to the
working space about electric equipment.
(iv) For equipment rated 1200 amperes or
more and over 1.83 m (6.0 ft) wide, containing
overcurrent devices, switching devices, or
control devices, there shall be one entrance
not less than 610 mm (24 in.) wide and 1.98 m
(6.5 ft) high at each end of the working space,
except that:
(A) Where the location permits a continuous and unobstructed way of exit travel,
one means of exit is permitted; or
(B) Where the working space required by
paragraph (g)(1)(i) of this section is doubled,
only one entrance to the working space is required; however, the entrance shall be located so that the edge of the entrance nearest the equipment is the minimum clear distance given in Table S–1 away from such
equipment.
(v) Illumination shall be provided for all
working spaces about service equipment,
switchboards, panelboards, and motor control centers installed indoors. Additional
lighting fixtures are not required where the
working space is illuminated by an adjacent
light source. In electric equipment rooms,
the illumination may not be controlled by
automatic means only.
(vi) The minimum headroom of working
spaces about service equipment, switchboards, panelboards, or motor control centers shall be as follows:
(A) For installations built before August
13, 2007, 1.91 m (6.25 ft); and
(B) For installations built on or after August 13, 2007, 1.98 m (6.5 ft), except that where
the electrical equipment exceeds 1.98 m (6.5
ft) in height, the minimum headroom may
not be less than the height of the equipment.
(g) 600 Volts, nominal, or less. This paragraph applies to electric equipment operating at 600 volts, nominal, or less to ground.
(1) Space about electric equipment. Sufficient
access and working space shall be provided
and maintained about all electric equipment
to permit ready and safe operation and maintenance of such equipment.
(i) Working space for equipment likely to
require examination, adjustment, servicing,
or maintenance while energized shall comply
with the following dimensions, except as required or permitted elsewhere in this subpart:
(A) The depth of the working space in the
direction of access to live parts may not be
less than indicated in Table S–1. Distances
shall be measured from the live parts if they
are exposed or from the enclosure front or
opening if they are enclosed;
(B) The width of working space in front of
the electric equipment shall be the width of
the equipment or 762 mm (30 in.), whichever
is greater. In all cases, the working space
shall permit at least a 90-degree opening of
equipment doors or hinged panels; and
(C) The work space shall be clear and extend from the grade, floor, or platform to the
height required by paragraph (g)(1)(vi) of this
section. However, other equipment associated with the electrical installation and located above or below the electric equipment
may extend not more than 153 mm (6 in.) beyond the front of the electric equipment.
(ii) Working space required by this standard may not be used for storage. When normally enclosed live parts are exposed for inspection or servicing, the working space, if
in a passageway or general open space, shall
be suitably guarded.
TABLE S–1—MINIMUM DEPTH OF CLEAR WORKING SPACE AT ELECTRIC EQUIPMENT, 600 V OR LESS
Minimum clear distance for condition 2 3
Nominal voltage to ground
Condition A
m
0–150 ............................................................................
151–600 ........................................................................
Condition B
ft
m
Condition C
ft
m
10.9
13.0
10.9
13.0
10.9
13.0
1.0
3.5
ft
0.9
1.2
3.0
4.0
rfrederick on PROD1PC67 with CFR
Notes to Table S–1:
1. Minimum clear distances may be 0.7 m (2.5 ft) for installations built before April 16, 1981.
2. Conditions A, B, and C are as follows:
Condition A—Exposed live parts on one side and no live or grounded parts on the other side of the working space, or exposed live parts on both sides effectively guarded by suitable wood or other insulating material. Insulated wire or insulated
busbars operating at not over 300 volts are not considered live parts.
Condition B—Exposed live parts on one side and grounded parts on the other side.
Condition C—Exposed live parts on both sides of the work space (not guarded as provided in Condition A) with the operator
between.
3. Working space is not required in back of assemblies such as dead-front switchboards or motor control centers where there
are no renewable or adjustable parts (such as fuses or switches) on the back and where all connections are accessible from locations other than the back. Where rear access is required to work on deenergized parts on the back of enclosed equipment, a
minimum working space of 762 mm (30 in.) horizontally shall be provided.
(vii) Switchboards, panelboards, and distribution boards installed for the control of
light and power circuits, and motor control
centers shall be located in dedicated spaces
and protected from damage.
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§ 1910.303
29 CFR Ch. XVII (7–1–07 Edition)
(A) For indoor installation, the dedicated
space shall comply with the following:
(1) The space equal to the width and depth
of the equipment and extending from the
floor to a height of 1.83 m (6.0 ft) above the
equipment or to the structural ceiling,
whichever is lower, shall be dedicated to the
electrical installation. Unless isolated from
equipment by height or physical enclosures
or covers that will afford adequate mechanical protection from vehicular traffic or accidental contact by unauthorized personnel or
that complies with paragraph (g)(1)(vii)(A)(2)
of this section, piping, ducts, or equipment
foreign to the electrical installation may not
be located in this area;
(2) The space equal to the width and depth
of the equipment shall be kept clear of foreign systems unless protection is provided to
avoid damage from condensation, leaks, or
breaks in such foreign systems. This area
shall extend from the top of the electric
equipment to the structural ceiling;
(3) Sprinkler protection is permitted for
the dedicated space where the piping complies with this section; and
(4) Control equipment that by its very nature or because of other requirements in this
subpart must be adjacent to or within sight
of its operating machinery is permitted in
the dedicated space.
NOTE TO PARAGRAPH (g)(1)(vii)(A) OF THIS
SECTION: A dropped, suspended, or similar
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ceiling that does not add strength to the
building structure is not considered a structural ceiling.
(B) Outdoor electric equipment shall be installed in suitable enclosures and shall be
protected from accidental contact by unauthorized personnel, or by vehicular traffic, or
by accidental spillage or leakage from piping
systems. No architectural appurtenance or
other equipment may be located in the working space required by paragraph (g)(1)(i) of
this section.
(2) Guarding of live parts. (i) Except as elsewhere required or permitted by this standard, live parts of electric equipment operating at 50 volts or more shall be guarded
against accidental contact by use of approved cabinets or other forms of approved
enclosures or by any of the following means:
(A) By location in a room, vault, or similar
enclosure that is accessible only to qualified
persons;
(B) By suitable permanent, substantial
partitions or screens so arranged so that
only qualified persons will have access to the
space within reach of the live parts. Any
openings in such partitions or screens shall
be so sized and located that persons are not
likely to come into accidental contact with
the live parts or to bring conducting objects
into contact with them;
(C) By placement on a suitable balcony,
gallery, or platform so elevated and other-
wise located as to prevent access by unqualified persons; or
(D) By elevation of 2.44 m (8.0 ft) or more
above the floor or other working surface.
(ii) In locations where electric equipment
is likely to be exposed to physical damage,
enclosures or guards shall be so arranged and
of such strength as to prevent such damage.
(iii) Entrances to rooms and other guarded
locations containing exposed live parts shall
be marked with conspicuous warning signs
forbidding unqualified persons to enter.
(h) Over 600 volts, nominal—(1) General. Conductors and equipment used on circuits exceeding 600 volts, nominal, shall comply with
all applicable provisions of the paragraphs
(a) through (g) of this section and with the
following provisions, which supplement or
modify the preceding requirements. However, paragraphs (h)(2), (h)(3), and (h)(4) of
this section do not apply to the equipment
on the supply side of the service point.
(2) Enclosure for electrical installations. (i)
Electrical installations in a vault, room, or
closet or in an area surrounded by a wall,
screen, or fence, access to which is controlled by lock and key or other approved
means, are considered to be accessible to
qualified persons only. The type of enclosure
used in a given case shall be designed and
constructed according to the hazards associated with the installation.
(ii) For installations other than equipment
described in paragraph (h)(2)(v) of this section, a wall, screen, or fence shall be used to
enclose an outdoor electrical installation to
deter access by persons who are not qualified. A fence may not be less than 2.13 m (7.0
ft) in height or a combination of 1.80 m (6.0
ft) or more of fence fabric and a 305-mm (1ft) or more extension utilizing three or more
strands of barbed wire or equivalent.
(iii) The following requirements apply to
indoor installations that are accessible to
other than qualified persons:
(A) The installations shall be made with
metal-enclosed equipment or shall be enclosed in a vault or in an area to which access is controlled by a lock;
(B) Metal-enclosed switchgear, unit substations, transformers, pull boxes, connection boxes, and other similar associated
equipment shall be marked with appropriate
caution signs; and
(C) Openings in ventilated dry-type transformers and similar openings in other equipment shall be designed so that foreign objects inserted through these openings will be
deflected from energized parts.
(iv) Outdoor electrical installations having
exposed live parts shall be accessible to
qualified persons only.
(v) The following requirements apply to
outdoor enclosed equipment accessible to unqualified employees:
(A) Ventilating or similar openings in
equipment shall be so designed that foreign
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Occupational Safety and Health Admin., Labor
objects inserted through these openings will
be deflected from energized parts;
(B) Where exposed to physical damage
from vehicular traffic, suitable guards shall
be provided;
(C) Nonmetallic or metal-enclosed equipment located outdoors and accessible to the
general public shall be designed so that exposed nuts or bolts cannot be readily removed, permitting access to live parts;
(D) Where nonmetallic or metal-enclosed
equipment is accessible to the general public
and the bottom of the enclosure is less than
2.44 m (8.0 ft) above the floor or grade level,
the enclosure door or hinged cover shall be
kept locked; and
(E) Except for underground box covers that
weigh over 45.4 kg (100 lb), doors and covers
of enclosures used solely as pull boxes, splice
boxes, or junction boxes shall be locked,
bolted, or screwed on.
(3) Work space about equipment. Sufficient
space shall be provided and maintained
about electric equipment to permit ready
and safe operation and maintenance of such
equipment. Where energized parts are exposed, the minimum clear work space may
not be less than 1.98 m (6.5 ft) high (measured
vertically from the floor or platform) or less
than 914 mm (3.0 ft) wide (measured parallel
to the equipment). The depth shall be as required in paragraph (h)(5)(i) of this section.
In all cases, the work space shall be adequate
to permit at least a 90-degree opening of
doors or hinged panels.
(4) Entrance and access to work space. (i) At
least one entrance not less than 610 mm (24
in.) wide and 1.98 m (6.5 ft) high shall be provided to give access to the working space
about electric equipment.
(A) On switchboard and control panels exceeding 1.83 m (6.0 ft) in width, there shall be
one entrance at each end of such boards unless the location of the switchboards and
control panels permits a continuous and unobstructed way of exit travel, or unless the
work space required in paragraph (h)(5)(i) of
this section is doubled.
(B) Where one entrance to the working
space is permitted under the conditions described in paragraph (h)(4)(i)(A) of this section, the entrance shall be located so that
the edge of the entrance nearest the switchboards and control panels is at least the minimum clear distance given in Table S–2 away
from such equipment.
(C) Where bare energized parts at any voltage or insulated energized parts above 600
volts, nominal, to ground are located adjacent to such entrance, they shall be suitably
guarded.
(ii) Permanent ladders or stairways shall
be provided to give safe access to the working space around electric equipment installed on platforms, balconies, mezzanine
floors, or in attic or roof rooms or spaces.
§ 1910.303
(5) Working space and guarding. (i)(vi) Except as elsewhere required or permitted in
this subpart, the minimum clear working
space in the direction of access to live parts
of electric equipment may not be less than
specified in Table S–2. Distances shall be
measured from the live parts, if they are exposed, or from the enclosure front or opening, if they are enclosed.
(ii) If switches, cutouts, or other equipment operating at 600 volts, nominal, or less,
are installed in a room or enclosure where
there are exposed live parts or exposed wiring operating at over 600 volts, nominal, the
high-voltage equipment shall be effectively
separated from the space occupied by the
low-voltage equipment by a suitable partition, fence, or screen. However, switches or
other equipment operating at 600 volts,
nominal, or less, and serving only equipment
within the high-voltage vault, room, or enclosure may be installed in the high-voltage
enclosure, room, or vault if accessible to
qualified persons only.
(iii) The following requirements apply to
the entrances to all buildings, rooms, or enclosures containing exposed live parts or exposed conductors operating at over 600 volts,
nominal:
(A) The entrances shall be kept locked unless they are under the observation of a
qualified person at all times; and
(B) Permanent and conspicuous warning
signs shall be provided, reading substantially
as follows:
‘‘DANGER—HIGH VOLTAGE—KEEP OUT.’’
(iv) Illumination shall be provided for all
working spaces about electric equipment.
(A) The lighting outlets shall be arranged
so that persons changing lamps or making
repairs on the lighting system will not be endangered by live parts or other equipment.
(B) The points of control shall be located
so that persons are prevented from contacting any live part or moving part of the
equipment while turning on the lights.
(v) Unguarded live parts above working
space shall be maintained at elevations not
less than specified in Table S–3.
(vi) Pipes or ducts that are foreign to the
electrical installation and that require periodic maintenance or whose malfunction
would endanger the operation of the electrical system may not be located in the vicinity of service equipment, metal-enclosed
power switchgear, or industrial control assemblies. Protection shall be provided where
necessary to avoid damage from condensation leaks and breaks in such foreign systems.
(h)(5)(vi) OF THIS SECfacilities are not considered foreign if provided for fire protection
of the electrical installation.
NOTE TO PARAGRAPH
TION: Piping and other
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§ 1910.304
29 CFR Ch. XVII (7–1–07 Edition)
TABLE S–2—MINIMUM DEPTH OF CLEAR WORKING SPACE AT ELECTRIC EQUIPMENT, OVER 600 V
Minimum clear distance for condition 2 3
Nominal voltage to ground
Condition A
m
601–2500 V ...................................................................
2501–9000 V .................................................................
9001 V–25 kV ...............................................................
Over 25–75 kV 1 ............................................................
Above 75 kV 1 ...............................................................
Condition B
ft
0.9
1.2
1.5
1.8
2.5
m
3.0
4.0
5.0
6.0
8.0
Condition C
ft
1.2
1.5
1.8
2.5
3.0
m
4.0
5.0
6.0
8.0
10.0
ft
1.5
1.8
2.8
3.0
3.7
5.0
6.0
9.0
10.0
12.0
Notes to Table S–2:
1 Minimum depth of clear working space in front of electric equipment with a nominal voltage to ground above 25,000 volts
may be the same as that for 25,000 volts under Conditions A, B, and C for installations built before April 16, 1981.
2 Conditions A, B, and C are as follows:
Condition A—Exposed live parts on one side and no live or grounded parts on the other side of the working space, or exposed
live parts on both sides effectively guarded by suitable wood or other insulating material. Insulated wire or insulated busbars operating at not over 300 volts are not considered live parts.
Condition B—Exposed live parts on one side and grounded parts on the other side. Concrete, brick, and tile walls are considered as grounded surfaces.
Condition C—Exposed live parts on both sides of the work space (not guarded as provided in Condition A) with the operator
between.
3 Working space is not required in back of equipment such as dead-front switchboards or control assemblies that has no renewable or adjustable parts (such as fuses or switches) on the back and where all connections are accessible from locations
other than the back. Where rear access is required to work on the deenergized parts on the back of enclosed equipment, a minimum working space 762 mm (30 in.) horizontally shall be provided.
TABLE S–3—ELEVATION OF UNGUARDED LIVE
PARTS ABOVE WORKING SPACE
Elevation
Nominal voltage
between phases
601–7500 V ..........
7501 V–35 kV .......
Over 35 kV ...........
m
1 2.81
ft
....................
2.8 ........................
2.8 + 9.5 mm/kV
over 35 kV.
1 9.01.
9.0.
9.0 + 0.37 in./kV
over 35 kV.
1 The minimum elevation may be 2.6 m (8.5 ft) for installations built before August 13, 2007. The minimum elevation
may be 2.4 m (8.0 ft) for installations built before April 16,
1981, if the nominal voltage between phases is in the range
of 601–6600 volts.
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§ 1910.304
tion.
Wiring design and protec-
(a) Use and identification of grounded
and grounding conductors—(1) Identification of conductors. A conductor used as
a grounded conductor shall be identifiable and distinguishable from all other
conductors. A conductor used as an
equipment grounding conductor shall
be identifiable and distinguishable
from all other conductors.
(2) Polarity of connections. No grounded conductor may be attached to any
terminal or lead so as to reverse designated polarity.
(3) Use of grounding terminals and devices. A grounding terminal or grounding-type device on a receptacle, cord
connector, or attachment plug may not
be used for purposes other than grounding.
(b) Branch circuits—(1) [Reserved]
(2) Outlet devices. Outlet devices shall
have an ampere rating not less than
the load to be served.
(c) Outside conductors, 600 volts, nominal, or less. Paragraphs (c)(1), (c)(2),
(c)(3), and (c)(4) of this section apply to
branch circuit, feeder, and service conductors rated 600 volts, nominal, or less
and run outdoors as open conductors.
Paragraph (c)(5) applies to lamps installed under such conductors.
(1) Conductors on poles. Conductors
supported on poles shall provide a horizontal climbing space not less than the
following:
(i) Power conductors below communication conductors—30 inches.
(ii) Power conductors alone or above
communication conductors: 300 volts or
less—24 inches; more than 300 volts—30
inches.
(iii)
Communication
conductors
below power conductors with power
conductors 300 volts or less—24 inches;
more than 300 volts—30 inches.
(2) Clearance from ground. Open conductors shall conform to the following
minimum clearances:
(i) 10 feet—above finished grade, sidewalks, or from any platform or projection from which they might be reached.
(ii) 12 feet—over areas subject to vehicular traffic other than truck traffic.
(iii) 15 feet—over areas other than
those specified in paragraph (c)(2)(iv) of
this section that are subject to truck
traffic.
842
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§ 1910.305
29 CFR Ch. XVII (7–1–07 Edition)
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(9) Grounding of systems and circuits of 1000
volts and over (high voltage). If high voltage
systems are grounded, they shall comply
with all applicable provisions of paragraphs
(g)(1) through (g)(8) of this section as supplemented and modified by the following requirements:
(i) Systems supplying portable or mobile
high voltage equipment, other than substations installed on a temporary basis, shall
comply with the following:
(A) The system shall have its neutral
grounded through an impedance. If a deltaconnected high voltage system is used to
supply the equipment, a system neutral shall
be derived.
(B) Exposed noncurrent-carrying metal
parts of portable and mobile equipment shall
be connected by an equipment grounding
conductor to the point at which the system
neutral impedance is grounded.
(C) Ground-fault detection and relaying
shall be provided to automatically deenergize any high voltage system component
that has developed a ground fault. The continuity of the equipment grounding conductor shall be continuously monitored so as
to deenergize automatically the high voltage
feeder to the portable equipment upon loss of
continuity of the equipment grounding conductor.
(D) The grounding electrode to which the
portable equipment system neutral impedance is connected shall be isolated from and
separated in the ground by at least 6.1 m
(20.0 ft) from any other system or equipment
grounding electrode, and there shall be no direct connection between the grounding electrodes, such as buried pipe, fence, and so
forth.
(ii) All noncurrent-carrying metal parts of
portable equipment and fixed equipment, including their associated fences, housings, enclosures, and supporting structures, shall be
grounded. However, equipment that is guarded by location and isolated from ground need
not be grounded. Additionally, pole-mounted
distribution apparatus at a height exceeding
2.44 m (8.0 ft) above ground or grade level
need not be grounded.
§ 1910.305 Wiring
methods,
components, and equipment for general
use.
(a) Wiring methods. The provisions of
this section do not apply to the conductors that are an integral part of factory-assembled equipment.
(1) General requirements—(i) Electrical
continuity of metal raceways and enclosures. Metal raceways, cable armor, and
other metal enclosures for conductors
shall be metallically joined together
into a continuous electric conductor
and shall be so connected to all boxes,
fittings, and cabinets as to provide effective electrical continuity.
(ii) Wiring in ducts. No wiring systems
of any type shall be installed in ducts
used to transport dust, loose stock or
flammable vapors. No wiring system of
any type may be installed in any duct
used for vapor removal or for ventilation of commercial-type cooking equipment, or in any shaft containing only
such ducts.
(2) Temporary wiring. Temporary electrical power and lighting wiring methods may be of a class less than would
be required for a permanent installation. Except as specifically modified in
this paragraph, all other requirements
of this subpart for permanent wiring
shall apply to temporary wiring installations.
(i) Uses permitted, 600 volts, nominal, or
less. Temporary electrical power and
lighting installations 600 volts, nominal, or less may be used only:
(A) During and for remodeling, maintenance, repair, or demolition of buildings, structures, or equipment, and
similar activities;
(B) For experimental or development
work, and
(C) For a period not to exceed 90 days
for Christmas decorative lighting, carnivals, and similar purposes.
(ii) Uses permitted, over 600 volts, nominal. Temporary wiring over 600 volts,
nominal, may be used only during periods of tests, experiments, or emergencies.
(iii) General requirements for temporary
wiring. (A) Feeders shall originate in an
approved distribution center. The conductors shall be run as multiconductor
cord or cable assemblies, or, where not
subject to physical damage, they may
be run as open conductors on
insulators not more than 10 feet apart.
(B) Branch circuits shall originate in
an approved power outlet or panelboard. Conductors shall be multiconductor cord or cable assemblies or open
conductors. If run as open conductors
they shall be fastened at ceiling height
every 10 feet. No branch-circuit conductor may be laid on the floor. Each
branch circuit that supplies receptacles
or fixed equipment shall contain a separate equipment grounding conductor
if run as open conductors.
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(C) Receptacles shall be of the
grounding type. Unless installed in a
complete
metallic
raceway,
each
branch circuit shall contain a separate
equipment grounding conductor and all
receptacles shall be electrically connected to the grounding conductor.
(D) No bare conductors nor earth returns may be used for the wiring of any
temporary circuit.
(E) Suitable disconnecting switches
or plug connectors shall be installed to
permit the disconnection of all
ungrounded conductors of each temporary circuit.
(F) Lamps for general illumination
shall be protected from accidental contact or breakage. Protection shall be
provided by elevation of at least 7 feet
from normal working surface or by a
suitable fixture or lampholder with a
guard.
(G) Flexible cords and cables shall be
protected from accidental damage.
Sharp corners and projections shall be
avoided. Where passing through doorways or other pinch points, flexible
cords and cables shall be provided with
protection to avoid damage.
(3) Cable trays—(i) Uses permitted. (a)
Only the following may be installed in
cable tray systems:
(1) Mineral-insulated metal-sheathed
cable (Type MI);
(2) Armored cable (Type AC);
(3) Metal-clad cable (Type MC);
(4) Power-limited tray cable (Type
PLTC);
(5) Nonmetallic-sheathed cable (Type
NM or NMC);
(6) Shielded nonmetallic-sheathed
cable (Type SNM);
(7) Multiconductor service-entrance
cable (Type SE or USE);
(8) Multiconductor underground feeder and branch-circuit cable (Type UF);
(9) Power and control tray cable
(Type TC);
(10) Other factory-assembled, multiconductor control, signal, or power cables which are specifically approved for
installation in cable trays; or
(11) Any approved conduit or raceway
with its contained conductors.
(b) In industrial establishments only,
where conditions of maintenance and
supervision assure that only qualified
persons will service the installed cable
tray system, the following cables may
§ 1910.305
also be installed in ladder, ventilated
trough, or 4 inch ventilated channeltype cable trays:
(1) Single conductor cables which are
250 MCM or larger and are Types RHH,
RHW, MV, USE, or THW, and other 250
MCM or larger single conductor cables
if specifically approved for installation
in cable trays. Where exposed to direct
rays of the sun, cables shall be sunlight-resistant.
(2) Type MV cables, where exposed to
direct rays of the sun, shall be sunlight-resistant.
(c) Cable trays in hazardous (classified) locations shall contain only the
cable types permitted in such locations.
(ii) Uses not permitted. Cable tray systems may not be used in hoistways or
where subjected to severe physical
damage.
(4) Open wiring on insulators—(i) Uses
permitted. Open wiring on insulators is
only permitted on systems of 600 volts,
nominal, or less for industrial or agricultural establishments and for services.
(ii) Conductor supports. Conductors
shall be rigidly supported on noncombustible, nonabsorbent insulating
materials and may not contact any
other objects.
(iii) Flexible nonmetallic tubing. In dry
locations where not exposed to severe
physical damage, conductors may be
separately enclosed in flexible nonmetallic tubing. The tubing shall be in
continuous lengths not exceeding 15
feet and secured to the surface by
straps at intervals not exceeding 4 feet
6 inches.
(iv) Through walls, floors, wood cross
members, etc. Open conductors shall be
separated from contact with walls,
floors, wood cross members, or partitions through which they pass by tubes
or bushings of noncombustible, nonabsorbent insulating material. If the
bushing is shorter than the hole, a waterproof sleeve of nonconductive material shall be inserted in the hole and an
insulating bushing slipped into the
sleeve at each end in such a manner as
to keep the conductors absolutely out
of contact with the sleeve. Each conductor shall be carried through a separate tube or sleeve.
855
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29 CFR Ch. XVII (7–1–07 Edition)
(v) Protection from physical damage.
Conductors within 7 feet from the floor
are considered exposed to physical
damage. Where open conductors cross
ceiling joints and wall studs and are
exposed to physical damage, they shall
be protected.
(b) Cabinets, boxes, and fittings—(1)
Conductors entering boxes, cabinets, or
fittings. Conductors entering boxes,
cabinets, or fittings shall also be protected from abrasion, and openings
through which conductors enter shall
be effectively closed. Unused openings
in cabinets, boxes, and fittings shall be
effectively closed.
(2) Covers and canopies. All pull boxes,
junction boxes, and fittings shall be
provided with covers approved for the
purpose. If metal covers are used they
shall be grounded. In completed installations each outlet box shall have a
cover, faceplate, or fixture canopy.
Covers of outlet boxes having holes
through which flexible cord pendants
pass shall be provided with bushings
designed for the purpose or shall have
smooth, well-rounded surfaces on
which the cords may bear.
(3) Pull and junction boxes for systems
over 600 volts, nominal. In addition to
other requirements in this section for
pull and junction boxes, the following
shall apply to these boxes for systems
over 600 volts, nominal:
(i) Boxes shall provide a complete enclosure for the contained conductors or
cables.
(ii) Boxes shall be closed by suitable
covers securely fastened in place. Underground box covers that weigh over
100 pounds meet this requirement. Covers for boxes shall be permanently
marked ‘‘HIGH VOLTAGE.’’ The marking shall be on the outside of the box
cover and shall be readily visible and
legible.
(c) Switches—(1) Knife switches. Single-throw knife switches shall be so
connected that the blades are dead
when the switch is in the open position. Single-throw knife switches shall
be so placed that gravity will not tend
to close them. Single-throw knife
switches approved for use in the inverted position shall be provided with a
locking device that will ensure that
the blades remain in the open position
when so set. Double-throw knife
switches may be mounted so that the
throw will be either vertical or horizontal. However, if the throw is
vertical a locking device shall be provided to ensure that the blades remain
in the open position when so set.
(2) Faceplates for flush-mounted snap
switches. Flush snap switches that are
mounted in ungrounded metal boxes
and located within reach of conducting
floors or other conducting surfaces
shall be provided with faceplates of
nonconducting, noncombustible material.
(d) Switchboards and panelboards.
Switchboards that have any exposed
live parts shall be located in permanently dry locations and accessible
only to qualified persons. Panelboards
shall be mounted in cabinets, cutout
boxes, or enclosures approved for the
purpose and shall be dead front. However, panelboards other than the dead
front externally-operable type are permitted where accessible only to qualified persons. Exposed blades of knife
switches shall be dead when open.
(e) Enclosures for damp or wet locations. (1) Cabinets, cutout boxes, fittings, boxes, and panelboard enclosures
in damp or wet locations shall be installed so as to prevent moisture or
water from entering and accumulating
within the enclosures. In wet locations
the enclosures shall be weatherproof.
(2) Switches, circuit breakers, and
switchboards installed in wet locations
shall be enclosed in weatherproof enclosures.
(f) Conductors for general wiring. All
conductors used for general wiring
shall be insulated unless otherwise permitted in this Subpart. The conductor
insulation shall be of a type that is approved for the voltage, operating temperature, and location of use. Insulated
conductors shall be distinguishable by
appropriate color or other suitable
means as being grounded conductors,
ungrounded conductors, or equipment
grounding conductors.
(g) Flexible cords and cables—(1) Use of
flexible cords and cables. (i) Flexible
cords and cables shall be approved and
suitable for conditions of use and location. Flexible cords and cables shall be
used only for:
(A) Pendants;
(B) Wiring of fixtures;
856
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(C) Connection of portable lamps or
appliances;
(D) Elevator cables;
(E) Wiring of cranes and hoists;
(F) Connection of stationary equipment to facilitate their frequent interchange;
(G) Prevention of the transmission of
noise or vibration;
(H) Appliances where the fastening
means and mechanical connections are
designed to permit removal for maintenance and repair; or
(I) Data processing cables approved
as a part of the data processing system.
(ii) If used as permitted in paragraphs
(g)(1)(i)(c),
(g)(1)(i)(f),
or
(g)(1)(i)(h) of this section, the flexible
cord shall be equipped with an attachment plug and shall be energized from
an approved receptacle outlet.
(iii) Unless specifically permitted in
paragraph (g)(1)(i) of this section, flexible cords and cables may not be used:
(A) As a substitute for the fixed wiring of a structure;
(B) Where run through holes in walls,
ceilings, or floors;
(C) Where run through doorways,
windows, or similar openings;
(D) Where attached to building surfaces; or
(E) Where concealed behind building
walls, ceilings, or floors.
(iv) Flexible cords used in show windows and showcases shall be Type S,
SO, SJ, SJO, ST, STO, SJT, SJTO, or
AFS except for the wiring of chain-supported lighting fixtures and supply
cords for portable lamps and other
merchandise being displayed or exhibited.
(2) Identification, splices, and terminations. (i) A conductor of a flexible
cord or cable that is used as a grounded
conductor or an equipment grounding
conductor shall be distinguishable
from other conductors. Types SJ, SJO,
SJT, SJTO, S, SO, ST, and STO shall
be durably marked on the surface with
the type designation, size, and number
of conductors.
(ii) Flexible cords shall be used only
in continuous lengths without splice or
tap. Hard service flexible cords No. 12
or larger may be repaired if spliced so
that the splice retains the insulation,
outer sheath properties, and usage
§ 1910.305
characteristics of the cord being
spliced.
(iii) Flexible cords shall be connected
to devices and fittings so that strain
relief is provided which will prevent
pull from being directly transmitted to
joints or terminal screws.
(h) Portable cables over 600 volts, nominal. Multiconductor portable cable for
use in supplying power to portable or
mobile equipment at over 600 volts,
nominal, shall consist of No. 8 or larger
conductors employing flexible stranding. Cables operated at over 2,000 volts
shall be shielded for the purpose of confining the voltage stresses to the insulation. Grounding conductors shall be
provided. Connectors for these cables
shall be of a locking type with provisions to prevent their opening or closing while energized. Strain relief shall
be provided at connections and terminations. Portable cables may not be operated with splices unless the splices
are of the permanent molded, vulcanized, or other approved type. Termination enclosures shall be suitably
marked with a high voltage hazard
warning, and terminations shall be accessible only to authorized and qualified personnel.
(i) Fixture wires—(1) General. Fixture
wires shall be approved for the voltage,
temperature, and location of use. A fixture wire which is used as a grounded
conductor shall be identified.
(2) Uses permitted. Fixture wires may
be used:
(i) For installation in lighting fixtures and in similar equipment where
enclosed or protected and not subject
to bending or twisting in use; or
(ii) For connecting lighting fixtures
to the branch-circuit conductors supplying the fixtures.
(3) Uses not permitted. Fixture wires
may not be used as branch-circuit conductors except as permitted for Class 1
power limited circuits.
(j) Equipment for general use—(1)
Lighting fixtures, lampholders, lamps,
and
receptacles.
(i)
Fixtures,
lampholders, lamps, rosettes, and receptacles may have no live parts normally exposed to employee contact.
However,
rosettes
and
cleat-type
lampholders and receptacles located at
least 8 feet above the floor may have
exposed parts.
857
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§ 1910.305
29 CFR Ch. XVII (7–1–07 Edition)
(ii) Handlamps of the portable type
supplied through flexible cords shall be
equipped with a handle of molded composition or other material approved for
the purpose, and a substantial guard
shall be attached to the lampholder or
the handle.
(iii) Lampholders of the screw-shell
type shall be installed for use as
lampholders only. Lampholders installed in wet or damp locations shall
be of the weatherproof type.
(iv) Fixtures installed in wet or damp
locations shall be approved for the purpose and shall be so constructed or installed that water cannot enter or accumulate in wireways, lampholders, or
other electrical parts.
(2) Receptacles, cord connectors, and attachment plugs (caps). (i) Receptacles,
cord connectors, and attachment plugs
shall be constructed so that no receptacle or cord connector will accept an
attachment plug with a different voltage or current rating than that for
which the device is intended. However,
a 20-ampere T-slot receptacle or cord
connector may accept a 15-ampere attachment plug of the same voltage rating.
(ii) A receptacle installed in a wet or
damp location shall be suitable for the
location.
(3) Appliances. (i) Appliances, other
than those in which the current-carrying parts at high temperatures are
necessarily exposed, may have no live
parts normally exposed to employee
contact.
(ii) A means shall be provided to disconnect each appliance.
(iii) Each appliance shall be marked
with its rating in volts and amperes or
volts and watts.
(4) Motors. This paragraph applies to
motors, motor circuits, and controllers.
(i) In sight from. If specified that one
piece of equipment shall be ‘‘in sight
from’’ another piece of equipment, one
shall be visible and not more than 50
feet from the other.
(ii) Disconnecting means. (A) A disconnecting means shall be located in
sight from the controller location.
However, a single disconnecting means
may be located adjacent to a group of
coordinated controllers mounted adjacent to each other on a multi-motor
continuous process machine. The controller disconnecting means for motor
branch circuits over 600 volts, nominal,
may be out of sight of the controller, if
the controller is marked with a warning label giving the location and identification of the disconnecting means
which is to be locked in the open position.
(B) The disconnecting means shall
disconnect the motor and the controller from all ungrounded supply conductors and shall be so designed that
no pole can be operated independently.
(C) If a motor and the driven machinery are not in sight from the controller
location, the installation shall comply
with one of the following conditions:
(1) The controller disconnecting
means shall be capable of being locked
in the open position.
(2) A manually operable switch that
will disconnect the motor from its
source of supply shall be placed in
sight from the motor location.
(D) The disconnecting means shall
plainly indicate whether it is in the
open (off) or closed (on) position.
(E) The disconnecting means shall be
readily accessible. If more than one
disconnect is provided for the same
equipment, only one need be readily
accessible.
(F) An individual disconnecting
means shall be provided for each
motor, but a single disconnecting
means may be used for a group of motors under any one of the following
conditions:
(1) If a number of motors drive special parts of a single machine or piece
of apparatus, such as a metal or woodworking machine, crane, or hoist;
(2) If a group of motors is under the
protection of one set of branch-circuit
protective devices; or
(3) If a group of motors is in a single
room in sight from the location of the
disconnecting means.
(iii) Motor overload, short-circuit, and
ground-fault protection. Motors, motorcontrol apparatus, and motor branchcircuit conductors shall be protected
against overheating due to motor overloads or failure to start, and against
short-circuits or ground faults. These
provisions shall not require overload
protection that will stop a motor
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where a shutdown is likely to introduce additional or increased hazards,
as in the case of fire pumps, or where
continued operation of a motor is necessary for a safe shutdown of equipment or process and motor overload
sensing devices are connected to a supervised alarm.
(iv) Protection of live parts—all
voltages. (A) Stationary motors having
commutators, collectors, and brush
rigging located inside of motor end
brackets and not conductively connected to supply circuits operating at
more than 150 volts to ground need not
have such parts guarded. Exposed live
parts of motors and controllers operating at 50 volts or more between terminals shall be guarded against accidental contact by any of the following:
(1) By installation in a room or enclosure that is accessible only to qualified persons;
(2) By installation on a suitable balcony, gallery, or platform, so elevated
and arranged as to exclude unqualified
persons; or
(3) By elevation 8 feet or more above
the floor.
(B) Where live parts of motors or controllers operating at over 150 volts to
ground are guarded against accidental
contact only by location, and where adjustment or other attendance may be
necessary during the operation of the
apparatus, suitable insulating mats or
platforms shall be provided so that the
attendant cannot readily touch live
parts unless standing on the mats or
platforms.
(5) Transformers. (i) The following
paragraphs cover the installation of all
transformers except the following:
(A) Current transformers;
(B) Dry-type transformers installed
as a component part of other apparatus;
(C) Transformers which are an integral part of an X-ray, high frequency,
or electrostatic-coating apparatus;
(D) Transformers used with Class 2
and Class 3 circuits, sign and outline
lighting, electric discharge lighting,
and power-limited fire-protective signalling circuits; and
(E) Liquid-filled or dry-type transformers used for research, development, or testing, where effective safeguard arrangements are provided.
§ 1910.305
(ii) The operating voltage of exposed
live parts of transformer installations
shall be indicated by warning signs or
visible markings on the equipment or
structure.
(iii) Dry-type, high fire point liquidinsulated, and askarel-insulated transformers installed indoors and rated
over 35kV shall be in a vault.
(iv) If they present a fire hazard to
employees, oil-insulated transformers
installed indoors shall be in a vault.
(v) Combustible material, combustible buildings and parts of buildings,
fire escapes, and door and window
openings shall be safeguarded from
fires which may originate in oil-insulated transformers attached to or adjacent to a building or combustible material.
(vi) Transformer vaults shall be constructed so as to contain fire and combustible liquids within the vault and to
prevent unauthorized access. Locks
and latches shall be so arranged that a
vault door can be readily opened from
the inside.
(vii) Any pipe or duct system foreign
to the vault installation may not enter
or pass through a transformer vault.
(viii) Materials may not be stored in
transformer vaults.
(6) Capacitors. (i) All capacitors, except surge capacitors or capacitors included as a component part of other apparatus, shall be provided with an
automatic means of draining the stored
charge after the capacitor is disconnected from its source of supply.
(ii) Capacitors rated over 600 volts,
nominal, shall comply with the following additional requirements:
(A) Isolating or disconnecting switches (with no interrupting rating) shall
be interlocked with the load interrupting device or shall be provided
with prominently displayed caution
signs to prevent switching load current.
(B)
For
series
capacitors
(see
§ 1910.302(b)(3)), the proper switching
shall be assured by use of at least one
of the following:
(1) Mechanically sequenced isolating
and bypass switches,
(2) Interlocks, or
(3) Switching procedure prominently
displayed at the switching location.
859
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§ 1910.305
29 CFR Ch. XVII (7–1–07 Edition)
(7) Storage batteries. Provisions shall
be made for sufficient diffusion and
ventilation of gases from storage batteries to prevent the accumulation of
explosive mixtures.
[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7,
1981]
EFFECTIVE DATE NOTE: At 72 FR 7201, Feb.
14, 2007, § 1910.305 was revised, effective Aug.
13, 2007. For the convenience of the user, the
revised text is set forth as follows:
rfrederick on PROD1PC67 with CFR
§ 1910.305 Wiring methods, components, and
equipment for general use.
(a) Wiring methods. The provisions of this
section do not apply to conductors that are
an integral part of factory-assembled equipment.
(1) General requirements. (i) Metal raceways,
cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal noncurrent-carrying parts that are to serve as
grounding conductors, with or without the
use of supplementary equipment grounding
conductors, shall be effectively bonded where
necessary to ensure electrical continuity and
the capacity to conduct safely any fault current likely to be imposed on them. Any nonconductive paint, enamel, or similar coating
shall be removed at threads, contact points,
and contact surfaces or be connected by
means of fittings designed so as to make
such removal unnecessary.
(ii) Where necessary for the reduction of
electrical noise (electromagnetic interference) of the grounding circuit, an equipment enclosure supplied by a branch circuit
may be isolated from a raceway containing
circuits supplying only that equipment by
one or more listed nonmetallic raceway fittings located at the point of attachment of
the raceway to the equipment enclosure. The
metal raceway shall be supplemented by an
internal insulated equipment grounding conductor installed to ground the equipment enclosure.
(iii) No wiring systems of any type may be
installed in ducts used to transport dust,
loose stock, or flammable vapors. No wiring
system of any type may be installed in any
duct used for vapor removal or for ventilation of commercial-type cooking equipment,
or in any shaft containing only such ducts.
(2) Temporary wiring. Except as specifically
modified in this paragraph, all other requirements of this subpart for permanent wiring
shall also apply to temporary wiring installations.
(i) Temporary electrical power and lighting installations of 600 volts, nominal, or less
may be used only as follows:
(A) During and for remodeling, maintenance, or repair of buildings, structures, or
equipment, and similar activities;
(B) For a period not to exceed 90 days for
Christmas decorative lighting, carnivals, and
similar purposes; or
(C) For experimental or development work,
and during emergencies.
(ii) Temporary wiring shall be removed immediately upon completion of the project or
purpose for which the wiring was installed.
(iii) Temporary electrical installations of
more than 600 volts may be used only during
periods of tests, experiments, emergencies,
or construction-like activities.
(iv) The following requirements apply to
feeders:
(A) Feeders shall originate in an approved
distribution center.
(B) Conductors shall be run as multiconductor cord or cable assemblies. However, if
installed
as
permitted
in
paragraph
(a)(2)(i)(C) of this section, and if accessible
only to qualified persons, feeders may be run
as single insulated conductors.
(v) The following requirements apply to
branch circuits:
(A) Branch circuits shall originate in an
approved power outlet or panelboard.
(B) Conductors shall be multiconductor
cord or cable assemblies or open conductors.
If run as open conductors, they shall be fastened at ceiling height every 3.05 m (10.0 ft).
(C) No branch-circuit conductor may be
laid on the floor.
(D) Each branch circuit that supplies receptacles or fixed equipment shall contain a
separate equipment grounding conductor if
run as open conductors.
(vi) Receptacles shall be of the grounding
type. Unless installed in a continuous
grounded metallic raceway or metallic covered cable, each branch circuit shall contain
a separate equipment grounding conductor
and all receptacles shall be electrically connected to the grounding conductor.
(vii) No bare conductors nor earth returns
may be used for the wiring of any temporary
circuit.
(viii) Suitable disconnecting switches or
plug connectors shall be installed to permit
the disconnection of all ungrounded conductors of each temporary circuit. Multiwire
branch circuits shall be provided with a
means to disconnect simultaneously all
ungrounded conductors at the power outlet
or panelboard where the branch circuit originated.
NOTE TO PARAGRAPH (a)(2)(viii) OF THIS SECTION. Circuit breakers with their handles
connected by approved handle ties are considered a single disconnecting means for the
purpose of this requirement.
(ix) All lamps for general illumination
shall be protected from accidental contact or
breakage by a suitable fixture or lampholder
with a guard. Brass shell, paper-lined sockets, or other metal-cased sockets may not be
used unless the shell is grounded.
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(x) Flexible cords and cables shall be protected from accidental damage, as might be
caused, for example, by sharp corners, projections, and doorways or other pinch points.
(xi) Cable assemblies and flexible cords and
cables shall be supported in place at intervals that ensure that they will be protected
from physical damage. Support shall be in
the form of staples, cables ties, straps, or
similar type fittings installed so as not to
cause damage.
(3) Cable trays. (i) Only the following wiring
methods may be installed in cable tray systems: armored cable; electrical metallic tubing; electrical nonmetallic tubing; fire alarm
cables; flexible metal conduit; flexible metallic tubing; instrumentation tray cable; intermediate metal conduit; liquidtight flexible metal conduit; liquidtight flexible nonmetallic conduit; metal-clad cable; mineralinsulated, metal-sheathed cable; multiconductor service-entrance cable; multiconductor underground feeder and branch-circuit cable; multipurpose and communications cables; nonmetallic-sheathed cable;
power and control tray cable; power-limited
tray cable; optical fiber cables; and other
factory-assembled, multiconductor control,
signal, or power cables that are specifically
approved for installation in cable trays, rigid
metal conduit, and rigid nonmetallic conduit.
(ii) In industrial establishments where conditions of maintenance and supervision assure that only qualified persons will service
the installed cable tray system, the following cables may also be installed in ladder, ventilated-trough, or ventilated-channel
cable trays:
(A) Single conductor cable; the cable shall
be No. 1/0 or larger and shall be of a type listed and marked on the surface for use in cable
trays; where Nos. 1/0 through 4/0 single conductor cables are installed in ladder cable
tray, the maximum allowable rung spacing
for the ladder cable tray shall be 229 mm (9
in.); where exposed to direct rays of the sun,
cables shall be identified as being sunlight
resistant;
(B) Welding cables installed in dedicated
cable trays;
(C) Single conductors used as equipment
grounding conductors; these conductors,
which may be insulated, covered, or bare,
shall be No. 4 or larger; and
(D) Multiconductor cable, Type MV; where
exposed to direct rays of the sun, the cable
shall be identified as being sunlight resistant.
(iii) Metallic cable trays may be used as
equipment grounding conductors only where
continuous maintenance and supervision ensure that qualified persons will service the
installed cable tray system.
(iv) Cable trays in hazardous (classified) locations may contain only the cable types
permitted in such locations. (See § 1910.307.)
§ 1910.305
(v) Cable tray systems may not be used in
hoistways or where subjected to severe physical damage.
(4) Open wiring on insulators. (i) Open wiring on insulators is only permitted on systems of 600 volts, nominal, or less for industrial or agricultural establishments, indoors
or outdoors, in wet or dry locations, where
subject to corrosive vapors, and for services.
(ii) Conductors smaller than No. 8 shall be
rigidly supported on noncombustible, nonabsorbent insulating materials and may not
contact any other objects. Supports shall be
installed as follows:
(A) Within 152 mm (6 in.) from a tap or
splice;
(B) Within 305 mm (12 in.) of a dead-end
connection to a lampholder or receptacle;
and
(C) At intervals not exceeding 1.37 m (4.5
ft), and at closer intervals sufficient to provide adequate support where likely to be disturbed.
(iii) In dry locations, where not exposed to
severe physical damage, conductors may be
separately enclosed in flexible nonmetallic
tubing. The tubing shall be in continuous
lengths not exceeding 4.57 m (15.0 ft) and secured to the surface by straps at intervals
not exceeding 1.37 m (4.5 ft).
(iv) Open conductors shall be separated
from contact with walls, floors, wood cross
members, or partitions through which they
pass by tubes or bushings of noncombustible,
nonabsorbent insulating material. If the
bushing is shorter than the hole, a waterproof sleeve of nonconductive material shall
be inserted in the hole and an insulating
bushing slipped into the sleeve at each end in
such a manner as to keep the conductors absolutely out of contact with the sleeve. Each
conductor shall be carried through a separate tube or sleeve.
(v) Where open conductors cross ceiling
joints and wall studs and are exposed to
physical damage (for example, located within 2.13 m (7.0 ft) of the floor), they shall be
protected.
(b) Cabinets, boxes, and fittings—(1) Conductors entering boxes, cabinets, or fittings. (i)
Conductors entering cutout boxes, cabinets,
or fittings shall be protected from abrasion,
and openings through which conductors
enter shall be effectively closed.
(ii) Unused openings in cabinets, boxes, and
fittings shall be effectively closed.
(iii) Where cable is used, each cable shall
be secured to the cabinet, cutout box, or
meter socket enclosure. However, where
cable with an entirely nonmetallic sheath
enters the top of a surface-mounted enclosure through one or more nonflexible raceways not less than 457 mm (18 in.) or more
than 3.05 m (10.0 ft) in length, the cable need
not be secured to the cabinet, box, or enclosure provided all of the following conditions
are met:
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§ 1910.305
29 CFR Ch. XVII (7–1–07 Edition)
(A) Each cable is fastened within 305 mm
(12 in.) of the outer end of the raceway,
measured along the sheath;
(B) The raceway extends directly above the
enclosure and does not penetrate a structural ceiling;
(C) A fitting is provided on each end of the
raceway to protect the cable from abrasion,
and the fittings remain accessible after installation;
(D) The raceway is sealed or plugged at the
outer end using approved means so as to prevent access to the enclosure through the
raceway;
(E) The cable sheath is continuous through
the raceway and extends into the enclosure
not less than 6.35 mm (0.25 in.) beyond the
fitting;
(F) The raceway is fastened at its outer
end and at other points as necessary; and
(G) Where installed as conduit or tubing,
the allowable cable fill does not exceed that
permitted for complete conduit or tubing
systems.
(2) Covers and canopies. (i) All pull boxes,
junction boxes, and fittings shall be provided
with covers identified for the purpose. If
metal covers are used, they shall be grounded. In completed installations, each outlet
box shall have a cover, faceplate, or fixture
canopy. Covers of outlet boxes having holes
through which flexible cord pendants pass
shall be provided with bushings designed for
the purpose or shall have smooth, wellrounded surfaces on which the cords may
bear.
(ii) Where a fixture canopy or pan is used,
any combustible wall or ceiling finish exposed between the edge of the canopy or pan
and the outlet box shall be covered with noncombustible material.
(3) Pull and junction boxes for systems over
600 volts, nominal. In addition to other requirements in this section, the following requirements apply to pull and junction boxes
for systems over 600 volts, nominal:
(i) Boxes shall provide a complete enclosure for the contained conductors or cables.
(ii) Boxes shall be closed by suitable covers
securely fastened in place.
NOTE TO PARAGRAPH (b)(3)(ii) OF THIS SECTION: Underground box covers that weigh
rfrederick on PROD1PC67 with CFR
over 45.4 kg (100 lbs) meet this requirement.
(iii) Covers for boxes shall be permanently
marked ‘‘HIGH VOLTAGE.’’ The marking
shall be on the outside of the box cover and
shall be readily visible and legible.
(c) Switches—(1) Single-throw knife switches.
Single-throw knife switches shall be so
placed that gravity will not tend to close
them. Single-throw knife switches approved
for use in the inverted position shall be provided with a locking device that will ensure
that the blades remain in the open position
when so set.
(2) Double-throw knife switches. Doublethrow knife switches may be mounted so
that the throw will be either vertical or horizontal. However, if the throw is vertical, a
locking device shall be provided to ensure
that the blades remain in the open position
when so set.
(3) Connection of switches. (i) Single-throw
knife switches and switches with butt contacts shall be connected so that the blades
are deenergized when the switch is in the
open position.
(ii) Single-throw knife switches, moldedcase switches, switches with butt contacts,
and circuit breakers used as switches shall
be connected so that the terminals supplying
the load are deenergized when the switch is
in the open position. However, blades and
terminals supplying the load of a switch may
be energized when the switch is in the open
position where the switch is connected to
circuits or equipment inherently capable of
providing a backfeed source of power. For
such installations, a permanent sign shall be
installed on the switch enclosure or immediately adjacent to open switches that read,
‘‘WARNING—LOAD SIDE TERMINALS MAY
BE ENERGIZED BY BACKFEED.’’
(4) Faceplates for flush-mounted snap switches. Snap switches mounted in boxes shall
have faceplates installed so as to completely
cover the opening and seat against the finished surface.
(5) Grounding. Snap switches, including
dimmer switches, shall be effectively
grounded and shall provide a means to
ground metal faceplates, whether or not a
metal faceplate is installed. However, if no
grounding means exists within the snapswitch enclosure, or where the wiring method does not include or provide an equipment
ground, a snap switch without a grounding
connection is permitted for replacement purposes only. Such snap switches shall be provided with a faceplate of nonconducting,
noncombustible material if they are located
within reach of conducting floors or other
conducting surfaces.
(d)
Switchboards
and
panelboards—(1)
Switchboards with exposed live parts. Switchboards that have any exposed live parts shall
be located in permanently dry locations and
shall be accessible only to qualified persons.
(2) Panelboard enclosures. Panelboards shall
be mounted in cabinets, cutout boxes, or enclosures designed for the purpose and shall
be dead front. However, panelboards other
than the dead front externally-operable type
are permitted where accessible only to qualified persons.
(3) Knife switches mounted in switchboards or
panelboards. Exposed blades of knife switches
mounted in switchboards or panelboards
shall be dead when open.
(e) Enclosures for damp or wet locations—(1)
Cabinets, cutout boxes, fittings, boxes, and panelboard enclosures. Cabinets, cutout boxes,
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fittings, boxes, and panelboard enclosures in
damp or wet locations shall be installed so as
to prevent moisture or water from entering
and accumulating within the enclosures and
shall be mounted so there is at least 6.35-mm
(0.25-in.) airspace between the enclosure and
the wall or other supporting surface. However, nonmetallic enclosures may be installed without the airspace on a concrete,
masonry, tile, or similar surface. The enclosures shall be weatherproof in wet locations.
(2) Switches, circuit breakers, and switchboards. Switches, circuit breakers, and
switchboards installed in wet locations shall
be enclosed in weatherproof enclosures.
(f) Conductors for general wiring—(1) Insulation. All conductors used for general wiring
shall be insulated unless otherwise permitted
in this subpart.
(2) Type. The conductor insulation shall be
of a type that is approved for the voltage, operating temperature, and location of use.
(3) Distinguishable. Insulated conductors
shall be distinguishable by appropriate color
or other suitable means as being grounded
conductors, ungrounded conductors, or
equipment grounding conductors.
(g) Flexible cords and cables—(1)Use of flexible cords and cables. (i) Flexible cords and cables shall be approved for conditions of use
and location.
(ii) Flexible cords and cables may be used
only for:
(A) Pendants;
(B) Wiring of fixtures;
(C) Connection of portable lamps or appliances;
(D) Portable and mobile signs;
(E) Elevator cables;
(F) Wiring of cranes and hoists;
(G) Connection of stationary equipment to
facilitate their frequent interchange;
(H) Prevention of the transmission of noise
or vibration;
(I) Appliances where the fastening means
and mechanical connections are designed to
permit removal for maintenance and repair;
(J) Data processing cables approved as a
part of the data processing system;
(K) Connection of moving parts; and
(L) Temporary wiring as permitted in paragraph (a)(2) of this section.
(iii) If used as permitted in paragraphs
(g)(1)(ii)(C), (g)(1)(ii)(G), or (g)(1)(ii)(I) of this
section, the flexible cord shall be equipped
with an attachment plug and shall be energized from an approved receptacle outlet.
(iv) Unless specifically permitted otherwise in paragraph (g)(1)(ii) of this section,
flexible cords and cables may not be used:
(A) As a substitute for the fixed wiring of
a structure;
(B) Where run through holes in walls, ceilings, or floors;
(C) Where run through doorways, windows,
or similar openings;
(D) Where attached to building surfaces;
§ 1910.305
(E) Where concealed behind building walls,
ceilings, or floors; or
(F) Where installed in raceways, except as
otherwise permitted in this subpart.
(v) Flexible cords used in show windows
and showcases shall be Type S, SE, SEO,
SEOO, SJ, SJE, SJEO, SJEOO, SJO, SJOO,
SJT, SJTO, SJTOO, SO, SOO, ST, STO, or
STOO, except for the wiring of chain-supported lighting fixtures and supply cords for
portable lamps and other merchandise being
displayed or exhibited.
(2) Identification, splices, and terminations.
(i) A conductor of a flexible cord or cable
that is used as a grounded conductor or an
equipment grounding conductor shall be distinguishable from other conductors. Types S,
SC, SCE, SCT, SE, SEO, SEOO, SJ, SJE,
SJEO, SJEOO, SJO, SJT, SJTO, SJTOO, SO,
SOO, ST, STO, and STOO flexible cords and
Types G, G–GC, PPE, and W flexible cables
shall be durably marked on the surface at intervals not exceeding 610 mm (24 in.) with
the type designation, size, and number of
conductors.
(ii) Flexible cords may be used only in continuous lengths without splice or tap. Hardservice cord and junior hard-service cord No.
14 and larger may be repaired if spliced so
that the splice retains the insulation, outer
sheath properties, and usage characteristics
of the cord being spliced.
(iii) Flexible cords and cables shall be connected to devices and fittings so that strain
relief is provided that will prevent pull from
being directly transmitted to joints or terminal screws.
(h) Portable cables over 600 volts, nominal.
This paragraph applies to portable cables
used at more than 600 volts, nominal.
(1) Conductor construction. Multiconductor
portable cable for use in supplying power to
portable or mobile equipment at over 600
volts, nominal, shall consist of No. 8 or larger conductors employing flexible stranding.
However, the minimum size of the insulated
ground-check conductor of Type G–GC cables
shall be No. 10.
(2) Shielding. Cables operated at over 2,000
volts shall be shielded for the purpose of confining the voltage stresses to the insulation.
(3) Equipment grounding conductors. Grounding conductors shall be provided.
(4) Grounding shields. All shields shall be
grounded.
(5) Minimum bending radii. The minimum
bending radii for portable cables during installation and handling in service shall be
adequate to prevent damage to the cable.
(6) Fittings. Connectors used to connect
lengths of cable in a run shall be of a type
that lock firmly together. Provisions shall
be made to prevent opening or closing these
connectors while energized. Strain relief
shall be provided at connections and terminations.
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§ 1910.305
29 CFR Ch. XVII (7–1–07 Edition)
(7) Splices. Portable cables may not be operated with splices unless the splices are of
the permanent molded, vulcanized, or other
approved type.
(8) Terminations. Termination enclosures
shall be suitably marked with a high voltage
hazard warning, and terminations shall be
accessible only to authorized and qualified
employees.
(i) Fixture wires—(1) General. Fixture wires
shall be approved for the voltage, temperature, and location of use. A fixture wire
which is used as a grounded conductor shall
be identified.
(2) Uses permitted. Fixture wires may be
used only:
(i) For installation in lighting fixtures and
in similar equipment where enclosed or protected and not subject to bending or twisting
in use; or
(ii) For connecting lighting fixtures to the
branch-circuit conductors supplying the fixtures.
(3) Uses not permitted. Fixture wires may
not be used as branch-circuit conductors except as permitted for Class 1 power limited
circuits and for fire alarm circuits.
(j) Equipment for general use—(1) Lighting
fixtures, lampholders, lamps, and receptacles. (i)
Fixtures, lampholders, lamps, rosettes, and
receptacles may have no live parts normally
exposed to employee contact. However, rosettes and cleat-type lampholders and receptacles located at least 2.44 m (8.0 ft) above
the floor may have exposed terminals.
(ii) Handlamps of the portable type supplied through flexible cords shall be equipped
with a handle of molded composition or
other material identified for the purpose,
and a substantial guard shall be attached to
the lampholder or the handle. Metal shell,
paper-lined lampholders may not be used.
(iii) Lampholders of the screw-shell type
shall be installed for use as lampholders
only. Where supplied by a circuit having a
grounded conductor, the grounded conductor
shall be connected to the screw shell.
Lampholders installed in wet or damp locations shall be of the weatherproof type.
(iv) Fixtures installed in wet or damp locations shall be identified for the purpose and
shall be so constructed or installed that
water cannot enter or accumulate in
wireways, lampholders, or other electrical
parts.
(2) Receptacles, cord connectors, and attachment plugs (caps). (i) All 15- and 20-ampere attachment plugs and connectors shall be constructed so that there are no exposed current-carrying parts except the prongs,
blades, or pins. The cover for wire terminations shall be a part that is essential for
the operation of an attachment plug or connector (dead-front construction). Attachment plugs shall be installed so that their
prongs, blades, or pins are not energized unless inserted into an energized receptacle. No
receptacles may be installed so as to require
an energized attachment plug as its source of
supply.
(ii) Receptacles, cord connectors, and attachment plugs shall be constructed so that
no receptacle or cord connector will accept
an attachment plug with a different voltage
or current rating than that for which the device is intended. However, a 20-ampere T-slot
receptacle or cord connector may accept a
15-ampere attachment plug of the same voltage rating.
(iii) Nongrounding-type receptacles and
connectors may not be used for groundingtype attachment plugs.
(iv) A receptacle installed in a wet or damp
location shall be suitable for the location.
(v) A receptacle installed outdoors in a location protected from the weather or in
other damp locations shall have an enclosure
for the receptacle that is weatherproof when
the receptacle is covered (attachment plug
cap not inserted and receptacle covers
closed).
NOTE TO PARAGRAPH (J)(2)(V) OF THIS SECTION. A receptacle is considered to be in a location protected from the weather when it is
located under roofed open porches, canopies,
marquees, or the like and where it will not
be subjected to a beating rain or water runoff.
(vi) A receptacle installed in a wet location
where the product intended to be plugged
into it is not attended while in use (for example, sprinkler system controllers, landscape lighting, and holiday lights) shall have
an enclosure that is weatherproof with the
attachment plug cap inserted or removed.
(vii) A receptacle installed in a wet location where the product intended to be
plugged into it will be attended while in use
(for example, portable tools) shall have an
enclosure that is weatherproof when the attachment plug cap is removed.
(3) Appliances. (i) Appliances may have no
live parts normally exposed to contact other
than parts functioning as open-resistance
heating elements, such as the heating elements of a toaster, which are necessarily exposed.
(ii) Each appliance shall have a means to
disconnect it from all ungrounded conductors. If an appliance is supplied by more than
one source, the disconnecting means shall be
grouped and identified.
(iii) Each electric appliance shall be provided with a nameplate giving the identifying name and the rating in volts and amperes, or in volts and watts. If the appliance
is to be used on a specific frequency or frequencies, it shall be so marked. Where motor
overload protection external to the appliance is required, the appliance shall be so
marked.
(iv) Marking shall be located so as to be
visible or easily accessible after installation.
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(4) Motors. This paragraph applies to motors, motor circuits, and controllers.
(i) If specified in paragraph (j)(4) of this
section that one piece of equipment shall be
‘‘within sight of’’ another piece of equipment, the piece of equipment shall be visible
and not more than 15.24 m (50.0 ft) from the
other.
(ii) An individual disconnecting means
shall be provided for each controller. A disconnecting means shall be located within
sight of the controller location. However, a
single disconnecting means may be located
adjacent to a group of coordinated controllers mounted adjacent to each other on a
multi-motor continuous process machine.
The controller disconnecting means for
motor branch circuits over 600 volts, nominal, may be out of sight of the controller, if
the controller is marked with a warning
label giving the location and identification
of the disconnecting means that is to be
locked in the open position.
(iii) The disconnecting means shall disconnect the motor and the controller from
all ungrounded supply conductors and shall
be so designed that no pole can be operated
independently.
(iv) The disconnecting means shall plainly
indicate whether it is in the open (off) or
closed (on) position.
(v) The disconnecting means shall be readily accessible. If more than one disconnect is
provided for the same equipment, only one
need be readily accessible.
(vi) An individual disconnecting means
shall be provided for each motor, but a single
disconnecting means may be used for a group
of motors under any one of the following
conditions:
(A) If a number of motors drive several
parts of a single machine or piece of apparatus, such as a metal or woodworking machine, crane, or hoist;
(B) If a group of motors is under the protection of one set of branch-circuit protective devices; or
(C) If a group of motors is in a single room
within sight of the location of the disconnecting means.
(vii) Motors, motor-control apparatus, and
motor branch-circuit conductors shall be
protected against overheating due to motor
overloads or failure to start, and against
short-circuits or ground faults. These provisions do not require overload protection that
will stop a motor where a shutdown is likely
to introduce additional or increased hazards,
as in the case of fire pumps, or where continued operation of a motor is necessary for a
safe shutdown of equipment or process and
motor overload sensing devices are connected to a supervised alarm.
(viii) Where live parts of motors or controllers operating at over 150 volts to ground
are guarded against accidental contact only
by location, and where adjustment or other
§ 1910.305
attendance may be necessary during the operation of the apparatus, suitable insulating
mats or platforms shall be provided so that
the attendant cannot readily touch live
parts unless standing on the mats or platforms.
(5) Transformers. (i) Paragraph (j)(5) of this
section covers the installation of all transformers except the following:
(A) Current transformers;
(B) Dry-type transformers installed as a
component part of other apparatus;
(C) Transformers that are an integral part
of an X-ray, high frequency, or electrostaticcoating apparatus;
(D) Transformers used with Class 2 and
Class 3 circuits, sign and outline lighting,
electric discharge lighting, and power-limited fire-alarm circuits; and
(E) Liquid-filled or dry-type transformers
used for research, development, or testing,
where effective safeguard arrangements are
provided.
(ii) The operating voltage of exposed live
parts of transformer installations shall be
indicated by signs or visible markings on the
equipment or structure.
(iii) Dry-type, high fire point liquid-insulated, and askarel-insulated transformers installed indoors and rated over 35kV shall be
in a vault.
(iv) Oil-insulated transformers installed indoors shall be installed in a vault.
(v) Combustible material, combustible
buildings and parts of buildings, fire escapes,
and door and window openings shall be safeguarded from fires that may originate in oilinsulated transformers attached to or adjacent to a building or combustible material.
(vi) Transformer vaults shall be constructed so as to contain fire and combustible liquids within the vault and to prevent
unauthorized access. Locks and latches shall
be so arranged that a vault door can be readily opened from the inside.
(vii) Any pipe or duct system foreign to the
electrical installation may not enter or pass
through a transformer vault.
NOTE TO PARAGRAPH (J)(5)(VII) OF THIS SECTION. Piping or other facilities provided for
vault fire protection, or for transformer
cooling, are not considered foreign to the
electrical installation.
(viii) Material may not be stored in transformer vaults.
(6) Capacitors. (i) All capacitors, except
surge capacitors or capacitors included as a
component part of other apparatus, shall be
provided with an automatic means of draining the stored charge after the capacitor is
disconnected from its source of supply.
(ii) The following requirements apply to
capacitors installed on circuits operating at
more than 600 volts, nominal:
(A) Group-operated switches shall be used
for capacitor switching and shall be capable
of the following:
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§ 1910.306
29 CFR Ch. XVII (7–1–07 Edition)
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(1) Carrying continuously not less than 135
percent of the rated current of the capacitor
installation;
(2) Interrupting the maximum continuous
load current of each capacitor, capacitor
bank, or capacitor installation that will be
switched as a unit;
(3) Withstanding the maximum inrush current, including contributions from adjacent
capacitor installations; and
(4) Carrying currents due to faults on the
capacitor side of the switch;
(B) A means shall be installed to isolate
from all sources of voltage each capacitor,
capacitor bank, or capacitor installation
that will be removed from service as a unit.
The isolating means shall provide a visible
gap in the electric circuit adequate for the
operating voltage;
(C) Isolating or disconnecting switches
(with no interrupting rating) shall be
interlocked with the load interrupting device or shall be provided with prominently
displayed caution signs to prevent switching
load current; and
(D) For series capacitors, the proper
switching shall be assured by use of at least
one of the following:
(1) Mechanically sequenced isolating and
bypass switches;
(2) Interlocks; or
(3) Switching procedure prominently displayed at the switching location.
(7) Storage Batteries. Provisions shall be
made for sufficient diffusion and ventilation
of gases from storage batteries to prevent
the accumulation of explosive mixtures.
§ 1910.306 Specific purpose equipment
and installations.
(a) Electric signs and outline lighting—
(1) Disconnecting means. Signs operated
by electronic or electromechanical
controllers located outside the sign
shall have a disconnecting means located inside the controller enclosure or
within sight of the controller location,
and it shall be capable of being locked
in the open position. Such disconnecting means shall have no pole
that can be operated independently,
and it shall open all ungrounded conductors that supply the controller and
sign. All other signs, except the portable type, and all outline lighting installations shall have an externally operable disconnecting means which can
open all ungrounded conductors and is
within the sight of the sign or outline
lighting it controls.
(2) Doors or covers giving access to
uninsulated parts of indoor signs or
outline lighting exceeding 600 volts and
accessible to other than qualified persons shall either be provided with
interlock switches to disconnect the
primary circuit or shall be so fastened
that the use of other than ordinary
tools will be necessary to open them.
(b) Cranes and hoists. This paragraph
applies to the installation of electric
equipment and wiring used in connection with cranes, monorail hoists,
hoists, and all runways.
(1) Disconnecting means. A readily accessible disconnecting means (i) shall
be provided between the runway contact conductors and the power supply.
(ii) Another disconnecting means, capable of being locked in the open position, shall be provided in the leads
from the runway contact conductors or
other power supply on any crane or
monorail hoist.
(A) If this additional disconnecting
means is not readily accessible from
the crane or monorail hoist operating
station, means shall be provided at the
operating station to open the power
circuit to all motors of the crane or
monorail hoist.
(B) The additional disconnect may be
omitted if a monorail hoist or handpropelled crane bridge installation
meets all of the following:
(1) The unit is floor controlled;
(2) The unit is within view of the
power supply disconnecting means; and
(3) No fixed work platform has been
provided for servicing the unit.
(2) Control. A limit switch or other
device shall be provided to prevent the
load block from passing the safe upper
limit of travel of any hoisting mechanism.
(3) Clearance. The dimension of the
working space in the direction of access to live parts which may require
examination, adjustment, servicing, or
maintenance while alive shall be a
minimum of 2 feet 6 inches. Where controls are enclosed in cabinets, the
door(s) shall either open at least 90 degrees or be removable.
(c) Elevators, dumbwaiters, escalators,
and moving walks—(1) Disconnecting
means. Elevators, dumbwaiters, escalators, and moving walks shall have a
single means for disconnecting all
ungrounded main power supply conductors for each unit.
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§ 1910.307
29 CFR Ch. XVII (7–1–07 Edition)
(i) Boxes shall be designed so that no live
parts are exposed to accidental contact.
Where installed outdoors, the box shall be of
weatherproof construction and mounted so
that the bottom of the enclosure is not less
than 152 mm (6 in.) above the ground;
(ii) Busbars shall have an ampere rating
not less than the overcurrent device supplying the feeder supplying the box. Busbar
connectors shall be provided where conductors terminate directly on busbars;
(iii) Receptacles shall have overcurrent
protection installed within the box. The
overcurrent protection may not exceed the
ampere rating of the receptacle, except as
permitted in § 1910.305(j)(4) for motor loads;
(iv) Where single-pole connectors are used,
they shall comply with the following:
(A) Where ac single-pole portable cable
connectors are used, they shall be listed and
of the locking type. Where paralleled sets of
current-carrying single-pole separable connectors are provided as input devices, they
shall be prominently labeled with a warning
indicating the presence of internal parallel
connections. The use of single-pole separable
connectors shall comply with at least one of
the following conditions:
(1) Connection and disconnection of connectors are only possible where the supply
connectors are interlocked to the source and
it is not possible to connect or disconnect
connectors when the supply is energized; or
(2) Line connectors are of the listed sequential-interlocking type so that load connectors are connected in the following sequence:
(i) Equipment grounding conductor connection;
(ii) Grounded circuit-conductor connection,
if provided; and
(iii) Ungrounded conductor connection; and
so that disconnection is in the reverse order;
or
(3) A caution notice is provided adjacent to
the line connectors indicating that plug connection must be in the following sequence:
(i) Equipment grounding conductor connection;
(ii) Grounded circuit-conductor connection,
if provided; and
(iii) Ungrounded conductor connection; and
indicating that disconnection is in the reverse order; and
(B) Single-pole separable connectors used
in portable professional motion picture and
television equipment may be interchangeable for ac or dc use or for different current
ratings on the same premises only if they are
listed for ac/dc use and marked to identify
the system to which they are connected;
(v) Overcurrent protection of equipment
and conductors shall be provided; and
(vi) The following equipment connected to
the same source shall be bonded:
(A) Metal raceways and metal sheathed
cable;
(B) Metal enclosures of electrical equipment; and
(C) Metal frames and metal parts of rides,
concessions, trailers, trucks, or other equipment that contain or support electrical
equipment.
(5) Disconnecting means. (i) Each ride and
concession shall be provided with a fused disconnect switch or circuit breaker located
within sight and within 1.83 m (6 ft) of the
operator’s station.
(ii) The disconnecting means shall be readily accessible to the operator, including
when the ride is in operation.
(iii) Where accessible to unqualified persons, the enclosure for the switch or circuit
breaker shall be of the lockable type.
(iv) A shunt trip device that opens the
fused disconnect or circuit breaker when a
switch located in the ride operator’s console
is closed is a permissible method of opening
the circuit.
§ 1910.307
tions.
Hazardous (classified) loca-
(a) Scope. This section covers the requirements for electric equipment and
wiring in locations which are classified
depending on the properties of the
flammable vapors, liquids or gases, or
combustible dusts or fibers which may
be present therein and the likelihood
that a flammable or combustible concentration or quantity is present. Hazardous (classified) locations may be
found in occupancies such as, but not
limited to, the following: aircraft
hangars, gasoline dispensing and service stations, bulk storage plants for
gasoline or other volatile flammable
liquids, paint-finishing process plants,
health care facilities, agricultural or
other facilities where excessive combustible dusts may be present, marinas, boat yards, and petroleum and
chemical processing plants. Each room,
section or area shall be considered individually in determining its classification. These hazardous (classified) locations are assigned six designations as
follows:
Class
Class
Class
Class
Class
Class
I, Division 1
I, Division 2
II, Division 1
II, Division 2
III, Division 1
III, Division 2
For definitions of these locations see
§ 1910.399(a). All applicable requirements in this subpart shall apply to
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Occupational Safety and Health Admin., Labor
hazardous (classified) locations, unless
modified by provisions of this section.
(b) Electrical installations. Equipment,
wiring methods, and installations of
equipment in hazardous (classified) locations shall be intrinsically safe, approved for the hazardous (classified) location, or safe or for the hazardous
(classified) location. Requirements for
each of these options are as follows:
(1) Intrinsically safe. Equipment and
associated wiring approved as intrinsically safe shall be permitted in any
hazardous (classified) location for
which it is approved.
(2) Approved for the hazardous (classified) location. (i) Equipment shall be approved not only for the class of location but also for the ignitible or combustible properties of the specific gas,
vapor, dust, or fiber that will be
present.
rfrederick on PROD1PC67 with CFR
NOTE: NFPA 70, the National Electrical
Code, lists or defines hazardous gases, vapors, and dusts by ‘‘Groups’’ characterized by
their ignitible or combustible properties.
(ii) Equipment shall be marked to
show the class, group, and operating
temperature or temperature range,
based on operation in a 40 degrees C
ambient, for which it is approved. The
temperature marking may not exceed
the ignition temperature of the specific
gas or vapor to be encountered. However, the following provisions modify
this marking requirement for specific
equipment:
(A) Equipment of the non-heat-producing type, such as junction boxes,
conduit, and fittings, and equipment of
the heat-producing type having a maximum temperature not more than 100
degrees C (212 degrees F) need not have
a marked operating temperature or
temperature range.
(B) Fixed lighting fixtures marked
for use in Class I, Division 2 locations
only, need not be marked to indicate
the group.
(C) Fixed general-purpose equipment
in Class I locations, other than lighting
fixtures, which is acceptable for use in
Class I, Division 2 locations need not be
marked with the class, group, division,
or operating temperature.
(D) Fixed dust-tight equipment,
other than lighting fixtures, which is
acceptable for use in Class II, Division
2 and Class III locations need not be
§ 1910.307
marked with the class, group, division,
or operating temperature.
(3) Safe for the hazardous (classified)
location. Equipment which is safe for
the location shall be of a type and design which the employer demonstrates
will provide protection from the hazards arising from the combustibility
and flammability of vapors, liquids,
gases, dusts, or fibers.
NOTE: The National Electrical Code, NFPA
70, contains guidelines for determining the
type and design of equipment and installations which will meet this requirement. The
guidelines of this document address electric
wiring, equipment, and systems installed in
hazardous (classified) locations and contain
specific provisions for the following: wiring
methods, wiring connections; conductor insulation, flexible cords, sealing and drainage,
transformers, capacitors, switches, circuit
breakers, fuses, motor controllers, receptacles, attachment plugs, meters, relays, instruments, resistors, generators, motors,
lighting fixtures, storage battery charging
equipment, electric cranes, electric hoists
and similar equipment, utilization equipment, signaling systems, alarm systems, remote control systems, local loud speaker and
communication systems, ventilation piping,
live parts, lightning surge protection, and
grounding. Compliance with these guidelines
will constitute one means, but not the only
means, of compliance with this paragraph.
(c) Conduits. All conduits shall be
threaded and shall be made wrenchtight. Where it is impractical to make
a threaded joint tight, a bonding jumper shall be utilized.
(d) Equipment in Division 2 locations.
Equipment that has been approved for
a Division 1 location may be installed
in a Division 2 location of the same
class and group. General-purpose equipment or equipment in general-purpose
enclosures may be installed in Division
2 locations if the equipment does not
constitute a source of ignition under
normal operating conditions.
[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7,
1981]
EFFECTIVE DATE NOTE: At 72 FR 7210, Feb.
14, 2007, § 1910.307 was revised, effective Aug.
13, 2007. For the convenience of the user, the
revised text is set forth as follows:
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§ 1910.307
29 CFR Ch. XVII (7–1–07 Edition)
§ 1910.307 Hazardous (classified) locations.
(a) Scope—(1) Applicability. This section
covers the requirements for electric equipment and wiring in locations that are classified depending on the properties of the flammable vapors, liquids or gases, or combustible dusts or fibers that may be present
therein and the likelihood that a flammable
or combustible concentration or quantity is
present. Hazardous (classified) locations may
be found in occupancies such as, but not limited to, the following: aircraft hangars, gasoline dispensing and service stations, bulk
storage plants for gasoline or other volatile
flammable liquids, paint-finishing process
plants, health care facilities, agricultural or
other facilities where excessive combustible
dusts may be present, marinas, boat yards,
and petroleum and chemical processing
plants. Each room, section or area shall be
considered individually in determining its
classification.
(2) Classifications. (i) These hazardous (classified) locations are assigned the following
designations:
(A) Class I, Division 1
(B) Class I, Division 2
(C) Class I, Zone 0
(D) Class I, Zone 1
(E) Class I, Zone 2
(F) Class II, Division 1
(G) Class II, Division 2
(H) Class III, Division 1
(I) Class III, Division 2
(ii) For definitions of these locations, see
§ 1910.399.
(3) Other sections of this subpart. All applicable requirements in this subpart apply to
hazardous (classified) locations unless modified by provisions of this section.
(4) Division and zone classification. In Class
I locations, an installation must be classified
as using the division classification system
meeting paragraphs (c), (d), (e), and (f) of
this section or using the zone classification
system meeting paragraph (g) of this section.
In Class II and Class III locations, an installation must be classified using the division
classification system meeting paragraphs
(c), (d), (e), and (f) of this section.
(b) Documentation. All areas designated as
hazardous (classified) locations under the
Class and Zone system and areas designated
under the Class and Division system established after August 13, 2007 shall be properly
documented. This documentation shall be
available to those authorized to design, install, inspect, maintain, or operate electric
equipment at the location.
(c) Electrical installations. Equipment, wiring methods, and installations of equipment
in hazardous (classified) locations shall be
intrinsically safe, approved for the hazardous
(classified) location, or safe for the hazardous (classified) location. Requirements
for each of these options are as follows:
(1) Intrinsically safe. Equipment and associated wiring approved as intrinsically safe is
permitted in any hazardous (classified) location for which it is approved;
(2) Approved for the hazardous (classified) location. (i) Equipment shall be approved not
only for the class of location, but also for the
ignitable or combustible properties of the
specific gas, vapor, dust, or fiber that will be
present.
NOTE TO PARAGRAPH (C)(2)(I) OF THIS SECTION: NFPA 70, the National Electrical Code,
lists or defines hazardous gases, vapors, and
dusts by ‘‘Groups’’ characterized by their ignitable or combustible properties.
(ii) Equipment shall be marked to show the
class, group, and operating temperature or
temperature range, based on operation in a
40-degree C ambient, for which it is approved. The temperature marking may not
exceed the ignition temperature of the specific gas or vapor to be encountered. However, the following provisions modify this
marking requirement for specific equipment:
(A) Equipment of the nonheat-producing
type, such as junction boxes, conduit, and
fittings, and equipment of the heat-producing type having a maximum temperature
not more than 100 °C (212 °F) need not have
a marked operating temperature or temperature range;
(B) Fixed lighting fixtures marked for use
in Class I, Division 2 or Class II, Division 2
locations only need not be marked to indicate the group;
(C) Fixed general-purpose equipment in
Class I locations, other than lighting fixtures, that is acceptable for use in Class I,
Division 2 locations need not be marked with
the class, group, division, or operating temperature;
(D) Fixed dust-tight equipment, other than
lighting fixtures, that is acceptable for use
in Class II, Division 2 and Class III locations
need not be marked with the class, group, division, or operating temperature; and
(E) Electric equipment suitable for ambient temperatures exceeding 40 °C (104 °F)
shall be marked with both the maximum ambient temperature and the operating temperature or temperature range at that ambient temperature; and
(3) Safe for the hazardous (classified) location. Equipment that is safe for the location
shall be of a type and design that the employer demonstrates will provide protection
from the hazards arising from the combustibility and flammability of vapors, liquids,
gases, dusts, or fibers involved.
NOTE TO PARAGRAPH (C)(3) OF THIS SECTION:
The National Electrical Code, NFPA 70, contains guidelines for determining the type and
design of equipment and installations that
will meet this requirement. Those guidelines
address electric wiring, equipment, and systems installed in hazardous (classified) locations and contain specific provisions for the
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Occupational Safety and Health Admin., Labor
following: wiring methods, wiring connections; conductor insulation, flexible cords,
sealing and drainage, transformers, capacitors, switches, circuit breakers, fuses, motor
controllers, receptacles, attachment plugs,
meters, relays, instruments, resistors, generators, motors, lighting fixtures, storage
battery charging equipment, electric cranes,
electric hoists and similar equipment, utilization equipment, signaling systems, alarm
systems, remote control systems, local loud
speaker and communication systems, ventilation piping, live parts, lightning surge
protection, and grounding.
(d) Conduits. All conduits shall be threaded
and shall be made wrench-tight. Where it is
impractical to make a threaded joint tight, a
bonding jumper shall be utilized.
(e) Equipment in Division 2 locations. Equipment that has been approved for a Division 1
location may be installed in a Division 2 location of the same class and group. Generalpurpose equipment or equipment in generalpurpose enclosures may be installed in Division 2 locations if the employer can demonstrate that the equipment does not constitute a source of ignition under normal operating conditions.
(f) Protection techniques. The following are
acceptable protection techniques for electric
and electronic equipment in hazardous (classified) locations.
(1) Explosionproof apparatus. This protection technique is permitted for equipment in
the Class I, Division 1 and 2 locations for
which it is approved.
(2) Dust ignitionproof. This protection technique is permitted for equipment in the Class
II, Division 1 and 2 locations for which it is
approved.
(3) Dust-tight. This protection technique is
permitted for equipment in the Class II, Division 2 and Class III locations for which it
is approved.
(4) Purged and pressurized. This protection
technique is permitted for equipment in any
hazardous (classified) location for which it is
approved.
(5) Nonincendive circuit. This protection
technique is permitted for equipment in
Class I, Division 2; Class II, Division 2; or
Class III, Division 1or 2 locations.
(6) Nonincendive equipment. This protection
technique is permitted for equipment in
Class I, Division 2; Class II, Division 2; or
Class III, Division 1 or 2 locations.
(7) Nonincendive component. This protection
technique is permitted for equipment in
Class I, Division 2; Class II, Division 2; or
Class III, Division 1 or 2 locations.
(8) Oil immersion. This protection technique
is permitted for current-interrupting contacts in Class I, Division 2 locations as described in the Subpart.
(9) Hermetically sealed. This protection
technique is permitted for equipment in
§ 1910.307
Class I, Division 2; Class II, Division 2; and
Class III, Division 1 or 2 locations.
(10) Other protection techniques. Any other
protection technique that meets paragraph
(c) of this section is acceptable in any hazardous (classified) location.
(g) Class I, Zone 0, 1, and 2 locations—(1)
Scope. Employers may use the zone classification system as an alternative to the division classification system for electric and
electronic equipment and wiring for all voltage in Class I, Zone 0, Zone 1, and Zone 2 hazardous (classified) locations where fire or explosion hazards may exist due to flammable
gases, vapors, or liquids.
(2) Location and general requirements. (i) Locations shall be classified depending on the
properties of the flammable vapors, liquids,
or gases that may be present and the likelihood that a flammable or combustible concentration or quantity is present. Where
pyrophoric materials are the only materials
used or handled, these locations need not be
classified.
(ii) Each room, section, or area shall be
considered individually in determining its
classification.
(iii) All threaded conduit shall be threaded
with an NPT (National (American) Standard
Pipe Taper) standard conduit cutting die
that provides 3⁄4-in. taper per foot. The conduit shall be made wrench tight to prevent
sparking when fault current flows through
the conduit system and to ensure the
explosionproof or flameproof integrity of the
conduit system where applicable.
(iv) Equipment provided with threaded entries for field wiring connection shall be installed in accordance with paragraph
(g)(2)(iv)(A) or (g)(2)(iv)(B) of this section.
(A) For equipment provided with threaded
entries for NPT threaded conduit or fittings,
listed conduit, conduit fittings, or cable fittings shall be used.
(B) For equipment with metric threaded
entries, such entries shall be identified as
being metric, or listed adaptors to permit
connection to conduit of NPT-threaded fittings shall be provided with the equipment.
Adapters shall be used for connection to conduit or NPT-threaded fittings.
(3) Protection techniques. One or more of the
following protection techniques shall be used
for electric and electronic equipment in hazardous (classified) locations classified under
the zone classification system.
(i) Flameproof ‘‘d’’—This protection technique is permitted for equipment in the Class
I, Zone 1 locations for which it is approved.
(ii) Purged and pressurized—This protection technique is permitted for equipment in
the Class I, Zone 1 or Zone 2 locations for
which it is approved.
(iii) Intrinsic safety—This protection technique is permitted for equipment in the Class
I, Zone 0 or Zone 1 locations for which it is
approved.
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§ 1910.307
29 CFR Ch. XVII (7–1–07 Edition)
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(iv) Type of protection ‘‘n’’—This protection technique is permitted for equipment in
the Class I, Zone 2 locations for which it is
approved. Type of protection ‘‘n’’ is further
subdivided into nA, nC, and nR.
(v) Oil Immersion ‘‘o’’—This protection
technique is permitted for equipment in the
Class I, Zone 1 locations for which it is approved.
(vi) Increased safety ‘‘e’’—This protection
technique is permitted for equipment in the
Class I, Zone 1 locations for which it is approved.
(vii) Encapsulation ‘‘m’’—This protection
technique is permitted for equipment in the
Class I, Zone 1 locations for which it is approved.
(viii) Powder Filling ‘‘q’’—This protection
technique is permitted for equipment in the
Class I, Zone 1 locations for which it is approved.
(4) Special precaution. Paragraph (g) of this
section requires equipment construction and
installation that will ensure safe performance under conditions of proper use and
maintenance.
(i) Classification of areas and selection of
equipment and wiring methods shall be
under the supervision of a qualified registered professional engineer.
(ii) In instances of areas within the same
facility classified separately, Class I, Zone 2
locations may abut, but not overlap, Class I,
Division 2 locations. Class I, Zone 0 or Zone
1 locations may not abut Class I, Division 1
or Division 2 locations.
(iii) A Class I, Division 1 or Division 2 location may be reclassified as a Class I, Zone 0,
Zone 1, or Zone 2 location only if all of the
space that is classified because of a single
flammable gas or vapor source is reclassified.
NOTE TO PARAGRAPH (G)(4) OF THIS SECTION:
Low ambient conditions require special consideration. Electric equipment depending on
the protection techniques described by paragraph (g)(3)(i) of this section may not be
suitable for use at temperatures lower than
¥20 °C (¥4 °F) unless they are approved for
use at lower temperatures. However, at low
ambient temperatures, flammable concentrations of vapors may not exist in a lo-
cation classified Class I, Zone 0, 1, or 2 at
normal ambient temperature.
(5) Listing and marking. (i) Equipment that
is listed for a Zone 0 location may be installed in a Zone 1 or Zone 2 location of the
same gas or vapor. Equipment that is listed
for a Zone 1 location may be installed in a
Zone 2 location of the same gas or vapor.
(ii) Equipment shall be marked in accordance
with
paragraph
(g)(5)(ii)(A)
and
(g)(5)(ii)(B) of this section, except as provided in (g)(5)(ii)(C).
(A) Equipment approved for Class I, Division 1 or Class 1, Division 2 shall, in addition
to being marked in accordance with (c)(2)(ii),
be marked with the following:
(1) Class I, Zone 1 or Class I, Zone 2 (as applicable);
(2) Applicable gas classification groups;
and
(3) Temperature classification; or
(B) Equipment meeting one or more of the
protection techniques described in paragraph
(g)(3) of this section shall be marked with
the following in the order shown:
(1) Class, except for intrinsically safe apparatus;
(2) Zone, except for intrinsically safe apparatus;
(3) Symbol ‘‘AEx;’’
(4) Protection techniques;
(5) Applicable gas classification groups;
and
(6) Temperature classification, except for
intrinsically safe apparatus.
NOTE TO PARAGRAPH (G)(5)(II)(B) OF THIS
SECTION: An example of such a required
marking is ‘‘Class I, Zone 0, AEx ia IIC T6.’’
See Figure S–1 for an explanation of this
marking.
(C) Equipment that the employer demonstrates will provide protection from the
hazards arising from the flammability of the
gas or vapor and the zone of location involved and will be recognized as providing
such protection by employees need not be
marked.
NOTE TO PARAGRAPH (g)(5)(ii)(C) OF THIS
SECTION: The National Electrical Code,
NFPA 70, contains guidelines for determining the type and design of equipment and
installations that will meet this provision.
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§ 1910.308 Special systems.
(a) Systems over 600 volts, nominal.
Paragraphs (a) (1) through (4) of this
section cover the general requirements
for all circuits and equipment operated
at over 600 volts.
(1) Wiring methods for fixed installations. (i) Above-ground conductors shall
be installed in rigid metal conduit, in
intermediate metal conduit, in cable
trays, in cablebus, in other suitable
raceways, or as open runs of metal-clad
cable suitable for the use and purpose.
However, open runs of non-metallicsheathed cable or of bare conductors or
busbars may be installed in locations
accessible only to qualified persons.
Metallic shielding components, such as
tapes, wires, or braids for conductors,
shall be grounded. Open runs of insulated wires and cables having a bare
lead sheath or a braided outer covering
shall be supported in a manner designed to prevent physical damage to
the braid or sheath.
(ii) Conductors emerging from the
ground shall be enclosed in approved
raceways. (See § 1910.302(b)(3).)
(2) Interrupting and isolating devices.
(i) Circuit breaker installations located
indoors shall consist of metal-enclosed
units or fire-resistant cell-mounted
units. In locations accessible only to
qualified personnel, open mounting of
circuit breakers is permitted. A means
of indicating the open and closed position of circuit breakers shall be provided.
(ii) Fused cutouts installed in buildings or tranformer vaults shall be of a
type approved for the purpose. They
§ 1910.308
shall be readily accessible for fuse replacement.
(iii) A means shall be provided to
completely isolate equipment for inspection and repairs. Isolating means
which are not designed to interrupt the
load curent of the circuit shall be either interlocked with an approved circuit interrupter or provided with a sign
warning against opening them under
load.
(3) Mobile and portable equipment. (i)
Power cable connections to mobile machines. A metallic enclosure shall be
provided on the mobile machine for enclosing the terminals of the power
cable. The enclosure shall include provisions for a solid connection for the
ground wire(s) terminal to effectively
ground the machine frame. The method
of cable termination used shall prevent
any strain or pull on the cable from
stressing the electrical connections.
The enclosure shall have provision for
locking so only authorized qualified
persons may open it and shall be
marked with a sign warning of the
presence of energized parts.
(ii) Guarding live parts. All energized
switching and control parts shall be enclosed in effectively grounded metal
cabinets or enclosures. Circuit breakers and protective equipment shall
have the operating means projecting
through the metal cabinet or enclosure
so these units can be reset without
locked doors being opened. Enclosures
and metal cabinets shall be locked so
that only authorized qualified persons
have access and shall be marked with a
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ER14FE07.000
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§ 1910.308
29 CFR Ch. XVII (7–1–07 Edition)
sign warning of the presence of energized parts. Collector ring assemblies
on revolving-type machines (shovels,
draglines, etc.) shall be guarded.
(4) Tunnel installation—(i) Application.
The provisions of this paragraph apply
to installation and use of high-voltage
power distribution and utilization
equipment which is portable and/or mobile, such as substations, trailers, cars,
mobile shovels, draglines, hoists, drills,
dredges, compressors, pumps, conveyors, and underground excavators.
(ii) Conductors. Conductors in tunnels
shall be installed in one or more of the
following:
(A) Metal conduit or other metal
raceway,
(B) Type MC cable, or
(C) Other approved multiconductor
cable.
Conductors shall also be so located or
guarded as to protect them from physical damage. Multiconductor portable
cable may supply mobile equipment.
An equipment grounding conductor
shall be run with circuit conductors inside the metal raceway or inside the
multiconductor cable jacket. The
equipment grounding conductor may
be insulated or bare.
(iii) Guarding live parts. Bare terminals of transformers, switches, motor
controllers, and other equipment shall
be enclosed to prevent accidental contact with energized parts. Enclosures
for use in tunnels shall be drip-proof,
weatherproof, or submersible as required by the environmental conditions.
(iv) Disconnecting means. A disconnecting means that simultaneously
opens all ungrounded conductors shall
be installed at each transformer or
motor location.
(v) Grounding and bonding. All nonenergized metal parts of electric equipment and metal raceways and cable
sheaths shall be effectively grounded
and bonded to all metal pipes and rails
at the portal and at intervals not exceeding 1000 feet throughout the tunnel.
(b) Emergency power systems—(1)
Scope. The provisions for emergency
systems apply to circuits, systems, and
equipment intended to supply power
for illumination and special loads, in
the event of failure of the normal supply.
(2) Wiring methods. Emergency circuit
wiring shall be kept entirely independent of all other wiring and equipment and may not enter the same raceway, cable, box, or cabinet or other
wiring except either where common
circuit elements suitable for the purpose are required, or for transferring
power from the normal to the emergency source.
(3) Emergency illumination. Where
emergency lighting is necessary, the
system shall be so arranged that the
failure of any individual lighting element, such as the burning out of a
light bulb, cannot leave any space in
total darkness.
(c) Class 1, Class 2, and Class 3 remote
control, signaling, and power-limited circuits—(1) Classification. Class 1, Class 2,
or Class 3 remote control, signaling, or
power-limited circuits are characterized by their usage and electrical power
limitation which differentiates them
from light and power circuits. These
circuits are classified in accordance
with their respective voltage and power
limitations as summarized in paragraphs (c)(1)(i) through (c)(1)(iii) of this
section.
(i) Class 1 circuits. (A) A Class 1
power-limited circuit is supplied from
a source having a rated output of not
more than 30 volts and 1000 volt-amperes.
(B) A Class 1 remote control circuit
or a Class 1 signaling circuit has a voltage which does not exceed 600 volts;
however, the power output of the
source need not be limited.
(ii) Class 2 and Class 3 circuits. (A)
Power for Class 2 and Class 3 circuits is
limited either inherently (in which no
overcurrent protection is required) or
by a combination of a power source and
overcurrent protection.
(B) The maximum circuit voltage is
150 volts AC or DC for a Class 2 inherently limited power source, and 100
volts AC or DC for a Class 3 inherently
limited power source.
(C) The maximum circuit voltage is
30 volts AC and 60 volts DC for a Class
2 power source limited by overcurrent
protection, and 150 volts AC or DC for
a Class 3 power source limited by overcurrent protection.
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Occupational Safety and Health Admin., Labor
(iii) The maximum circuit voltages
in paragraphs (c)(1)(i) and (c)(1)(ii) of
this section apply to sinusoidal AC or
continuous DC power sources, and
where wet contact occurence is not
likely.
(2) Marking. A Class 2 or Class 3
power supply unit shall be durably
marked where plainly visible to indicate the class of supply and its electrical rating. (See § 1910.302(b)(3).)
(d) Fire protective signaling systems.
(See § 1910.302(b)(3).)
(1) Classifications. Fire protective signaling circuits shall be classified either
as non-power limited or power limited.
(2) Power sources. The power sources
for use with fire protective signaling
circuits shall be either power limited
or nonlimited as follows:
(i) The power supply of non-powerlimited fire protective signaling circuits shall have an output voltage not
in excess of 600 volts.
(ii) The power for power-limited fire
protective signaling circuits shall be
either inherently limited, in which no
overcurrent protection is required, or
limited by a combination of a power
source and overcurrent protection.
(3) Non-power-limited conductor location. Non-power-limited fire protective
signaling circuits and Class 1 circuits
may occupy the same enclosure, cable,
or raceway provided all conductors are
insulated for maximum voltage of any
conductor within the enclosure, cable,
or raceway. Power supply and fire protective signaling circuit conductors are
permitted in the same enclosure, cable,
or raceway only if connected to the
same equipment.
(4) Power-limited conductor location.
Where open conductors are installed,
power-limited fire protective signaling
circuits shall be separated at least 2
inches from conductors of any light,
power, Class 1, and non-power-limited
fire protective signaling circuits unless
a special and equally protective method of conductor separation is employed. Cables and conductors of two or
more power-limited fire protective signaling circuits or Class 3 circuits are
permitted in the same cable, enclosure,
or raceway. Conductors of one or more
Class 2 circuits are permitted within
the same cable, enclosure, or raceway
with conductors of power-limited fire
§ 1910.308
protective signaling circuits provided
that the insulation of Class 2 circuit
conductors in the cable, enclosure, or
raceway is at least that needed for the
power-limited fire protective signaling
circuits.
(5) Identification. Fire protective signaling circuits shall be identified at
terminal and junction locations in a
manner which will prevent unintentional interference with the signaling
circuit during testing and servicing.
Power-limited fire protective signaling
circuits shall be durably marked as
such where plainly visible at terminations.
(e) Communications systems—(1) Scope.
These provisions for communication
systems apply to such systems as central-station-connected and non-central-station-connected telephone circuits, radio and television receiving
and transmitting equipment, including
community antenna television and
radio distribution systems, telegraph,
district messenger, and outside wiring
for fire and burglar alarm, and similar
central station systems. These installations need not comply with the provisions of §§ 1910.303 through 1910.308(d),
except § 1910.304(c)(1) and § 1910.307(b).
(2) Protective devices. (i) Communication circuits so located as to be exposed to accidental contact with light
or power conductors operating at over
300 volts shall have each circuit so exposed provided with a protector approved for the purpose.
(ii) Each conductor of a lead-in from
an outdoor antenna shall be provided
with an antenna discharge unit or
other suitable means that will drain
static charges from the antenna system.
(3) Conductor location—(i) Outside of
buildings. (a) Receiving distribution
lead-in or aerial-drop cables attached
to buildings and lead-in conductors to
radio transmitters shall be so installed
as to avoid the possibility of accidental
contact with electric light or power
conductors.
(b) The clearance between lead-in
conductors and any lightning protection conductors may not be less than 6
feet.
(ii) On poles. Where practicable, communication conductors on poles shall
be located below the light or power
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§ 1910.308
29 CFR Ch. XVII (7–1–07 Edition)
conductors. Communications conductors may not be attached to a crossarm
that carries light or power conductors.
(iii) Inside of buildings. Indoor antennas, lead-ins, and other communication
conductors attached as open conductors to the inside of buildings shall be
located at least 2 inches from conductors of any light or power or Class 1
circuits unless a special and equally
protective method of conductor separation, approved for the purpose, is employed.
(4) Equipment location. Outdoor metal
structures supporting antennas, as well
as self-supporting antennas such as
vertical rods or dipole structures, shall
be located as far away from overhead
conductors of electric light and power
circuits of over 150 volts to ground as
necessary to avoid the possibility of
the antenna or structure falling into or
making accidental contact with such
circuits.
(5) Grounding—(i) Lead-in conductors.
If exposed to contact with electric
light and power conductors, the metal
sheath of aerial cables entering buildings shall be grounded or shall be interrupted close to the entrance to the
building by an insulating joint or
equivalent device. Where protective devices are used, they shall be grounded
in an approved manner.
(ii) Antenna structures. Masts and
metal structures supporting antennas
shall be permanently and effectively
grounded without splice or connection
in the grounding conductor.
(iii) Equipment enclosures. Transmitters shall be enclosed in a metal frame
or grill or separated from the operating
space by a barrier, all metallic parts of
which are effectively connected to
ground. All external metal handles and
controls accessible to the operating
personnel shall be effectively grounded.
Unpowered equipment and enclosures
shall be considered grounded where
connected to an attached coaxial cable
with an effectively grounded metallic
shield.
rfrederick on PROD1PC67 with CFR
[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7,
1981]
EFFECTIVE DATE NOTE: At 72 FR 7212, Feb.
14, 2007, § 1910.308 was revised, effective Aug.
13, 2007. For the convenience of the user, the
revised text is set forth as follows:
§ 1910.308 Special systems.
(a) Systems over 600 volts, nominal. This
paragraph covers the general requirements
for all circuits and equipment operated at
over 600 volts.
(1) Aboveground wiring methods. (i) Aboveground conductors shall be installed in rigid
metal conduit, in intermediate metal conduit, in electrical metallic tubing, in rigid
nonmetallic conduit, in cable trays, as
busways, as cablebus, in other identified
raceways, or as open runs of metal-clad cable
suitable for the use and purpose. In locations
accessible to qualified persons only, open
runs of Type MV cables, bare conductors,
and bare busbars are also permitted. Busbars
shall be either copper or aluminum. Open
runs of insulated wires and cables having a
bare lead sheath or a braided outer covering
shall be supported in a manner designed to
prevent physical damage to the braid or
sheath.
(ii) Conductors emerging from the ground
shall be enclosed in approved raceways.
(2) Braid-covered insulated conductors—open
installations. The braid on open runs of braidcovered insulated conductors shall be flame
retardant or shall have a flame-retardant
saturant applied after installation. This
treated braid covering shall be stripped back
a safe distance at conductor terminals, according to the operating voltage.
(3) Insulation shielding. (i) Metallic and
semiconductor insulation shielding components of shielded cables shall be removed for
a distance dependent on the circuit voltage
and insulation. Stress reduction means shall
be provided at all terminations of factoryapplied shielding.
(ii) Metallic shielding components such as
tapes, wires, or braids, or combinations
thereof, and their associated conducting and
semiconducting components shall be grounded.
(4) Moisture or mechanical protection for
metal-sheathed cables. Where cable conductors
emerge from a metal sheath and where protection against moisture or physical damage
is necessary, the insulation of the conductors shall be protected by a cable sheath terminating device.
(5) Interrupting and isolating devices. (i) Circuit breaker installations located indoors
shall consist of metal-enclosed units or fireresistant cell-mounted units. In locations accessible only to qualified employees, open
mounting of circuit breakers is permitted. A
means of indicating the open and closed position of circuit breakers shall be provided.
(ii) Where fuses are used to protect conductors and equipment, a fuse shall be placed in
each ungrounded conductor. Two power fuses
may be used in parallel to protect the same
load, if both fuses have identical ratings, and
if both fuses are installed in an identified
common mounting with electrical connections that will divide the current equally.
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Occupational Safety and Health Admin., Labor
Power fuses of the vented type may not be
used indoors, underground, or in metal enclosures unless identified for the use.
(iii) Fused cutouts installed in buildings or
transformer vaults shall be of a type identified for the purpose. Distribution cutouts
may not be used indoors, underground, or in
metal enclosures. They shall be readily accessible for fuse replacement.
(iv) Where fused cutouts are not suitable to
interrupt the circuit manually while carrying full load, an approved means shall be
installed to interrupt the entire load. Unless
the fused cutouts are interlocked with the
switch to prevent opening of the cutouts
under load, a conspicuous sign shall be
placed at such cutouts reading: ‘‘WARNING—DO NOT OPERATE UNDER LOAD.’’
(v) Suitable barriers or enclosures shall be
provided to prevent contact with nonshielded
cables or energized parts of oil-filled cutouts.
(vi) Load interrupter switches may be used
only if suitable fuses or circuits are used in
conjunction with these devices to interrupt
fault currents.
(A) Where these devices are used in combination, they shall be coordinated electrically so that they will safely withstand
the effects of closing, carrying, or interrupting all possible currents up to the assigned maximum short-circuit rating.
(B) Where more than one switch is installed with interconnected load terminals
to provide for alternate connection to different supply conductors, each switch shall
be provided with a conspicuous sign reading:
‘‘WARNING—SWITCH MAY BE ENERGIZED
BY BACKFEED.’’
(vii) A means (for example, a fuseholder
and fuse designed for the purpose) shall be
provided to completely isolate equipment for
inspection and repairs. Isolating means that
are not designed to interrupt the load current of the circuit shall be either interlocked
with an approved circuit interrupter or provided with a sign warning against opening
them under load.
(6) Mobile and portable equipment. (i) A metallic enclosure shall be provided on the mobile machine for enclosing the terminals of
the power cable. The enclosure shall include
provisions for a solid connection for the
grounding terminal to effectively ground the
machine frame. The method of cable termination used shall prevent any strain or pull
on the cable from stressing the electrical
connections. The enclosure shall have provision for locking so only authorized qualified
persons may open it and shall be marked
with a sign warning of the presence of energized parts.
(ii) All energized switching and control
parts shall be enclosed in effectively grounded metal cabinets or enclosures. Circuit
breakers and protective equipment shall
have the operating means projecting through
the metal cabinet or enclosure so these units
§ 1910.308
can be reset without locked doors being
opened. Enclosures and metal cabinets shall
be locked so that only authorized qualified
persons have access and shall be marked
with a sign warning of the presence of energized parts. Collector ring assemblies on revolving-type machines (shovels, draglines,
etc.) shall be guarded.
(7) Tunnel installations. This paragraph applies to installation and use of high-voltage
power distribution and utilization equipment
that is portable or mobile, such as substations, trailers, cars, mobile shovels, draglines, hoists, drills, dredges, compressors,
pumps, conveyors, and underground excavators.
(i) Conductors in tunnels shall be installed
in one or more of the following:
(A) Metal conduit or other metal raceway;
(B) Type MC cable; or
(C) Other approved multiconductor cable.
(ii) Multiconductor portable cable may
supply mobile equipment.
(iii) Conductors and cables shall also be so
located or guarded as to protect them from
physical damage. An equipment grounding
conductor shall be run with circuit conductors inside the metal raceway or inside the
multiconductor cable jacket. The equipment
grounding conductor may be insulated or
bare.
(iv) Bare terminals of transformers,
switches, motor controllers, and other equipment shall be enclosed to prevent accidental
contact with energized parts.
(v) Enclosures for use in tunnels shall be
drip-proof, weatherproof, or submersible as
required by the environmental conditions.
(vi) Switch or contactor enclosures may
not be used as junction boxes or raceways for
conductors feeding through or tapping off to
other switches, unless special designs are
used to provide adequate space for this purpose.
(vii) A disconnecting means that simultaneously opens all ungrounded conductors
shall be installed at each transformer or
motor location.
(viii) All nonenergized metal parts of electric equipment and metal raceways and cable
sheaths shall be effectively grounded and
bonded to all metal pipes and rails at the
portal and at intervals not exceeding 305 m
(1000 ft) throughout the tunnel.
(b) Emergency power systems. This paragraph applies to circuits, systems, and equipment intended to supply power for illumination and special loads in the event of failure
of the normal supply.
(1) Wiring methods. Emergency circuit wiring shall be kept entirely independent of all
other wiring and equipment and may not
enter the same raceway, cable, box, or cabinet or other wiring except either where common circuit elements suitable for the purpose are required, or for transferring power
from the normal to the emergency source.
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§ 1910.308
29 CFR Ch. XVII (7–1–07 Edition)
(2) Emergency illumination. Emergency illumination shall include all required means of
egress lighting, illuminated exit signs, and
all other lights necessary to provide illumination. Where emergency lighting is necessary, the system shall be so arranged that
the failure of any individual lighting element, such as the burning out of a light bulb,
cannot leave any space in total darkness.
(3) Signs. (i) A sign shall be placed at the
service entrance equipment indicating the
type and location of on-site emergency
power sources. However, a sign is not required for individual unit equipment.
(ii) Where the grounded circuit conductor
connected to the emergency source is connected to a grounding electrode conductor at
a location remote from the emergency
source, there shall be a sign at the grounding
location that shall identify all emergency
and normal sources connected at that location.
(c) Class 1, Class 2, and Class 3 remote control, signaling, and power-limited circuits—(1)
Classification. Class 1, Class 2, and Class 3 remote control, signaling, or power-limited
circuits are characterized by their usage and
electrical power limitation that differentiates them from light and power circuits.
These circuits are classified in accordance
with their respective voltage and power limitations as summarized in paragraphs (c)(1)(i)
through (c)(1)(iii) of this section.
(i) A Class 1 power-limited circuit shall be
supplied from a source having a rated output
of not more than 30 volts and 1000 volt-amperes.
(ii) A Class 1 remote control circuit or a
Class 1 signaling circuit shall have a voltage
not exceeding 600 volts; however, the power
output of the source need not be limited.
(iii) The power source for a Class 2 or Class
3 circuit shall be listed equipment marked as
a Class 2 or Class 3 power source, except as
follows:
(A) Thermocouples do not require listing
as a Class 2 power source; and
(B) A dry cell battery is considered an inherently limited Class 2 power source, provided the voltage is 30 volts or less and the
capacity is less than or equal to that available from series-connected No. 6 carbon zinc
cells.
(2) Marking. A Class 2 or Class 3 power supply unit shall be durably marked where
plainly visible to indicate the class of supply
and its electrical rating.
(3) Separation from conductors of other circuits. Cables and conductors of Class 2 and
Class 3 circuits may not be placed in any
cable, cable tray, compartment, enclosure,
manhole, outlet box, device box, raceway, or
similar fitting with conductors of electric
light, power, Class 1, nonpower-limited fire
alarm circuits, and medium power networkpowered broadband communications cables
unless a barrier or other equivalent form of
protection against contact is employed.
(d) Fire alarm systems—(1) Classifications.
Fire alarm circuits shall be classified either
as nonpower limited or power limited.
(2) Power sources. The power sources for use
with fire alarm circuits shall be either power
limited or nonpower limited as follows:
(i) The power source of nonpower-limited
fire alarm (NPLFA) circuits shall have an
output voltage of not more than 600 volts,
nominal; and
(ii) The power source for a power-limited
fire alarm (PLFA) circuit shall be listed
equipment marked as a PLFA power source.
(3) Separation from conductors of other circuits. (i) Nonpower-limited fire alarm circuits and Class 1 circuits may occupy the
same enclosure, cable, or raceway provided
all conductors are insulated for maximum
voltage of any conductor within the enclosure, cable, or raceway. Power supply and
fire alarm circuit conductors are permitted
in the same enclosure, cable, or raceway
only if connected to the same equipment.
(ii) Power-limited circuit cables and conductors may not be placed in any cable,
cable tray, compartment, enclosure, outlet
box, raceway, or similar fitting with conductors of electric light, power, Class 1,
nonpower-limited fire alarm circuit conductors, or medium power network-powered
broadband communications circuits.
(iii) Power-limited fire alarm circuit conductors shall be separated at least 50.8 mm (2
in.) from conductors of any electric light,
power, Class 1, nonpower-limited fire alarm,
or
medium
power
network-powered
broadband communications circuits unless a
special and equally protective method of
conductor separation is employed.
(iv) Conductors of one or more Class 2 circuits are permitted within the same cable,
enclosure, or raceway with conductors of
power-limited fire alarm circuits provided
that the insulation of Class 2 circuit conductors in the cable, enclosure, or raceway is at
least that needed for the power-limited fire
alarm circuits.
(4) Identification. Fire alarm circuits shall
be identified at terminal and junction locations in a manner that will prevent unintentional interference with the signaling circuit
during testing and servicing. Power-limited
fire alarm circuits shall be durably marked
as such where plainly visible at terminations.
(e) Communications systems. This paragraph
applies to central-station-connected and
non-central-station-connected telephone circuits, radio and television receiving and
transmitting equipment, including community antenna television and radio distribution systems, telegraph, district messenger,
and outside wiring for fire and burglar
alarm, and similar central station systems.
These installations need not comply with the
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provisions of § 1910.303 through § 1910.308(d),
except for § 1910.304(c)(1) and § 1910.307.
(1) Protective devices. (i) A listed primary
protector shall be provided on each circuit
run partly or entirely in aerial wire or aerial
cable not confined within a block.
(ii) A listed primary protector shall be also
provided on each aerial or underground circuit when the location of the circuit within
the block containing the building served allows the circuit to be exposed to accidental
contact with electric light or power conductors operating at over 300 volts to ground.
(iii) In addition, where there exists a lightning exposure, each interbuilding circuit on
premises shall be protected by a listed primary protector at each end of the interbuilding circuit.
(2) Conductor location. (i) Lead-in or aerialdrop cables from a pole or other support, including the point of initial attachment to a
building or structure, shall be kept away
from electric light, power, Class 1, or
nonpower-limited fire alarm circuit conductors so as to avoid the possibility of accidental contact.
(ii) A separation of at least 1.83 m (6 ft)
shall be maintained between communications wires and cables on buildings and lightning conductors.
(iii) Where communications wires and cables and electric light or power conductors
are supported by the same pole or run parallel to each other in-span, the following
conditions shall be met:
(A) Where practicable, communication
wires and cables on poles shall be located
below the electric light or power conductors;
and
(B) Communications wires and cables may
not be attached to a crossarm that carries
electric light or power conductors.
(iv) Indoor communications wires and cables shall be separated at least 50.8 mm (2
in.) from conductors of any electric light,
power, Class 1, nonpower-limited fire alarm,
or
medium
power
network-powered
broadband communications circuits, unless a
special and equally protective method of
conductor separation, identified for the purpose, is employed.
(3) Equipment location. Outdoor metal
structures supporting antennas, as well as
self-supporting antennas such as vertical
rods or dipole structures, shall be located as
far away from overhead conductors of electric light and power circuits of over 150 volts
to ground as necessary to prevent the antenna or structure from falling into or making accidental contact with such circuits.
(4) Grounding. (i) If exposed to contact with
electric light and power conductors, the
metal sheath of aerial cables entering buildings shall be grounded or shall be interrupted close to the entrance to the building
by an insulating joint or equivalent device.
§ 1910.308
Where protective devices are used, they shall
be grounded in an approved manner.
(ii) Masts and metal structures supporting
antennas shall be permanently and effectively grounded without splice or connection
in the grounding conductor.
(iii) Transmitters shall be enclosed in a
metal frame or grill or separated from the
operating space by a barrier, all metallic
parts of which are effectively connected to
ground. All external metal handles and controls accessible to the operating personnel
shall be effectively grounded. Unpowered
equipment and enclosures are considered to
be grounded where connected to an attached
coaxial cable with an effectively grounded
metallic shield.
(f) Solar photovoltaic systems. This paragraph covers solar photovoltaic systems that
can be interactive with other electric power
production sources or can stand alone with
or without electrical energy storage such as
batteries. These systems may have ac or dc
output for utilization.
(1) Conductors of different systems. Photovoltaic source circuits and photovoltaic output circuits may not be contained in the
same raceway, cable tray, cable, outlet box,
junction box, or similar fitting as feeders or
branch circuits of other systems, unless the
conductors of the different systems are separated by a partition or are connected together.
(2) Disconnecting means. Means shall be provided to disconnect all current-carrying conductors of a photovoltaic power source from
all other conductors in a building or other
structure. Where a circuit grounding connection is not designed to be automatically interrupted as part of the ground-fault protection system, a switch or circuit breaker used
as disconnecting means may not have a pole
in the grounded conductor.
(g) Integrated electrical systems—(1) Scope.
Paragraph (g) of this section covers integrated electrical systems, other than unit
equipment, in which orderly shutdown is
necessary to ensure safe operation. An integrated electrical system as used in this section shall be a unitized segment of an industrial wiring system where all of the following conditions are met:
(i) An orderly shutdown process minimizes
employee hazard and equipment damage;
(ii) The conditions of maintenance and supervision ensure that only qualified persons
will service the system; and
(iii) Effective safeguards are established
and maintained.
(2) Location of overcurrent devices in or on
premises. Overcurrent devices that are critical to integrated electrical systems need
not be readily accessible to employees as required by § 1910.304(f)(1)(iv) if they are located with mounting heights to ensure security from operation by nonqualified persons.
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§§ 1910.309–1910.330
§§ 1910.309–1910.330
29 CFR Ch. XVII (7–1–07 Edition)
[Reserved]
SAFETY-RELATED WORK PRACTICES
§ 1910.331
Scope.
(a) Covered work by both qualified and
unqualified persons. The provisions of
§§ 1910.331 through 1910.335 cover electrical safety-related work practices for
both qualified persons (those who have
training in avoiding the electrical hazards of working on or near exposed energized parts) and unqualified persons
(those with little or no such training)
working on, near, or with the following
installations:
(1) Premises wiring. Installations of
electric conductors and equipment
within or on buildings or other structures, and on other premises such as
yards, carnival, parking, and other
lots, and industrial substations;
(2) Wiring for connection to supply. Installations of conductors that connect
to the supply of electricity; and
(3) Other wiring. Installations of other
outside conductors on the premises.
(4) Optical fiber cable. Installations of
optical fiber cable where such installations are made along with electric conductors.
NOTE: See § 1910.399 for the definition of
‘‘qualified person.’’ See § 1910.332 for training
requirements that apply to qualified and unqualified persons.
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(b) Other covered work by unqualified
persons. The provisions of §§ 1910.331
through 1910.335 also cover work performed by unqualified persons on, near,
or with the installations listed in paragraphs (c)(1) through (c)(4) of this section.
(c) Excluded work by qualified persons.
The provisions of §§ 1910.331 through
1910.335 do not apply to work performed
by qualified persons on or directly associated with the following installations:
(1) Generation, transmission, and distribution installations. Installations for
the
generation,
control,
transformation, transmission, and distribution of electric energy (including communication and metering) located in
buildings used for such purposes or located outdoors.
NOTE 1: Work on or directly associated
with installations of utilization equipment
used for purposes other than generating,
transmitting, or distributing electric energy
(such as installations which are in office
buildings, warehouses, garages, machine
shops, or recreational buildings, or other utilization installations which are not an integral part of a generating installation, substation, or control center) is covered under
paragraph (a)(1) of this section.
NOTE 2: For work on or directly associated
with utilization installations, an employer
who complies with the work practices of
§ 1910.269 (electric power generation, transmission, and distribution) will be deemed to
be in compliance with § 1910.333(c) and
§ 1910.335. However, the requirements of
§ 1910.332,
§ 1910.333(a),
§ 1910.333(b),
and
§ 1910.334 apply to all work on or directly associated with utilization installations, regardless of whether the work is performed by
qualified or unqualified persons.
NOTE 3: Work on or directly associated
with generation, transmission, or distribution installations includes:
(1) Work performed directly on such installations, such as repairing overhead or underground distribution lines or repairing a feedwater pump for the boiler in a generating
plant.
(2) Work directly associated with such installations, such as line-clearance tree trimming and replacing utility poles.
(3) Work on electric utilization circuits in
a generating plant provided that:
(A) Such circuits are commingled with installations of power generation equipment or
circuits, and
(B) The generation equipment or circuits
present greater electrical hazards than those
posed by the utilization equipment or circuits (such as exposure to higher voltages or
lack of overcurrent protection).
This work is covered by § 1910.269 of this
Part.
(2) Communications installations. Installations of communication equipment to the extent that the work is
covered under § 1910.268.
(3) Installations in vehicles. Installations in ships, watercraft, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles.
(4) Railway installations. Installations
of railways for generation, transformation, transmission, or distribution of power used exclusively for operation of rolling stock or installations
of railways used exclusively for signaling and communication purposes.
[55 FR 32016, Aug. 6, 1990, as amended at 59
FR 4476, Jan. 31, 1994]
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Occupational Safety and Health Admin., Labor
§ 1910.332 Training.
(a) Scope. The training requirements
contained in this section apply to employees who face a risk of electric
shock that is not reduced to a safe
level by the electrical installation requirements
of
§§ 1910.303
through
1910.308.
NOTE: Employees in occupations listed in
Table S–4 face such a risk and are required
to be trained. Other employees who also may
reasonably be expected to face a comparable
risk of injury due to electric shock or other
electrical hazards must also be trained.
(b) Content of training—(1) Practices
addressed in this standard. Employees
shall be trained in and familiar with
the safety-related work practices required by §§ 1910.331 through 1910.335
that pertain to their respective job assignments.
(2) Additional requirements for unqualified persons. Employees who are covered by paragraph (a) of this section
but who are not qualified persons shall
also be trained in and familiar with
any electrically related safety practices not specifically addressed by
§§ 1910.331 through 1910.335 but which
are necessary for their safety.
(3) Additional requirements for qualified
persons. Qualified persons (i.e., those
permitted to work on or near exposed
energized parts) shall, at a minimum,
be trained in and familiar with the following:
(i) The skills and techniques necessary to distinguish exposed live parts
from other parts of electric equipment,
(ii) The skills and techniques necessary to determine the nominal voltage of exposed live parts, and
(iii) The clearance distances specified
in § 1910.333(c) and the corresponding
voltages to which the qualified person
will be exposed.
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NOTE 1: For the purposes of §§ 1910.331
through 1910.335, a person must have the
training required by paragraph (b)(3) of this
section in order to be considered a qualified
person.
NOTE 2: Qualified persons whose work on
energized equipment involves either direct
contact or contact by means of tools or materials must also have the training needed to
meet § 1910.333(c)(2).
(c) Type of training. The training required by this section shall be of the
classroom or on-the-job type. The de-
§ 1910.333
gree of training provided shall be determined by the risk to the employee.
TABLE S–4—TYPICAL OCCUPATIONAL CATEGORIES OF EMPLOYEES FACING A HIGHER
THAN NORMAL RISK OF ELECTRICAL ACCIDENT
Occupation
supervisors.1
Blue collar
Electrical and electronic engineers.1
Electrical and electronic equipment assemblers.1
Electrical and electronic technicians.1
Electricians.
Industrial machine operators.1
Material handling equipment operators.1
Mechanics and repairers.1
Painters.1
Riggers and roustabouts.1
Stationary engineers.1
Welders.
1 Workers in these groups do not need to be trained if their
work or the work of those they supervise does not bring them
or the employees they supervise close enough to exposed
parts of electric circuits operating at 50 volts or more to
ground for a hazard to exist.
[55 FR 32016, Aug. 6, 1990]
§ 1910.333 Selection and use of work
practices.
(a) General. Safety-related work practices shall be employed to prevent electric shock or other injuries resulting
from either direct or indirect electrical
contacts, when work is performed near
or on equipment or circuits which are
or may be energized. The specific safety-related work practices shall be consistent with the nature and extent of
the associated electrical hazards.
(1) Deenergized parts. Live parts to
which an employee may be exposed
shall be deenergized before the employee works on or near them, unless
the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to
equipment design or operational limitations. Live parts that operate at less
than 50 volts to ground need not be deenergized if there will be no increased
exposure to electrical burns or to explosion due to electric arcs.
NOTE 1: Examples of increased or additional hazards include interruption of life
support equipment, deactivation of emergency alarm systems, shutdown of hazardous
location ventilation equipment, or removal
of illumination for an area.
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§ 1910.333
29 CFR Ch. XVII (7–1–07 Edition)
NOTE 2: Examples of work that may be performed on or near energized circuit parts because of infeasibility due to equipment design or operational limitations include testing of electric circuits that can only be performed with the circuit energized and work
on circuits that form an integral part of a
continuous industrial process in a chemical
plant that would otherwise need to be completely shut down in order to permit work on
one circuit or piece of equipment.
NOTE 3: Work on or near deenergized parts
is covered by paragraph (b) of this section.
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(2) Energized parts. If the exposed live
parts are not deenergized (i.e., for reasons of increased or additional hazards
or infeasibility), other safety-related
work practices shall be used to protect
employees who may be exposed to the
electrical hazards involved. Such work
practices shall protect employees
against contact with energized circuit
parts directly with any part of their
body or indirectly through some other
conductive object. The work practices
that are used shall be suitable for the
conditions under which the work is to
be performed and for the voltage level
of the exposed electric conductors or
circuit parts. Specific work practice requirements are detailed in paragraph
(c) of this section.
(b) Working on or near exposed deenergized parts—(1) Application. This paragraph applies to work on exposed deenergized parts or near enough to them
to expose the employee to any electrical hazard they present. Conductors
and parts of electric equipment that
have been deenergized but have not
been locked out or tagged in accordance with paragraph (b) of this section
shall be treated as energized parts, and
paragraph (c) of this section applies to
work on or near them.
(2) Lockout and tagging. While any
employee is exposed to contact with
parts of fixed electric equipment or circuits which have been deenergized, the
circuits energizing the parts shall be
locked out or tagged or both in accordance with the requirements of this
paragraph. The requirements shall be
followed in the order in which they are
presented (i.e., paragraph (b)(2)(i) first,
then paragraph (b)(2)(ii), etc.).
NOTE 1: As used in this section, fixed equipment refers to equipment fastened in place
or connected by permanent wiring methods.
NOTE 2: Lockout and tagging procedures
that comply with paragraphs (c) through (f)
of § 1910.147 will also be deemed to comply
with paragraph (b)(2) of this section provided
that:
(1) The procedures address the electrical
safety hazards covered by this Subpart; and
(2) The procedures also incorporate the requirements of paragraphs (b)(2)(iii)(D) and
(b)(2)(iv)(B) of this section.
(i) Procedures. The employer shall
maintain a written copy of the procedures outlined in paragraph (b)(2) and
shall make it available for inspection
by employees and by the Assistant Secretary of Labor and his or her authorized representatives.
NOTE: The written procedures may be in
the form of a copy of paragraph (b) of this
section.
(ii) Deenergizing equipment. (A) Safe
procedures for deenergizing circuits
and equipment shall be determined before circuits or equipment are deenergized.
(B) The circuits and equipment to be
worked on shall be disconnected from
all electric energy sources. Control circuit devices, such as push buttons, selector switches, and interlocks, may
not be used as the sole means for deenergizing circuits or equipment. Interlocks for electric equipment may not
be used as a substitute for lockout and
tagging procedures.
(C) Stored electric energy which
might endanger personnel shall be released. Capacitors shall be discharged
and high capacitance elements shall be
short-circuited and grounded, if the
stored electric energy might endanger
personnel.
NOTE: If the capacitors or associated equipment are handled in meeting this requirement, they shall be treated as energized.
(D) Stored non-electrical energy in
devices that could reenergize electric
circuit parts shall be blocked or relieved to the extent that the circuit
parts could not be accidentally energized by the device.
(iii) Application of locks and tags. (A)
A lock and a tag shall be placed on
each disconnecting means used to deenergize circuits and equipment on
which work is to be performed, except
as provided in paragraphs (b)(2)(iii)(C)
and (b)(2)(iii)(E) of this section. The
lock shall be attached so as to prevent
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Occupational Safety and Health Admin., Labor
persons from operating the disconnecting means unless they resort to
undue force or the use of tools.
(B) Each tag shall contain a statement prohibiting unauthorized operation of the disconnecting means and
removal of the tag.
(C) If a lock cannot be applied, or if
the employer can demonstrate that
tagging procedures will provide a level
of safety equivalent to that obtained
by the use of a lock, a tag may be used
without a lock.
(D) A tag used without a lock, as permitted by paragraph (b)(2)(iii)(C) of
this section, shall be supplemented by
at least one additional safety measure
that provides a level of safety equivalent to that obtained by the use of a
lock. Examples of additional safety
measures include the removal of an
isolating circuit element, blocking of a
controlling switch, or opening of an
extra disconnecting device.
(E) A lock may be placed without a
tag only under the following conditions:
(1) Only one circuit or piece of equipment is deenergized, and
(2) The lockout period does not extend beyond the work shift, and
(3) Employees exposed to the hazards
associated with reenergizing the circuit or equipment are familiar with
this procedure.
(iv) Verification of deenergized condition. The requirements of this paragraph shall be met before any circuits
or equipment can be considered and
worked as deenergized.
(A) A qualified person shall operate
the equipment operating controls or
otherwise verify that the equipment
cannot be restarted.
(B) A qualified person shall use test
equipment to test the circuit elements
and electrical parts of equipment to
which employees will be exposed and
shall verify that the circuit elements
and equipment parts are deenergized.
The test shall also determine if any energized condition exists as a result of
inadvertently induced voltage or unrelated voltage backfeed even though
specific parts of the circuit have been
deenergized and presumed to be safe. If
the circuit to be tested is over 600
volts, nominal, the test equipment
shall be checked for proper operation
§ 1910.333
immediately before and immediately
after this test.
(v) Reenergizing equipment. These requirements shall be met, in the order
given, before circuits or equipment are
reenergized, even temporarily.
(A) A qualified person shall conduct
tests and visual inspections, as necessary, to verify that all tools, electrical jumpers, shorts, grounds, and
other such devices have been removed,
so that the circuits and equipment can
be safely energized.
(B) Employees exposed to the hazards
associated with reenergizing the circuit or equipment shall be warned to
stay clear of circuits and equipment.
(C) Each lock and tag shall be removed by the employee who applied it
or under his or her direct supervision.
However, if this employee is absent
from the workplace, then the lock or
tag may be removed by a qualified person designated to perform this task
provided that:
(1) The employer ensures that the
employee who applied the lock or tag
is not available at the workplace, and
(2) The employer ensures that the
employee is aware that the lock or tag
has been removed before he or she resumes work at that workplace.
(D) There shall be a visual determination that all employees are clear
of the circuits and equipment.
(c) Working on or near exposed energized parts—(1) Application. This paragraph applies to work performed on exposed live parts (involving either direct
contact or contact by means of tools or
materials) or near enough to them for
employees to be exposed to any hazard
they present.
(2) Work on energized equipment. Only
qualified persons may work on electric
circuit parts or equipment that have
not been deenergized under the procedures of paragraph (b) of this section.
Such persons shall be capable of working safely on energized circuits and
shall be familiar with the proper use of
special precautionary techniques, personal protective equipment, insulating
and shielding materials, and insulated
tools.
(3) Overhead lines. If work is to be
performed near overhead lines, the
lines shall be deenergized and grounded, or other protective measures shall
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§ 1910.333
29 CFR Ch. XVII (7–1–07 Edition)
be provided before work is started. If
the lines are to be deenergized, arrangements shall be made with the person or organization that operates or
controls the electric circuits involved
to deenergize and ground them. If protective measures, such as guarding,
isolating, or insulating are provided,
these precautions shall prevent employees from contacting such lines directly with any part of their body or
indirectly through conductive materials, tools, or equipment.
NOTE: The work practices used by qualified
persons installing insulating devices on overhead power transmission or distribution
lines are covered by § 1910.269 of this Part,
not by § § 1910.332 through 1910.335 of this
Part. Under paragraph (c)(2) of this section,
unqualified persons are prohibited from performing this type of work.
(i) Unqualified persons. (A) When an
unqualified person is working in an elevated position near overhead lines, the
location shall be such that the person
and the longest conductive object he or
she may contact cannot come closer to
any unguarded, energized overhead line
than the following distances:
(1) For voltages to ground 50kV or
below—10 ft. (305 cm);
(2) For voltages to ground over
50kV—10 ft. (305 cm) plus 4 in. (10 cm)
for every 10kV over 50kV.
(B) When an unqualified person is
working on the ground in the vicinity
of overhead lines, the person may not
bring any conductive object closer to
unguarded, energized overhead lines
than the distances given in paragraph
(c)(3)(i)(A) of this section.
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NOTE: For voltages normally encountered
with overhead power lines, objects which do
not have an insulating rating for the voltage
involved are considered to be conductive.
(ii) Qualified persons. When a qualified person is working in the vicinity of
overhead lines, whether in an elevated
position or on the ground, the person
may not approach or take any conductive object without an approved insulating handle closer to exposed energized parts than shown in Table S–5 unless:
(A) The person is insulated from the
energized part (gloves, with sleeves if
necessary, rated for the voltage involved are considered to be insulation
of the person from the energized part
on which work is performed), or
(B) The energized part is insulated
both from all other conductive objects
at a different potential and from the
person, or
(C) The person is insulated from all
conductive objects at a potential different from that of the energized part.
TABLE S–5—APPROACH DISTANCES FOR
QUALIFIED EMPLOYEES—ALTERNATING CURRENT
Voltage range (phase to
phase)
300V and less ........................
Over 300V, not over 750V ....
Over 750V, not over 2kV .......
Over 2kV, not over 15kV .......
Over 15kV, not over 37kV .....
Over 37kV, not over 87.5kV ..
Over 87.5kV, not over 121kV
Over 121kV, not over 140kV
Minimum approach distance
Avoid contact.
1 ft. 0 in. (30.5 cm).
l ft. 6 in. (46 cm).
2 ft. 0 in. (61 cm).
3 ft. 0 in. (91 cm).
3 ft. 6 in. (107 cm).
4 ft. 0 in. (122 cm).
4 ft. 6 in. (137 cm).
(iii) Vehicular and mechanical equipment. (A) Any vehicle or mechanical
equipment capable of having parts of
its structure elevated near energized
overhead lines shall be operated so that
a clearance of 10 ft. (305 cm) is maintained. If the voltage is higher than
50kV, the clearance shall be increased 4
in. (10 cm) for every 10kV over that
voltage. However, under any of the following conditions, the clearance may
be reduced:
(1) If the vehicle is in transit with its
structure lowered, the clearance may
be reduced to 4 ft. (122 cm). If the voltage is higher than 50kV, the clearance
shall be increased 4 in. (10 cm) for
every 10kV over that voltage.
(2) If insulating barriers are installed
to prevent contact with the lines, and
if the barriers are rated for the voltage
of the line being guarded and are not a
part of or an attachment to the vehicle
or its raised structure, the clearance
may be reduced to a distance within
the designed working dimensions of the
insulating barrier.
(3) If the equipment is an aerial lift
insulated for the voltage involved, and
if the work is performed by a qualified
person, the clearance (between the
uninsulated portion of the aerial lift
and the power line) may be reduced to
the distance given in Table S–5.
(B) Employees standing on the
ground may not contact the vehicle or
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Occupational Safety and Health Admin., Labor
mechanical equipment or any of its attachments, unless:
(1) The employee is using protective
equipment rated for the voltage; or
(2) The equipment is located so that
no uninsulated part of its structure
(that portion of the structure that provides a conductive path to employees
on the ground) can come closer to the
line than permitted in paragraph
(c)(3)(iii) of this section.
(C) If any vehicle or mechanical
equipment capable of having parts of
its structure elevated near energized
overhead lines is intentionally grounded, employees working on the ground
near the point of grounding may not
stand at the grounding location whenever there is a possibility of overhead
line contact. Additional precautions,
such as the use of barricades or insulation, shall be taken to protect employees from hazardous ground potentials,
depending on earth resistivity and
fault currents, which can develop within the first few feet or more outward
from the grounding point.
(4) Illumination. (i) Employees may
not enter spaces containing exposed energized parts, unless illumination is
provided that enables the employees to
perform the work safely.
(ii) Where lack of illumination or an
obstruction precludes observation of
the work to be performed, employees
may not perform tasks near exposed
energized parts. Employees may not
reach blindly into areas which may
contain energized parts.
(5) Confined or enclosed work spaces.
When an employee works in a confined
or enclosed space (such as a manhole or
vault) that contains exposed energized
parts, the employer shall provide, and
the employee shall use, protective
shields, protective barriers, or insulating materials as necessary to avoid
inadvertent contact with these parts.
Doors, hinged panels, and the like shall
be secured to prevent their swinging
into an employee and causing the employee to contact exposed energized
parts.
(6) Conductive materials and equipment.
Conductive materials and equipment
that are in contact with any part of an
employee’s body shall be handled in a
manner that will prevent them from
contacting exposed energized conduc-
§ 1910.334
tors or circuit parts. If an employee
must handle long dimensional conductive objects (such as ducts and pipes) in
areas with exposed live parts, the employer shall institute work practices
(such as the use of insulation, guarding, and material handling techniques)
which will minimize the hazard.
(7) Portable ladders. Portable ladders
shall have nonconductive siderails if
they are used where the employee or
the ladder could contact exposed energized parts.
(8) Conductive apparel. Conductive articles of jewelry and clothing (such as
watch bands, bracelets, rings, key
chains, necklaces, metalized aprons,
cloth with conductive thread, or metal
headgear) may not be worn if they
might contact exposed energized parts.
However, such articles may be worn if
they are rendered nonconductive by
covering, wrapping, or other insulating
means.
(9) Housekeeping duties. Where live
parts present an electrical contact hazard, employees may not perform housekeeping duties at such close distances
to the parts that there is a possibility
of contact, unless adequate safeguards
(such as insulating equipment or barriers) are provided. Electrically conductive cleaning materials (including
conductive solids such as steel wool,
metalized cloth, and silicon carbide, as
well as conductive liquid solutions)
may not be used in proximity to energized parts unless procedures are followed which will prevent electrical
contact.
(10) Interlocks. Only a qualified person
following the requirements of paragraph (c) of this section may defeat an
electrical safety interlock, and then
only temporarily while he or she is
working on the equipment. The interlock system shall be returned to its operable condition when this work is
completed.
[55 FR 32016, Aug. 6, 1990; 55 FR 42053, Nov. 1,
1990, as amended at 59 FR 4476, Jan. 31, 1994]
§ 1910.334 Use of equipment.
(a) Portable electric equipment. This
paragraph applies to the use of cordand plug-connected equipment, including flexible cord sets (extension cords).
(1) Handling. Portable equipment
shall be handled in a manner which
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§ 1910.334
29 CFR Ch. XVII (7–1–07 Edition)
will not cause damage. Flexible electric cords connected to equipment may
not be used for raising or lowering the
equipment. Flexible cords may not be
fastened with staples or otherwise
hung in such a fashion as could damage
the outer jacket or insulation.
(2) Visual inspection. (i) Portable cordand plug-connected equipment and
flexible cord sets (extension cords)
shall be visually inspected before use
on any shift for external defects (such
as loose parts, deformed and missing
pins, or damage to outer jacket or insulation) and for evidence of possible
internal damage (such as pinched or
crushed outer jacket). Cord- and plugconnected equipment and flexible cord
sets (extension cords) which remain
connected once they are put in place
and are not exposed to damage need
not be visually inspected until they are
relocated.
(ii) If there is a defect or evidence of
damage that might expose an employee
to injury, the defective or damaged
item shall be removed from service,
and no employee may use it until repairs and tests necessary to render the
equipment safe have been made.
(iii) When an attachment plug is to
be connected to a receptacle (including
any on a cord set), the relationship of
the plug and receptacle contacts shall
first be checked to ensure that they are
of proper mating configurations.
(3) Grounding-type equipment. (i) A
flexible cord used with grounding-type
equipment shall contain an equipment
grounding conductor.
(ii) Attachment plugs and receptacles
may not be connected or altered in a
manner which would prevent proper
continuity of the equipment grounding
conductor at the point where plugs are
attached to receptacles. Additionally,
these devices may not be altered to
allow the grounding pole of a plug to be
inserted into slots intended for connection to the current-carrying conductors.
(iii) Adapters which interrupt the
continuity of the equipment grounding
connection may not be used.
(4) Conductive work locations. Portable
electric equipment and flexible cords
used in highly conductive work locations (such as those inundated with
water or other conductive liquids), or
in job locations where employees are
likely to contact water or conductive
liquids, shall be approved for those locations.
(5) Connecting attachment plugs. (i)
Employees’ hands may not be wet when
plugging and unplugging flexible cords
and cord- and plug-connected equipment, if energized equipment is involved.
(ii) Energized plug and receptacle
connections may be handled only with
insulating protective equipment if the
condition of the connection could provide a conducting path to the employee’s hand (if, for example, a cord connector is wet from being immersed in
water).
(iii) Locking-type connectors shall be
properly secured after connection.
(b) Electric power and lighting circuits—(1) Routine opening and closing of
circuits. Load rated switches, circuit
breakers, or other devices specifically
designed as disconnecting means shall
be used for the opening, reversing, or
closing of circuits under load conditions. Cable connectors not of the loadbreak type, fuses, terminal lugs, and
cable splice connections may not be
used for such purposes, except in an
emergency.
(2) Reclosing circuits after protective device operation. After a circuit is deenergized by a circuit protective device, the
circuit may not be manually reenergized until it has been determined that
the equipment and circuit can be safely
energized. The repetitive manual reclosing of circuit breakers or reenergizing circuits through replaced fuses
is prohibited.
NOTE: When it can be determined from the
design of the circuit and the overcurrent devices involved that the automatic operation
of a device was caused by an overload rather
than a fault condition, no examination of the
circuit or connected equipment is needed before the circuit is reenergized.
(3) Overcurrent protection modification.
Overcurrent protection of circuits and
conductors may not be modified, even
on a temporary basis, beyond that allowed by § 1910.304(e), the installation
safety requirements for overcurrent
protection.
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Occupational Safety and Health Admin., Labor
(c) Test instruments and equipment—(1)
Use. Only qualified persons may perform testing work on electric circuits
or equipment.
(2) Visual inspection. Test instruments
and equipment and all associated test
leads, cables, power cords, probes, and
connectors shall be visually inspected
for external defects and damage before
the equipment is used. If there is a defect or evidence of damage that might
expose an employee to injury, the defective or damaged item shall be removed from service, and no employee
may use it until repairs and tests necessary to render the equipment safe
have been made.
(3) Rating of equipment. Test instruments and equipment and their accessories shall be rated for the circuits
and equipment to which they will be
connected and shall be designed for the
environment in which they will be
used.
(d) Occasional use of flammable or ignitible materials. Where flammable materials are present only occasionally,
electric equipment capable of igniting
them shall not be used, unless measures are taken to prevent hazardous
conditions from developing. Such materials include, but are not limited to:
flammable gases, vapors, or liquids;
combustible dust; and ignitible fibers
or flyings.
NOTE: Electrical installation requirements
for locations where flammable materials are
present on a regular basis are contained in
§ 1910.307.
[55 FR 32019, Aug. 6, 1990]
§ 1910.335 Safeguards
protection.
for
personnel
(a) Use of protective equipment—(1)
Personal protective equipment. (i) Employees working in areas where there
are potential electrical hazards shall
be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the
body to be protected and for the work
to be performed.
rfrederick on PROD1PC67 with CFR
NOTE: Personal protective equipment requirements are contained in subpart I of this
part.
(ii) Protective equipment shall be
maintained in a safe, reliable condition
§ 1910.335
and shall be periodically inspected or
tested, as required by § 1910.137.
(iii) If the insulating capability of
protective equipment may be subject
to damage during use, the insulating
material shall be protected. (For example, an outer covering of leather is
sometimes used for the protection of
rubber insulating material.)
(iv) Employees shall wear nonconductive head protection wherever there is
a danger of head injury from electric
shock or burns due to contact with exposed energized parts.
(v) Employees shall wear protective
equipment for the eyes or face wherever there is danger of injury to the
eyes or face from electric arcs or
flashes or from flying objects resulting
from electrical explosion.
(2) General protective equipment and
tools. (i) When working near exposed
energized conductors or circuit parts,
each employee shall use insulated tools
or handling equipment if the tools or
handling equipment might make contact with such conductors or parts. If
the insulating capability of insulated
tools or handling equipment is subject
to damage, the insulating material
shall be protected.
(A) Fuse handling equipment, insulated for the circuit voltage, shall be
used to remove or install fuses when
the fuse terminals are energized.
(B) Ropes and handlines used near exposed energized parts shall be nonconductive.
(ii) Protective shields, protective
barriers, or insulating materials shall
be used to protect each employee from
shock, burns, or other electrically related injuries while that employee is
working near exposed energized parts
which might be accidentally contacted
or where dangerous electric heating or
arcing might occur. When normally enclosed live parts are exposed for maintenance or repair, they shall be guarded to protect unqualified persons from
contact with the live parts.
(b) Alerting techniques. The following
alerting techniques shall be used to
warn and protect employees from hazards which could cause injury due to
electric shock, burns, or failure of electric equipment parts:
(1) Safety signs and tags. Safety signs,
safety symbols, or accident prevention
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§§ 1910.336–1910.360
29 CFR Ch. XVII (7–1–07 Edition)
tags shall be used where necessary to
warn employees about electrical hazards which may endanger them, as required by § 1910.145.
(2) Barricades. Barricades shall be
used in conjunction with safety signs
where it is necessary to prevent or
limit employee access to work areas
exposing employees to uninsulated energized conductors or circuit parts.
Conductive barricades may not be used
where they might cause an electrical
contact hazard.
(3) Attendants. If signs and barricades
do not provide sufficient warning and
protection from electrical hazards, an
attendant shall be stationed to warn
and protect employees.
[55 FR 32020, Aug. 6, 1990]
§§ 1910.336–1910.360
[Reserved]
SAFETY-RELATED MAINTENANCE
REQUIREMENTS
§§ 1910.361–1910.380
[Reserved]
SAFETY REQUIREMENTS FOR SPECIAL
EQUIPMENT
§§ 1910.381–1910.398
[Reserved]
rfrederick on PROD1PC67 with CFR
DEFINITIONS
§ 1910.399 Definitions applicable to
this subpart.
Acceptable. An installation or equipment is acceptable to the Assistant
Secretary of Labor, and approved within the meaning of this Subpart S:
(i) If it is accepted, or certified, or
listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory; or
(ii) With respect to an installation or
equipment of a kind which no nationally recognized testing laboratory accepts, certifies, lists, labels, or determines to be safe, if it is inspected or
tested by another Federal agency, or
by a State, municipal, or other local
authority responsible for enforcing occupational safety provisions of the National Electrical Code and found in
compliance with the provisions of the
National Electrical Code as applied in
this subpart; or
(iii) With respect to custom-made
equipment or related installations
which are designed, fabricated for, and
intended for use by a particular customer, if it is determined to be safe for
its intended use by its manufacturer on
the basis of test data which the employer keeps and makes available for
inspection to the Assistant Secretary
and his authorized representatives.
Refer to § 1910.7 for definition of nationally recognized testing laboratory.
Accepted. An installation is ‘‘accepted’’ if it has been inspected and found
by a nationally recognized testing laboratory to conform to specified plans
or to procedures of applicable codes.
Accessible. (As applied to wiring
methods.) Capable of being removed or
exposed without damaging the building
structure or finish, or not permanently
closed in by the structure or finish of
the building. (See ‘‘concealed’’ and ‘‘exposed.’’)
Accessible. (As applied to equipment.)
Admitting close approach; not guarded
by locked doors, elevation, or other effective means. (See ‘‘Readily accessible.’’)
Ampacity. Current-carrying capacity
of electric conductors expressed in amperes.
Appliances. Utilization equipment,
generally other than industrial, normally built in standardized sizes or
types, which is installed or connected
as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying,
etc.
Approved. Acceptable to the authority enforcing this subpart. The authority enforcing this subpart is the Assistant Secretary of Labor for Occupational Safety and Health. The definition of ‘‘acceptable’’ indicates what is
acceptable to the Assistant Secretary
of Labor, and therefore approved within the meaning of this Subpart.
Approved for the purpose. Approved for
a specific purpose, environment, or application described in a particular
standard requirement.
Suitability of equipment or materials for a specific purpose, environment or application may be determined
by a nationally recognized testing laboratory, inspection agency or other organization concerned with product
evaluation as part of its listing and labeling program. (See ‘‘Labeled’’ or
‘‘Listed.’’)
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Armored cable. Type AC armored
cable is a fabricated assembly of insulated conductors in a flexible metallic
enclosure.
Askarel. A generic term for a group of
nonflammable synthetic chlorinated
hydrocarbons used as electrical insulating media. Askarels of various
compositional types are used. Under
arcing conditions the gases produced,
while consisting predominantly of noncombustible hydrogen chloride, can include varying amounts of combustible
gases depending upon the askarel type.
Attachment plug (Plug cap) (Cap). A
device which, by insertion in a receptacle, establishes connection between
the conductors of the attached flexible
cord and the conductors connected permanently to the receptacle.
Automatic. Self-acting, operating by
its own mechanism when actuated by
some impersonal influence, as, for example, a change in current strength,
pressure, temperature, or mechanical
configuration.
Bare conductor. See ‘‘Conductor.’’
Bonding. The permanent joining of
metallic parts to form an electrically
conductive path which will assure electrical continuity and the capacity to
conduct safely any current likely to be
imposed.
Bonding jumper. A reliable conductor
to assure the required electrical conductivity between metal parts required
to be electrically connected.
Branch circuit. The circuit conductors
between the final overcurrent device
protecting the circuit and the outlet(s).
Building. A structure which stands
alone or which is cut off from adjoining
structures by fire walls with all openings therein protected by approved fire
doors.
Cabinet. An enclosure designed either
for surface or flush mounting, and provided with a frame, mat, or trim in
which a swinging door or doors are or
may be hung.
Cable tray system. A cable tray system
is a unit or assembly of units or sections, and associated fittings, made of
metal or other noncombustible materials forming a rigid structural system
used to support cables. Cable tray systems include ladders, troughs, channels, solid bottom trays, and other
similar structures.
§ 1910.399
Cablebus. Cablebus is an approved assembly of insulated conductors with
fittings and conductor terminations in
a completely enclosed, ventilated, protective metal housing.
Center pivot irrigation machine. A center pivot irrigation machine is a multimotored irrigation machine which revolves around a central pivot and employs alignment switches or similar devices to control individual motors.
Certified. Equipment is ‘‘certified’’ if
it (a) has been tested and found by a
nationally recognized testing laboratory to meet nationally recognized
standards or to be safe for use in a
specified manner, or (b) is of a kind
whose production is periodically inspected by a nationally recognized
testing laboratory, and (c) it bears a
label, tag, or other record of certification.
Circuit breaker. (i) (600 volts nominal,
or less). A device designed to open and
close a circuit by nonautomatic means
and to open the circuit automatically
on a predetermined overcurrent without injury to itself when properly applied within its rating.
(ii) (Over 600 volts, nominal). A
switching device capable of making,
carrying, and breaking currents under
normal circuit conditions, and also
making, carrying for a specified time,
and breaking currents under specified
abnormal circuit conditions, such as
those of short circuit.
Class I locations. Class I locations are
those in which flammable gases or vapors are or may be present in the air in
quantities sufficient to produce explosive or ignitible mixtures. Class I locations include the following:
(i) Class I, Division 1. A Class I, Division 1 location is a location: (a) in
which hazardous concentrations of
flammable gases or vapors may exist
under normal operating conditions; or
(b) in which hazardous concentrations
of such gases or vapors may exist frequently because of repair or maintenance operations or because of leakage;
or (c) in which breakdown or faulty operation of equipment or processes
might release hazardous concentrations of flammable gases or vapors, and
might also cause simultaneous failure
of electric equipment.
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§ 1910.399
29 CFR Ch. XVII (7–1–07 Edition)
NOTE: This classification usually includes
locations where volatile flammable liquids
or liquefied flammable gases are transferred
from one container to another; interiors of
spray booths and areas in the vicinity of
spraying and painting operations where volatile flammable solvents are used; locations
containing open tanks or vats of volatile
flammable liquids; drying rooms or compartments for the evaporation of flammable solvents; locations containing fat and oil extraction equipment using volatile flammable
solvents; portions of cleaning and dyeing
plants where flammable liquids are used; gas
generator rooms and other portions of gas
manufacturing plants where flammable gas
may escape; inadequately ventilated pump
rooms for flammable gas or for volatile flammable liquids; the interiors of refrigerators
and freezers in which volatile flammable materials are stored in open, lightly stoppered,
or easily ruptured containers; and all other
locations where ignitible concentrations of
flammable vapors or gases are likely to
occur in the course of normal operations.
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(ii) Class I, Division 2. A Class I, Division 2 location is a location: (a) in
which volatile flammable liquids or
flammable gases are handled, processed, or used, but in which the hazardous liquids, vapors, or gases will
normally be confined within closed
containers or closed systems from
which they can escape only in case of
accidental rupture or breakdown of
such containers or systems, or in case
of abnormal operation of equipment; or
(b) in which hazardous concentrations
of gases or vapors are normally prevented by positive mechanical ventilation, and which might become hazardous through failure or abnormal operations of the ventilating equipment;
or (c) that is adjacent to a Class I, Division 1 location, and to which hazardous
concentrations of gases or vapors
might occasionally be communicated
unless such communication is prevented by adequate positive-pressure
ventilation from a source of clean air,
and effective safeguards against ventilation failure are provided.
NOTE: This classification usually includes
locations where volatile flammable liquids
or flammable gases or vapors are used, but
which would become hazardous only in case
of an accident or of some unusual operating
condition. The quantity of flammable material that might escape in case of accident,
the adequacy of ventilating equipment, the
total area involved, and the record of the industry or business with respect to explosions
or fires are all factors that merit consideration in determining the classification and
extent of each location.
Piping without valves, checks, meters, and
similar devices would not ordinarily introduce a hazardous condition even though used
for flammable liquids or gases. Locations
used for the storage of flammable liquids or
a liquefied or compressed gases in sealed
containers would not normally be considered
hazardous unless also subject to other hazardous conditions.
Electrical conduits and their associated
enclosures separated from process fluids by a
single seal or barrier are classed as a Division 2 location if the outside of the conduit
and enclosures is a nonhazardous location.
Class II locations. Class II locations
are those that are hazardous because of
the presence of combustible dust. Class
II locations include the following:
(i) Class II, Division 1. A Class II, Division 1 location is a location: (a) In
which combustible dust is or may be in
suspension in the air under normal operating conditions, in quantities sufficient to produce explosive or ignitible
mixtures; or (b) where mechanical failure or abnormal operation of machinery or equipment might cause such explosive or ignitible mixtures to be produced, and might also provide a source
of ignition through simultaneous failure of electric equipment, operation of
protection devices, or from other
causes, or (c) in which combustible
dusts of an electrically conductive nature may be present.
NOTE: This classification may include
areas of grain handling and processing
plants, starch plants, sugar-pulverizing
plants, malting plants, hay-grinding plants,
coal pulverizing plants, areas where metal
dusts and powders are produced or processed,
and other similar locations which contain
dust producing machinery and equipment
(except where the equipment is dust-tight or
vented to the outside). These areas would
have combustible dust in the air, under normal operating conditions, in quantities sufficient to produce explosive or ignitible mixtures. Combustible dusts which are electrically nonconductive include dusts produced in the handling and processing of grain
and grain products, pulverized sugar and
cocoa, dried egg and milk powders, pulverized spices, starch and pastes, potato and
woodflour, oil meal from beans and seed,
dried hay, and other organic materials which
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Occupational Safety and Health Admin., Labor
may produce combustible dusts when processed or handled. Dusts containing magnesium or aluminum are particularly hazardous and the use of extreme caution is necessary to avoid ignition and explosion.
(ii) Class II, Division 2. A Class II, Division 2 location is a location in which:
(a) combustible dust will not normally
be in suspension in the air in quantities sufficient to produce explosive or
ignitible mixtures, and dust accumulations are normally insufficient to
interfere with the normal operation of
electrical equipment or other apparatus; or (b) dust may be in suspension
in the air as a result of infrequent malfunctioning of handling or processing
equipment, and dust accumulations resulting therefrom may be ignitible by
abnormal operation or failure of electrical equipment or other apparatus.
NOTE: This classification includes locations where dangerous concentrations of suspended dust would not be likely but where
dust accumulations might form on or in the
vicinity of electric equipment. These areas
may contain equipment from which appreciable quantities of dust would escape under
abnormal operating conditions or be adjacent to a Class II Division 1 location, as described above, into which an explosive or ignitible concentration of dust may be put into
suspension under abnormal operating conditions.
rfrederick on PROD1PC67 with CFR
Class III locations. Class III locations
are those that are hazardous because of
the presence of easily ignitible fibers
or flyings but in which such fibers or
flyings are not likely to be in suspension in the air in quantities sufficient
to produce ignitible mixtures. Class III
locations include the following:
(i) Class III, Division 1. A Class III, Division 1 location is a location in which
easily ignitible fibers or materials producing combustible flyings are handled, manufactured, or used.
NOTE: Such locations usually include some
parts of rayon, cotton, and other textile
mills; combustible fiber manufacturing and
processing plants; cotton gins and cottonseed mills; flax-processing plants; clothing
manufacturing plants; woodworking plants,
and establishments; and industries involving
similar hazardous processes or conditions.
Easily ignitible fibers and flyings include
rayon, cotton (including cotton linters and
cotton waste), sisal or henequen, istle, jute,
hemp, tow, cocoa fiber, oakum, baled waste
kapok, Spanish moss, excelsior, and other
materials of similar nature.
§ 1910.399
(ii) Class III, Division 2. A Class III,
Division 2 location is a location in
which easily ignitible fibers are stored
or handled, except in process of manufacture.
Collector ring. A collector ring is an
assembly of slip rings for transferring
electrical energy from a stationary to
a rotating member.
Concealed. Rendered inaccessible by
the structure or finish of the building.
Wires in concealed raceways are considered concealed, even though they
may become accessible by withdrawing
them. [See Accessible. (As applied to
wiring methods.)]
Conductor. (i) Bare. A conductor having no covering or electrical insulation
whatsoever.
(ii) Covered. A conductor encased
within material of composition or
thickness that is not recognized as
electrical insulation.
(iii) Insulated. A conductor encased
within material of composition and
thickness that is recognized as electrical insulation.
Conduit body. A separate portion of a
conduit or tubing system that provides
access through a removable cover(s) to
the interior of the system at a junction
of two or more sections of the system
or at a terminal point of the system.
Boxes such as FS and FD or larger cast
or sheet metal boxes are not classified
as conduit bodies.
Controller. A device or group of devices that serves to govern, in some
predetermined manner, the electric
power delivered to the apparatus to
which it is connected.
Cooking unit, counter-mounted. A
cooking appliance designed for mounting in or on a counter and consisting of
one or more heating elements, internal
wiring, and built-in or separately
mountable controls. (See Oven, wallmounted.)
Covered conductor. See Conductor.
Cutout. (Over 600 volts, nominal.) An
assembly of a fuse support with either
a fuseholder, fuse carrier, or disconnecting blade. The fuseholder or
fuse carrier may include a conducting
element (fuse link), or may act as the
disconnecting blade by the inclusion of
a nonfusible member.
Cutout box. An enclosure designed for
surface mounting and having swinging
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§ 1910.399
29 CFR Ch. XVII (7–1–07 Edition)
doors or covers secured directly to and
telescoping with the walls of the box
proper. (See Cabinet.)
Damp location. See Location.
Dead front. Without live parts exposed to a person on the operating side
of the equipment.
Device. A unit of an electrical system
which is intended to carry but not utilize electric energy.
Dielectric heating. Dielectric heating
is the heating of a nominally insulating material due to its own dielectric losses when the material is placed
in a varying electric field.
Disconnecting means. A device, or
group of devices, or other means by
which the conductors of a circuit can
be disconnected from their source of
supply.
Disconnecting (or Isolating) switch.
(Over 600 volts, nominal.) A mechanical
switching device used for isolating a
circuit or equipment from a source of
power.
Dry location. See Location.
Electric sign. A fixed, stationary, or
portable self-contained, electrically illuminated utilization equipment with
words or symbols designed to convey
information or attract attention.
Enclosed. Surrounded by a case, housing, fence or walls which will prevent
persons from accidentally contacting
energized parts.
Enclosure. The case or housing of apparatus, or the fence or walls surrounding an installation to prevent
personnel from accidentally contacting
energized parts, or to protect the
equipment from physical damage.
Equipment. A general term including
material, fittings, devices, appliances,
fixtures, apparatus, and the like, used
as a part of, or in connection with, an
electrical installation.
Equipment grounding conductor. See
Grounding conductor, equipment.
Explosion-proof apparatus. Apparatus
enclosed in a case that is capable of
withstanding an explosion of a specified gas or vapor which may occur
within it and of preventing the ignition
of a specified gas or vapor surrounding
the enclosure by sparks, flashes, or explosion of the gas or vapor within, and
which operates at such an external
temperature that it will not ignite a
surrounding flammable atmosphere.
Exposed. (As applied to live parts.)
Capable of being inadvertently touched
or approached nearer than a safe distance by a person. It is applied to parts
not suitably guarded, isolated, or insulated. (See Accessible. and Concealed.)
Exposed. (As applied to wiring methods.) On or attached to the surface or
behind panels designed to allow access.
[See Accessible. (As applied to wiring
methods.)]
Exposed.
(For
the
purposes
of
§ 1910.308(e), Communications systems.)
Where the circuit is in such a position
that in case of failure of supports or insulation, contact with another circuit
may result.
Externally operable. Capable of being
operated without exposing the operator
to contact with live parts.
Feeder. All circuit conductors between the service equipment, or the
generator switchboard of an isolated
plant, and the final branch-circuit
overcurrent device.
Fitting. An accessory such as a locknut, bushing, or other part of a wiring
system that is intended primarily to
perform a mechanical rather than an
electrical function.
Fuse. (Over 600 volts, nominal.) An
overcurrent protective device with a
circuit opening fusible part that is
heated and severed by the passage of
overcurrent through it. A fuse comprises all the parts that form a unit capable of performing the prescribed
functions. It may or may not be the
complete device necessary to connect
it into an electrical circuit.
Ground. A conducting connection,
whether intentional or accidental, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the
earth.
Grounded. Connected to earth or to
some conducting body that serves in
place of the earth.
Grounded, effectively. (Over 600 volts,
nominal.) Permanently connected to
earth through a ground connection of
sufficiently low impedance and having
sufficient ampacity that ground fault
current which may occur cannot build
up to voltages dangerous to personnel.
Grounded conductor. A system or circuit conductor that is intentionally
grounded.
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Grounding conductor. A conductor
used to connect equipment or the
grounded circuit of a wiring system to
a grounding electrode or electrodes.
Grounding conductor, equipment. The
conductor used to connect the non-current-carrying metal parts of equipment, raceways, and other enclosures
to the system grounded conductor and/
or the grounding electrode conductor
at the service equipment or at the
source of a separately derived system.
Grounding electrode conductor. The
conductor used to connect the grounding electrode to the equipment grounding conductor and/or to the grounded
conductor of the circuit at the service
equipment or at the source of a separately derived system.
Ground-fault circuit-interrupter. A device whose function is to interrupt the
electric circuit to the load when a fault
current to ground exceeds some predetermined value that is less than that
required to operate the overcurrent
protective device of the supply circuit.
Guarded. Covered, shielded, fenced,
enclosed, or otherwise protected by
means of suitable covers, casings, barriers, rails, screens, mats, or platforms
to remove the likelihood of approach
to a point of danger or contact by persons or objects.
Health care facilities. Buildings or portions of buildings and mobile homes
that contain, but are not limited to,
hospitals, nursing homes, extended
care facilities, clinics, and medical and
dental offices, whether fixed or mobile.
Heating equipment. For the purposes
of § 1910.306(g), the term heating equipment includes any equipment used for
heating purposes if heat is generated
by induction or dielectric methods.
Hoistway. Any shaftway, hatchway,
well hole, or other vertical opening or
space in which an elevator or dumbwaiter is designed to operate.
Identified. Identified, as used in reference to a conductor or its terminal,
means that such conductor or terminal
can be readily recognized as grounded.
Induction heating. Induction heating
is the heating of a nominally conductive material due to its own I2R losses
when the material is placed in a varying electromagnetic field.
Insulated conductor. See Conductor.
§ 1910.399
Interrupter switch. (Over 600 volts,
nominal.) A switch capable of making,
carrying, and interrupting specified
currents.
Irrigation machine. An irrigation machine is an electrically driven or controlled machine, with one or more motors, not hand portable, and used primarily to transport and distribute
water for agricultural purposes.
Isolated. Not readily accessible to
persons unless special means for access
are used.
Isolated power system. A system comprising an isolating transformer or its
equivalent, a line isolation monitor,
and its ungrounded circuit conductors.
Labeled. Equipment is labeled if there
is attached to it a label, symbol, or
other identifying mark of a nationally
recognized testing laboratory which,
(a) makes periodic inspections of the
production of such equipment, and (b)
whose labeling indicates compliance
with nationally recognized standards
or tests to determine safe use in a specified manner.
Lighting outlet. An outlet intended for
the direct connection of a lampholder,
a lighting fixture, or a pendant cord
terminating in a lampholder.
Line-clearance tree trimming. The
pruning, trimming, repairing, maintaining, removing, or clearing of trees
or cutting of brush that is within 10
feet (305 cm) of electric supply lines
and equipment.
Listed. Equipment is listed if it is of a
kind mentioned in a list which, (a) is
published by a nationally recognized
laboratory which makes periodic inspection of the production of such
equipment, and (b) states such equipment meets nationally recognized
standards or has been tested and found
safe for use in a specified manner.
Location—(i) Damp location. Partially
protected locations under canopies,
marquees, roofed open porches, and
like locations, and interior locations
subject to moderate degrees of moisture, such as some basements, some
barns, and some cold-storage warehouses.
(ii) Dry location. A location not normally subject to dampness or wetness.
A location classified as dry may be
temporarily subject to dampness or
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wetness, as in the case of a building
under construction.
(iii) Wet location. Installations underground or in concrete slabs or masonry
in direct contact with the earth, and
locations subject to saturation with
water or other liquids, such as vehiclewashing areas, and locations exposed
to weather and unprotected.
May. If a discretionary right, privilege, or power is conferred, the word
‘‘may’’ is used. If a right, privilege, or
power is abridged or if an obligation to
abstain from acting is imposed, the
word ‘‘may’’ is used with a restrictive
‘‘no,’’ ‘‘not,’’ or ‘‘only.’’ (E.g., no employer may . . . ; an employer may not
. . . ; only qualified persons may. . . .)
Medium voltage cable. Type MV medium voltage cable is a single or multiconductor solid dielectric insulated
cable rated 2000 volts or higher.
Metal-clad cable. Type MC cable is a
factory assembly of one or more conductors, each individually insulated
and enclosed in a metallic sheath of
interlocking tape, or a smooth or corrugated tube.
Mineral-insulated metal-sheathed cable.
Type MI mineral-insulated metalsheathed cable is a factory assembly of
one or more conductors insulated with
a highly compressed refractory mineral
insulation and enclosed in a liquidtight
and gastight continuous copper sheath.
Mobile
X-ray.
X-ray
equipment
mounted on a permanent base with
wheels and/or casters for moving while
completely assembled.
Nonmetallic-sheathed
cable.
Nonmetallic-sheathed cable is a factory assembly of two or more insulated conductors having an outer sheath of
moisture resistant, flame-retardant,
nonmetallic
material.
Nonmetallic
sheathed cable is manufactured in the
following types:
(i) Type NM. The overall covering has
a flame-retardant and moisture-resistant finish.
(ii) Type NMC. The overall covering
is flame-retardant, moisture-resistant,
fungus-resistant, and corrosion-resistant.
Oil (filled) cutout. (Over 600 volts,
nominal.) A cutout in which all or part
of the fuse support and its fuse link or
disconnecting blade are mounted in oil
with complete immersion of the con-
tacts and the fusible portion of the
conducting element (fuse link), so that
arc interruption by severing of the fuse
link or by opening of the contacts will
occur under oil.
Open wiring on insulators. Open wiring
on insulators is an exposed wiring
method using cleats, knobs, tubes, and
flexible tubing for the protection and
support of single insulated conductors
run in or on buildings, and not concealed by the building structure.
Outlet. A point on the wiring system
at which current is taken to supply
utilization equipment.
Outline lighting. An arrangement of
incandescent lamps or electric discharge tubing to outline or call attention to certain features such as the
shape of a building or the decoration of
a window.
Oven, wall-mounted. An oven for
cooking purposes designed for mounting in or on a wall or other surface and
consisting of one of more heating elements, internal wiring, and built-in or
separately mountable controls. (See
Cooking unit, counter-mounted.)
Overcurrent. Any current in excess of
the rated current of equipment or the
ampacity of a conductor. It may result
from overload (see definition), short
circuit, or ground fault. A current in
excess of rating may be accommodated
by certain equipment and conductors
for a given set of conditions. Hence the
rules for overcurrent protection are
specific for particular situations.
Overload. Operation of equipment in
excess of normal, full load rating, or of
a conductor in excess of rated
ampacity which, when it persists for a
sufficient length of time, would cause
damage or dangerous overheating. A
fault, such as a short circuit or ground
fault, is not an overload. (See Overcurrent.)
Panelboard. A single panel or group of
panel units designed for assembly in
the form of a single panel; including
buses, automatic overcurrent devices,
and with or without switches for the
control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against
a wall or partition and accessible only
from the front. (See Switchboard.)
Permanently installed decorative fountains and reflection pools. Those that are
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constructed in the ground, on the
ground, or in a building in such a manner that the pool cannot be readily disassembled for storage and are served by
electrical circuits of any nature. These
units are primarily constructed for
their aesthetic value and not intended
for swimming or wading.
Permanently installed swimming pools,
wading and therapeutic pools. Those
that are constructed in the ground, on
the ground, or in a building in such a
manner that the pool cannot be readily
disassembled for storage whether or
not served by electrical circuits of any
nature.
Portable X-ray. X-ray equipment designed to be hand-carried.
Power and control tray cable. Type TC
power and control tray cable is a factory assembly of two or more insulated
conductors, with or without associated
bare or covered grounding conductors
under a nonmetallic sheath, approved
for installation in cable trays, in raceways, or where supported by a messenger wire.
Power fuse. (Over 600 volts, nominal.)
See Fuse.
Power-limited tray cable. Type PLTC
nonmetallic-sheathed power limited
tray cable is a factory assembly of two
or more insulated conductors under a
nonmetallic jacket.
Power outlet. An enclosed assembly
which may include receptacles, circuit
breakers, fuseholders, fused switches,
buses and watt-hour meter mounting
means; intended to supply and control
power to mobile homes, recreational
vehicles or boats, or to serve as a
means for distributing power required
to operate mobile or temporarily installed equipment.
Premises wiring system. That interior
and exterior wiring, including power,
lighting, control, and signal circuit
wiring together with all of its associated hardware, fittings, and wiring devices, both permanently and temporarily installed, which extends from
the load end of the service drop, or load
end of the service lateral conductors to
the outlet(s). Such wiring does not include wiring internal to appliances, fixtures, motors, controllers, motor control centers, and similar equipment.
§ 1910.399
Qualified person. One familiar with
the construction and operation of the
equipment and the hazards involved.
NOTE 1: Whether an employee is considered
to be a ‘‘qualified person’’ will depend upon
various circumstances in the workplace. It is
possible and, in fact, likely for an individual
to be considered ‘‘qualified’’ with regard to
certain equipment in the workplace, but
‘‘unqualified’’ as to other equipment. (See
§ 1910.332(b)(3) for training requirements that
specifically apply to qualified persons.)
NOTE 2: An employee who is undergoing onthe-job training and who, in the course of
such training, has demonstrated an ability
to perform duties safely at his or her level of
training and who is under the direct supervision of a qualified person is considered to
be a qualified person for the performance of
those duties.
Raceway. A channel designed expressly for holding wires, cables, or
busbars, with additional functions as
permitted in this subpart. Raceways
may be of metal or insulating material,
and the term includes rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight
flexible metal conduit, flexible metallic tubing, flexible metal conduit, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways,
cellular metal floor raceways, surface
raceways, wireways, and busways.
Readily accessible. Capable of being
reached quickly for operation, renewal,
or inspections, without requiring those
to whom ready access is requisite to
climb over or remove obstacles or to
resort to portable ladders, chairs, etc.
(See Accessible.)
Receptacle. A receptacle is a contact
device installed at the outlet for the
connection of a single attachment
plug. A single receptacle is a single
contact device with no other contact
device on the same yoke. A multiple
receptacle is a single device containing
two or more receptacles.
Receptacle outlet. An outlet where one
or more receptacles are installed.
Remote-control circuit. Any electric
circuit that controls any other circuit
through a relay or an equivalent device.
Sealable equipment. Equipment enclosed in a case or cabinet that is provided with a means of sealing or locking so that live parts cannot be made
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accessible without opening the enclosure. The equipment may or may not
be operable without opening the enclosure.
Separately derived system. A premises
wiring system whose power is derived
from generator, transformer, or converter winding and has no direct electrical connection, including a solidly
connected grounded circuit conductor,
to supply conductors originating in another system.
Service. The conductors and equipment for delivering energy from the
electricity supply system to the wiring
system of the premises served.
Service cable. Service conductors
made up in the form of a cable.
Service conductors. The supply conductors that extend from the street
main or from transformers to the service equipment of the premises supplied.
Service drop. The overhead service
conductors from the last pole or other
aerial support to and including the
splices, if any, connecting to the service-entrance conductors at the building
or other structure.
Service-entrance
cable.
Service-entrance cable is a single conductor or
multiconductor
assembly
provided
with or without an overall covering,
primarily used for services and of the
following types:
(i) Type SE, having a flame-retardant,
moisture-resistant covering, but not
required to have inherent protection
against mechanical abuse.
(ii) Type USE, recognized for underground use, having a moisture-resistant covering, but not required to have
a flame-retardant covering or inherent
protection against mechanical abuse.
Single-conductor cables having an insulation specifically approved for the
purpose do not require an outer covering.
Service-entrance conductors, overhead
system. The service conductors between
the terminals of the service equipment
and a point usually outside the building, clear of building walls, where
joined by tap or splice to the service
drop.
Service entrance conductors, underground system. The service conductors
between the terminals of the service
equipment and the point of connection
to the service lateral. Where service
equipment is located outside the building walls, there may be no service-entrance conductors, or they may be entirely outside the building.
Service equipment. The necessary
equipment, usually consisting of a circuit breaker or switch and fuses, and
their accessories, located near the
point of entrance of supply conductors
to a building or other structure, or an
otherwise defined area, and intended to
consititute the main control and
means of cutoff of the supply.
Service raceway. The raceway that encloses the service-entrance conductors.
Shielded nonmetallic-sheathed cable.
Type SNM, shielded nonmetallicsheathed cable is a factory assembly of
two or more insulated conductors in an
extruded core of moisture-resistant,
flame-resistant nonmetallic material,
covered with an overlapping spiral
metal tape and wire shield and jacketed with an extruded moisture-,
flame-, oil-, corrosion-, fungus-, and
sunlight-resistant nonmetallic material.
Show window. Any window used or designed to be used for the display of
goods or advertising material, whether
it is fully or partly enclosed or entirely
open at the rear and whether or not it
has a platform raised higher than the
street floor level.
Sign. See Electric sign.
Signaling circuit. Any electric circuit
that energizes signaling equipment.
Special permission. The written consent of the authority having jurisdiction.
Storable swimming or wading pool. A
pool with a maximum dimension of 15
feet and a maximum wall height of 3
feet and is so constructed that it may
be readily disassembled for storage and
reassembled to its original integrity.
Switchboard. A large single panel,
frame, or assembly of panels which
have switches, buses, instruments,
overcurrent and other protective devices mounted on the face or back or
both. Switchboards are generally accessible from the rear as well as from
the front and are not intended to be installed in cabinets. (See Panelboard.)
Switches.
(i) General-use switch. A switch intended for use in general distribution
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and branch circuits. It is rated in amperes, and it is capable of interrupting
its rated current at its rated voltage.
(ii) General-use snap switch. A form of
general-use switch so constructed that
it can be installed in flush device boxes
or on outlet box covers, or otherwise
used in conjunction with wiring systems recognized by this subpart.
(iii) Isolating switch. A switch intended for isolating an electric circuit
from the source of power. It has no interrupting rating, and it is intended to
be operated only after the circuit has
been opened by some other means.
(iv) Motor-circuit switch. A switch,
rated in horsepower, capable of interrupting the maximum operating overload current of a motor of the same
horsepower rating as the switch at the
rated voltage.
Switching devices. (Over 600 volts,
nominal.) Devices designed to close
and/or open one or more electric circuits. Included in this category are circuit breakers, cutouts, disconnecting
(or isolating) switches, disconnecting
means, interrupter switches, and oil
(filled) cutouts.
Transportable X-ray. X-ray equipment
installed in a vehicle or that may readily be disassembled for transport in a
vehicle.
Utilization
equipment.
Utilization
equipment means equipment which utilizes electric energy for mechanical,
chemical, heating, lighting, or similar
useful purpose.
Utilization system. A utilization system is a system which provides electric
power and light for employee workplaces, and includes the premises wiring system and utilization equipment.
Ventilated. Provided with a means to
permit circulation of air sufficient to
remove an excess of heat, fumes, or vapors.
Volatile flammable liquid. A flammable
liquid having a flash point below 38 degrees C (100 degrees F) or whose temperature is above its flash point.
Voltage (of a circuit). The greatest
root-mean-square (effective) difference
of potential between any two conductors of the circuit concerned.
Voltage, nominal. A nominal value assigned to a circuit or system for the
purpose of conveniently designating its
voltage class (as 120/240, 480Y/277, 600,
§ 1910.399
etc.). The actual voltage at which a circuit operates can vary from the nominal within a range that permits satisfactory operation of equipment.
Voltage to ground. For grounded circuits, the voltage between the given
conductor and that point or conductor
of the circuit that is grounded; for
ungrounded circuits, the greatest voltage between the given conductor and
any other conductor of the circuit.
Watertight. So constructed that moisture will not enter the enclosure.
Weatherproof. So constructed or protected that exposure to the weather
will not interfere with successful operation. Rainproof, raintight, or watertight equipment can fulfill the requirements for weatherproof where varying
weather conditions other than wetness,
such as snow, ice, dust, or temperature
extremes, are not a factor.
Wet location. See Location.
Wireways. Wireways are sheet-metal
troughs with hinged or removable covers for housing and protecting electric
wires and cable and in which conductors are laid in place after the wireway
has been installed as a complete system.
[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7,
1981, as amended at 53 FR 12123, Apr. 12, 1988;
55 FR 32020, Aug. 6, 1990; 55 FR 46054, Nov. 1,
1990]
EFFECTIVE DATE NOTE: At 72 FR 7215, Feb.
14, 2007, § 1910.399 was revised, effective Aug.
13, 2007. For the convenience of the user, the
revised text is set forth as follows:
§ 1910.399
part.
Definitions applicable to this sub-
Acceptable. An installation or equipment is
acceptable to the Assistant Secretary of
Labor, and approved within the meaning of
this Subpart S:
(1) If it is accepted, or certified, or listed,
or labeled, or otherwise determined to be
safe by a nationally recognized testing laboratory recognized pursuant to § 1910.7; or
(2) With respect to an installation or equipment of a kind that no nationally recognized
testing laboratory accepts, certifies, lists,
labels, or determines to be safe, if it is inspected or tested by another Federal agency,
or by a State, municipal, or other local authority responsible for enforcing occupational safety provisions of the National Electrical Code, and found in compliance with
the provisions of the National Electrical
Code as applied in this subpart; or
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29 CFR Ch. XVII (7–1–07 Edition)
(3) With respect to custom-made equipment or related installations that are designed, fabricated for, and intended for use
by a particular customer, if it is determined
to be safe for its intended use by its manufacturer on the basis of test data which the
employer keeps and makes available for inspection to the Assistant Secretary and his
authorized representatives.
Accepted. An installation is ‘‘accepted’’ if it
has been inspected and found by a nationally
recognized testing laboratory to conform to
specified plans or to procedures of applicable
codes.
Accessible. (As applied to wiring methods.)
Capable of being removed or exposed without
damaging the building structure or finish, or
not permanently closed in by the structure
or finish of the building. (See ‘‘concealed’’
and ‘‘exposed.’’)
Accessible. (As applied to equipment.) Admitting close approach; not guarded by
locked doors, elevation, or other effective
means. (See ‘‘Readily accessible.’’)
Ampacity. The current, in amperes, that a
conductor can carry continuously under the
conditions of use without exceeding its temperature rating.
Appliances. Utilization equipment, generally other than industrial, normally built
in standardized sizes or types, that is installed or connected as a unit to perform one
or more functions.
Approved. Acceptable to the authority enforcing this subpart. The authority enforcing
this subpart is the Assistant Secretary of
Labor for Occupational Safety and Health.
The definition of ‘‘acceptable’’ indicates
what is acceptable to the Assistant Secretary of Labor, and therefore approved
within the meaning of this subpart.
Armored cable (Type AC). A fabricated assembly of insulated conductors in a flexible
metallic enclosure.
Askarel. A generic term for a group of nonflammable synthetic chlorinated hydrocarbons used as electrical insulating media.
Askarels of various compositional types are
used. Under arcing conditions, the gases produced, while consisting predominantly of
noncombustible hydrogen chloride, can include varying amounts of combustible gases
depending upon the askarel type.
Attachment plug (Plug cap)(Cap). A device
that, by insertion in a receptacle, establishes
a connection between the conductors of the
attached flexible cord and the conductors
connected permanently to the receptacle.
Automatic. Self-acting, operating by its
own mechanism when actuated by some impersonal influence, as, for example, a change
in current strength, pressure, temperature,
or mechanical configuration.
Bare conductor. See Conductor.
Barrier. A physical obstruction that is intended to prevent contact with equipment or
live parts or to prevent unauthorized access
to a work area.
Bathroom. An area including a basin with
one or more of the following: a toilet, a tub,
or a shower.
Bonding (Bonded). The permanent joining
of metallic parts to form an electrically conductive path that ensures electrical continuity and the capacity to conduct safely
any current likely to be imposed.
Bonding jumper. A conductor that assures
the necessary electrical conductivity between metal parts required to be electrically
connected.
Branch circuit. The circuit conductors between the final overcurrent device protecting the circuit and the outlets.
Building. A structure that stands alone or
is cut off from adjoining structures by fire
walls with all openings therein protected by
approved fire doors.
Cabinet. An enclosure designed either for
surface or flush mounting, and provided with
a frame, mat, or trim in which a swinging
door or doors are or can be hung.
Cable tray system. A unit or assembly of
units or sections and associated fittings
forming a rigid structural system used to securely fasten or support cables and raceways. Cable tray systems include ladders,
troughs, channels, solid bottom trays, and
other similar structures.
Cablebus. An assembly of insulated conductors with fittings and conductor terminations in a completely enclosed, ventilated,
protective metal housing.
Cell line. An assembly of electrically interconnected electrolytic cells supplied by a
source of direct current power.
Cell line attachments and auxiliary equipment. Cell line attachments and auxiliary
equipment include, but are not limited to,
auxiliary tanks, process piping, ductwork,
structural supports, exposed cell line conductors, conduits and other raceways, pumps,
positioning equipment, and cell cutout or bypass electrical devices. Auxiliary equipment
also includes tools, welding machines, crucibles, and other portable equipment used for
operation and maintenance within the electrolytic cell line working zone. In the cell
line working zone, auxiliary equipment includes the exposed conductive surfaces of
ungrounded cranes and crane-mounted cellservicing equipment.
Center pivot irrigation machine. A multi-motored irrigation machine that revolves
around a central pivot and employs alignment switches or similar devices to control
individual motors.
Certified. Equipment is ‘‘certified’’ if it
bears a label, tag, or other record of certification that the equipment:
(1) Has been tested and found by a nationally recognized testing laboratory to meet
nationally recognized standards or to be safe
for use in a specified manner; or
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(2) Is of a kind whose production is periodically inspected by a nationally recognized
testing laboratory and is accepted by the
laboratory as safe for its intended use.
Circuit breaker. A device designed to open
and close a circuit by nonautomatic means
and to open the circuit automatically on a
predetermined overcurrent without damage
to itself when properly applied within its
rating.
Class I locations. Class I locations are those
in which flammable gases or vapors are or
may be present in the air in quantities sufficient to produce explosive or ignitable mixtures. Class I locations include the following:
(1) Class I, Division 1. A Class I, Division 1
location is a location:
(i) In which ignitable concentrations of
flammable gases or vapors may exist under
normal operating conditions; or
(ii) In which ignitable concentrations of
such gases or vapors may exist frequently
because of repair or maintenance operations
or because of leakage; or
(iii) In which breakdown or faulty operation of equipment or processes might release ignitable concentrations of flammable
gases or vapors, and might also cause simultaneous failure of electric equipment.
NOTE TO THE DEFINITION OF ‘‘CLASS I, DIVISION 1:’’ This classification usually includes
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locations where volatile flammable liquids
or liquefied flammable gases are transferred
from one container to another; interiors of
spray booths and areas in the vicinity of
spraying and painting operations where volatile flammable solvents are used; locations
containing open tanks or vats of volatile
flammable liquids; drying rooms or compartments for the evaporation of flammable solvents; locations containing fat and oil extraction equipment using volatile flammable
solvents; portions of cleaning and dyeing
plants where flammable liquids are used; gas
generator rooms and other portions of gas
manufacturing plants where flammable gas
may escape; inadequately ventilated pump
rooms for flammable gas or for volatile flammable liquids; the interiors of refrigerators
and freezers in which volatile flammable materials are stored in open, lightly stoppered,
or easily ruptured containers; and all other
locations where ignitable concentrations of
flammable vapors or gases are likely to
occur in the course of normal operations.
(2) Class I, Division 2. A Class I, Division 2
location is a location:
(i) In which volatile flammable liquids or
flammable gases are handled, processed, or
used, but in which the hazardous liquids, vapors, or gases will normally be confined
within closed containers or closed systems
from which they can escape only in the event
of accidental rupture or breakdown of such
containers or systems, or as a result of abnormal operation of equipment; or
§ 1910.399
(ii) In which ignitable concentrations of
gases or vapors are normally prevented by
positive mechanical ventilation, and which
might become hazardous through failure or
abnormal operations of the ventilating
equipment; or
(iii) That is adjacent to a Class I, Division
1 location, and to which ignitable concentrations of gases or vapors might occasionally
be communicated unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air,
and effective safeguards against ventilation
failure are provided.
NOTE TO THE DEFINITION OF ‘‘CLASS I, DIVISION 2:’’ This classification usually includes
locations where volatile flammable liquids
or flammable gases or vapors are used, but
which would become hazardous only in case
of an accident or of some unusual operating
condition. The quantity of flammable material that might escape in case of accident,
the adequacy of ventilating equipment, the
total area involved, and the record of the industry or business with respect to explosions
or fires are all factors that merit consideration in determining the classification and
extent of each location.
Piping without valves, checks, meters, and
similar devices would not ordinarily introduce a hazardous condition even though used
for flammable liquids or gases. Locations
used for the storage of flammable liquids or
liquefied or compressed gases in sealed containers would not normally be considered
hazardous unless also subject to other hazardous conditions.
Electrical conduits and their associated
enclosures separated from process fluids by a
single seal or barrier are classed as a Division 2 location if the outside of the conduit
and enclosures is a nonhazardous location.
(3) Class I, Zone 0. A Class I, Zone 0 location is a location in which one of the following conditions exists:
(i) Ignitable concentrations of flammable
gases or vapors are present continuously; or
(ii) Ignitable concentrations of flammable
gases or vapors are present for long periods
of time.
NOTE TO THE DEFINITION OF ‘‘CLASS I, ZONE
0:’’ As a guide in determining when flammable gases or vapors are present continuously or for long periods of time, refer to
Recommended Practice for Classification of Locations for Electrical Installations of Petroleum
Facilities Classified as Class I, Zone 0, Zone 1 or
Zone 2, API RP 505–1997; Electrical Apparatus
for Explosive Gas Atmospheres, Classifications
of Hazardous Areas, IEC 79–10–1995; Area Classification Code for Petroleum Installations,
Model Code—Part 15, Institute for Petroleum;
and Electrical Apparatus for Explosive Gas
Atmospheres, Classifications of Hazardous
(Classified) Locations, ISA S12.24.01–1997.
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(4) Class I, Zone 1. A Class I, Zone 1 location is a location in which one of the following conditions exists:
(i) Ignitable concentrations of flammable
gases or vapors are likely to exist under normal operating conditions; or
(ii) Ignitable concentrations of flammable
gases or vapors may exist frequently because
of repair or maintenance operations or because of leakage; or
(iii) Equipment is operated or processes are
carried on of such a nature that equipment
breakdown or faulty operations could result
in the release of ignitable concentrations of
flammable gases or vapors and also cause simultaneous failure of electric equipment in
a manner that would cause the electric
equipment to become a source of ignition; or
(iv) A location that is adjacent to a Class
I, Zone 0 location from which ignitable concentrations of vapors could be communicated, unless communication is prevented
by adequate positive pressure ventilation
from a source of clean air and effective safeguards against ventilation failure are provided.
(5) Class I, Zone 2. A Class I, Zone 2 location is a location in which one of the following conditions exists:
(i) Ignitable concentrations of flammable
gases or vapors are not likely to occur in
normal operation and if they do occur will
exist only for a short period; or
(ii) Volatile flammable liquids, flammable
gases, or flammable vapors are handled,
processed, or used, but in which the liquids,
gases, or vapors are normally confined within closed containers or closed systems from
which they can escape only as a result of accidental rupture or breakdown of the containers or system or as the result of the abnormal operation of the equipment with
which the liquids or gases are handled, processed, or used; or
(iii) Ignitable concentrations of flammable
gases or vapors normally are prevented by
positive mechanical ventilation, but which
may become hazardous as the result of failure or abnormal operation of the ventilation
equipment; or
(iv) A location that is adjacent to a Class
I, Zone 1 location, from which ignitable concentrations of flammable gases or vapors
could be communicated, unless such communication is prevented by adequate positivepressure ventilation from a source of clean
air, and effective safeguards against ventilation failure are provided.
Class II locations. Class II locations are
those that are hazardous because of the presence of combustible dust. Class II locations
include the following:
(1) Class II, Division 1. A Class II, Division
1 location is a location:
(i) In which combustible dust is or may be
in suspension in the air under normal oper-
ating conditions, in quantities sufficient to
produce explosive or ignitable mixtures; or
(ii) Where mechanical failure or abnormal
operation of machinery or equipment might
cause such explosive or ignitable mixtures to
be produced, and might also provide a source
of ignition through simultaneous failure of
electric equipment, through operation of
protection devices, or from other causes; or
(iii) In which combustible dusts of an electrically conductive nature may be present.
NOTE TO THE DEFINITION OF ‘‘CLASS
SION 1:’’ This classification may
II, DIVIinclude
areas of grain handling and processing
plants, starch plants, sugar-pulverizing
plants, malting plants, hay-grinding plants,
coal pulverizing plants, areas where metal
dusts and powders are produced or processed,
and other similar locations that contain dust
producing machinery and equipment (except
where the equipment is dust-tight or vented
to the outside). These areas would have combustible dust in the air, under normal operating conditions, in quantities sufficient to
produce explosive or ignitable mixtures.
Combustible dusts that are electrically nonconductive include dusts produced in the
handling and processing of grain and grain
products, pulverized sugar and cocoa, dried
egg and milk powders, pulverized spices,
starch and pastes, potato and wood flour, oil
meal from beans and seed, dried hay, and
other organic materials which may produce
combustible dusts when processed or handled. Dusts containing magnesium or aluminum are particularly hazardous, and the
use of extreme caution is necessary to avoid
ignition and explosion.
(2) Class II, Division 2. A Class II, Division
2 location is a location where:
(i) Combustible dust will not normally be
in suspension in the air in quantities sufficient to produce explosive or ignitable mixtures, and dust accumulations will normally
be insufficient to interfere with the normal
operation of electric equipment or other apparatus, but combustible dust may be in suspension in the air as a result of infrequent
malfunctioning of handling or processing
equipment; and
(ii) Resulting combustible dust accumulations on, in, or in the vicinity of the electric
equipment may be sufficient to interfere
with the safe dissipation of heat from electric equipment or may be ignitable by abnormal operation or failure of electric equipment.
NOTE TO THE DEFINITION OF ‘‘CLASS II, DIVISION 2:’’ This classification includes locations where dangerous concentrations of suspended dust would not be likely, but where
dust accumulations might form on or in the
vicinity of electric equipment. These areas
may contain equipment from which appreciable quantities of dust would escape under
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abnormal operating conditions or be adjacent to a Class II Division 1 location, as described above, into which an explosive or ignitable concentration of dust may be put
into suspension under abnormal operating
conditions.
Class III locations. Class III locations are
those that are hazardous because of the presence of easily ignitable fibers or flyings, but
in which such fibers or flyings are not likely
to be in suspension in the air in quantities
sufficient to produce ignitable mixtures.
Class III locations include the following:
(1) Class III, Division 1. A Class III, Division
1 location is a location in which easily ignitable fibers or materials producing combustible flyings are handled, manufactured, or
used.
III, DIinclude
some parts of rayon, cotton, and other textile mills; combustible fiber manufacturing
and processing plants; cotton gins and cotton-seed mills; flax-processing plants; clothing manufacturing plants; woodworking
plants, and establishments; and industries
involving similar hazardous processes or conditions.
Easily ignitable fibers and flyings include
rayon, cotton (including cotton linters and
cotton waste), sisal or henequen, istle, jute,
hemp, tow, cocoa fiber, oakum, baled waste
kapok, Spanish moss, excelsior, and other
materials of similar nature.
rfrederick on PROD1PC67 with CFR
NOTE TO THE DEFINITION OF ‘‘CLASS
VISION 1:’’ Such locations usually
(2) Class III, Division 2. A Class III, Division
2 location is a location in which easily ignitable fibers are stored or handled, other than
in the process of manufacture.
Collector ring. An assembly of slip rings for
transferring electric energy from a stationary to a rotating member.
Competent Person. One who is capable of
identifying existing and predictable hazards
in the surroundings or working conditions
that are unsanitary, hazardous, or dangerous
to employees and who has authorization to
take prompt corrective measures to eliminate them.
Concealed. Rendered inaccessible by the
structure or finish of the building. Wires in
concealed raceways are considered concealed, even though they may become accessible by withdrawing them. (See Accessible.
(As applied to wiring methods.))
Conductor—(1) Bare. A conductor having no
covering or electrical insulation whatsoever.
(2) Covered. A conductor encased within
material of composition or thickness that is
not recognized by this subpart as electrical
insulation.
(3) Insulated. A conductor encased within
material of composition and thickness that
is recognized by this subpart as electrical insulation.
Conduit body. A separate portion of a conduit or tubing system that provides access
§ 1910.399
through one or more removable covers to the
interior of the system at a junction of two or
more sections of the system or at a terminal
point of the system. Boxes such as FS and
FD or larger cast or sheet metal boxes are
not classified as conduit bodies.
Controller. A device or group of devices that
serves to govern, in some predetermined
manner, the electric power delivered to the
apparatus to which it is connected.
Covered conductor. See Conductor.
Cutout. (Over 600 volts, nominal.) An assembly of a fuse support with either a
fuseholder, fuse carrier, or disconnecting
blade. The fuseholder or fuse carrier may include a conducting element (fuse link), or
may act as the disconnecting blade by the
inclusion of a nonfusible member.
Cutout box. An enclosure designed for surface mounting and having swinging doors or
covers secured directly to and telescoping
with the walls of the box proper. (See Cabinet.)
Damp location. See Location.
Dead front. Without live parts exposed to a
person on the operating side of the equipment
Deenergized. Free from any electrical connection to a source of potential difference
and from electrical charge; not having a potential different from that of the earth.
Device. A unit of an electrical system that
is intended to carry but not utilize electric
energy.
Dielectric heating. The heating of a nominally insulating material due to its own dielectric losses when the material is placed in
a varying electric field.
Disconnecting means. A device, or group of
devices, or other means by which the conductors of a circuit can be disconnected from
their source of supply.
Disconnecting (or Isolating) switch. (Over 600
volts, nominal.) A mechanical switching device used for isolating a circuit or equipment
from a source of power.
Electrolytic cell line working zone. The cell
line working zone is the space envelope
wherein operation or maintenance is normally performed on or in the vicinity of exposed energized surfaces of electrolytic cell
lines or their attachments.
Electrolytic cells. A tank or vat in which
electrochemical reactions are caused by applying energy for the purpose of refining or
producing usable materials.
Enclosed. Surrounded by a case, housing,
fence, or walls that will prevent persons
from accidentally contacting energized
parts.
Enclosure. The case or housing of apparatus, or the fence or walls surrounding an
installation to prevent personnel from accidentally contacting energized parts, or to
protect the equipment from physical damage.
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§ 1910.399
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Energized. Electrically connected to a
source of potential difference.
Equipment. A general term including material, fittings, devices, appliances, fixtures,
apparatus, and the like, used as a part of, or
in connection with, an electrical installation.
Equipment
grounding
conductor.
See
Grounding conductor, equipment.
Explosion-proof apparatus. Apparatus enclosed in a case that is capable of withstanding an explosion of a specified gas or
vapor that may occur within it and of preventing the ignition of a specified gas or
vapor surrounding the enclosure by sparks,
flashes, or explosion of the gas or vapor
within, and that operates at such an external
temperature that it will not ignite a surrounding flammable atmosphere.
Exposed. (As applied to live parts.) Capable
of being inadvertently touched or approached nearer than a safe distance by a
person. It is applied to parts not suitably
guarded, isolated, or insulated. (See Accessible and Concealed.)
Exposed. (As applied to wiring methods.) On
or attached to the surface, or behind panels
designed to allow access. (See Accessible. (As
applied to wiring methods.))
Exposed. (For the purposes of § 1910.308(e).)
Where the circuit is in such a position that
in case of failure of supports or insulation,
contact with another circuit may result.
Externally operable. Capable of being operated without exposing the operator to contact with live parts.
Feeder. All circuit conductors between the
service equipment, the source of a separate
derived system, or other power supply source
and the final branch-circuit overcurrent device.
Fitting. An accessory such as a locknut,
bushing, or other part of a wiring system
that is intended primarily to perform a mechanical rather than an electrical function.
Fountain. Fountains, ornamental pools,
display pools, and reflection pools.
NOTE TO THE DEFINITION OF ‘‘FOUNTAIN:’’
This definition does not include drinking
fountains.
Fuse. (Over 600 volts, nominal.) An overcurrent protective device with a circuit opening
fusible part that is heated and severed by the
passage of overcurrent through it. A fuse
comprises all the parts that form a unit capable of performing the prescribed functions.
It may or may not be the complete device
necessary to connect it into an electrical circuit.
Ground. A conducting connection, whether
intentional or accidental, between an electric circuit or equipment and the earth, or to
some conducting body that serves in place of
the earth.
Grounded. Connected to the earth or to
some conducting body that serves in place of
the earth.
Grounded, effectively. Intentionally connected to earth through a ground connection
or connections of sufficiently low impedance
and having sufficient current-carrying capacity to prevent the buildup of voltages
that may result in undue hazards to connected equipment or to persons.
Grounded conductor. A system or circuit
conductor that is intentionally grounded.
Grounding conductor. A conductor used to
connect equipment or the grounded circuit of
a wiring system to a grounding electrode or
electrodes.
Grounding conductor, equipment. The conductor used to connect the noncurrent-carrying metal parts of equipment, raceways,
and other enclosures to the system grounded
conductor, the grounding electrode conductor, or both, at the service equipment or
at the source of a separately derived system.
Grounding electrode conductor. The conductor used to connect the grounding electrode to the equipment grounding conductor,
to the grounded conductor, or to both, of the
circuits at the service equipment or at the
source of a separately derived system.
Ground-fault circuit-interrupter. A device intended for the protection of personnel that
functions to deenergize a circuit or a portion
of a circuit within an established period of
time when a current to ground exceeds some
predetermined value that is less than that
required to operate the overcurrent protective device of the supply circuit.
Guarded. Covered, shielded, fenced, enclosed, or otherwise protected by means of
suitable covers, casings, barriers, rails,
screens, mats, or platforms to remove the
likelihood of approach to a point of danger
or contact by persons or objects.
Health care facilities. Buildings or portions
of buildings in which medical, dental, psychiatric, nursing, obstetrical, or surgical
care are provided.
NOTE TO THE DEFINITION OF ‘‘HEALTH CARE
FACILITIES:’’ Health care facilities include,
but are not limited to, hospitals, nursing
homes, limited care facilities, clinics, medical and dental offices, and ambulatory care
centers, whether permanent or movable.
Heating equipment. For the purposes of
§ 1910.306(g), the term ‘‘heating equipment’’
includes any equipment used for heating purposes if heat is generated by induction or dielectric methods.
Hoistway. Any shaftway, hatchway, well
hole, or other vertical opening or space that
is designed for the operation of an elevator
or dumbwaiter.
Identified (as applied to equipment). Approved as suitable for the specific purpose,
function, use, environment, or application,
where described in a particular requirement.
NOTE TO THE DEFINITION OF ‘‘IDENTIFIED:’’
Some examples of ways to determine suitability of equipment for a specific purpose,
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environment, or application include investigations by a nationally recognized testing
laboratory (through listing and labeling), inspection agency, or other organization recognized under the definition of ‘‘acceptable.’’
Induction heating. The heating of a nominally conductive material due to its own I2R
losses when the material is placed in a varying electromagnetic field.
Insulated. Separated from other conducting
surfaces by a dielectric (including air space)
offering a high resistance to the passage of
current.
Insulated conductor. See Conductor, Insulated.
Interrupter switch. (Over 600 volts, nominal.)
A switch capable of making, carrying, and
interrupting specified currents.
Irrigation Machine. An electrically driven
or controlled machine, with one or more motors, not hand portable, and used primarily
to transport and distribute water for agricultural purposes.
Isolated. (As applied to location.) Not readily
accessible to persons unless special means
for access are used.
Isolated power system. A system comprising
an isolating transformer or its equivalent, a
line isolation monitor, and its ungrounded
circuit conductors.
Labeled. Equipment is ‘‘labeled’’ if there is
attached to it a label, symbol, or other identifying mark of a nationally recognized testing laboratory:
(1) That makes periodic inspections of the
production of such equipment, and
(2) Whose labeling indicates compliance
with nationally recognized standards or tests
to determine safe use in a specified manner.
Lighting outlet. An outlet intended for the
direct connection of a lampholder, a lighting
fixture, or a pendant cord terminating in a
lampholder.
Line-clearance tree trimming. The pruning,
trimming, repairing, maintaining, removing,
or clearing of trees or cutting of brush that
is within 305 cm (10 ft) of electric supply
lines and equipment.
Listed. Equipment is ‘‘listed’’ if it is of a
kind mentioned in a list that:
(1) Is published by a nationally recognized
laboratory that makes periodic inspection of
the production of such equipment, and
(2) States that such equipment meets nationally recognized standards or has been
tested and found safe for use in a specified
manner.
Live parts. Energized conductive components.
Location—(1) Damp location. Partially protected locations under canopies, marquees,
roofed open porches, and like locations, and
interior locations subject to moderate degrees of moisture, such as some basements,
some barns, and some cold-storage warehouses.
§ 1910.399
(2) Dry location. A location not normally
subject to dampness or wetness. A location
classified as dry may be temporarily subject
to dampness or wetness, as in the case of a
building under construction.
(3) Wet location. Installations underground
or in concrete slabs or masonry in direct
contact with the earth, and locations subject
to saturation with water or other liquids,
such as vehicle-washing areas, and locations
unprotected and exposed to weather.
Medium voltage cable (Type MV). A single or
multiconductor solid dielectric insulated
cable rated 2001 volts or higher.
Metal-clad cable (Type MC). A factory assembly of one or more insulated circuit conductors with or without optical fiber members enclosed in an armor of interlocking
metal tape, or a smooth or corrugated metallic sheath.
Mineral-insulated metal-sheathed cable (Type
MI). Type MI, mineral-insulated metalsheathed, cable is a factory assembly of one
or more conductors insulated with a highly
compressed refractory mineral insulation
and enclosed in a liquidtight and gastight
continuous copper or alloy steel sheath.
Mobile X-ray. X-ray equipment mounted on
a permanent base with wheels or casters or
both for moving while completely assembled.
Motor control center. An assembly of one or
more enclosed sections having a common
power bus and principally containing motor
control units.
Nonmetallic-sheathed cable (Types NM, NMC,
and NMS). A factory assembly of two or more
insulated conductors having an outer sheath
of moisture resistant, flame-retardant, nonmetallic material.
Oil (filled) cutout. (Over 600 volts, nominal.)
A cutout in which all or part of the fuse support and its fuse link or disconnecting blade
are mounted in oil with complete immersion
of the contacts and the fusible portion of the
conducting element (fuse link), so that arc
interruption by severing of the fuse link or
by opening of the contacts will occur under
oil.
Open wiring on insulators. Open wiring on
insulators is an exposed wiring method using
cleats, knobs, tubes, and flexible tubing for
the protection and support of single insulated conductors run in or on buildings, and
not concealed by the building structure.
Outlet. A point on the wiring system at
which current is taken to supply utilization
equipment.
Outline lighting. An arrangement of incandescent lamps or electric discharge lighting
to outline or call attention to certain features, such as the shape of a building or the
decoration of a window.
Overcurrent. Any current in excess of the
rated current of equipment or the ampacity
of a conductor. It may result from overload,
short circuit, or ground fault.
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Overhaul means to perform a major replacement, modification, repair, or rehabilitation similar to that involved when a new
building or facility is built, a new wing is
added, or an entire floor is renovated.
Overload. Operation of equipment in excess
of normal, full-load rating, or of a conductor
in excess of rated ampacity that, when it
persists for a sufficient length of time, would
cause damage or dangerous overheating. A
fault, such as a short circuit or ground fault,
is not an overload. (See Overcurrent.)
Panelboard. A single panel or group of
panel units designed for assembly in the
form of a single panel; including buses, automatic overcurrent devices, and with or without switches for the control of light, heat, or
power circuits; designed to be placed in a
cabinet or cutout box placed in or against a
wall or partition and accessible only from
the front. (See Switchboard.)
Permanently installed decorative fountains
and reflection pools. Pools that are constructed in the ground, on the ground, or in
a building in such a manner that the fountain or pool cannot be readily disassembled
for storage, whether or not served by electrical circuits of any nature. These units are
primarily constructed for their aesthetic
value and are not intended for swimming or
wading.
Permanently installed swimming, wading, and
therapeutic pools. Pools that are constructed
in the ground or partially in the ground, and
all other capable of holding water in a depth
greater than 1.07 m (42 in.). The definition
also applies to all pools installed inside of a
building, regardless of water depth, whether
or not served by electric circuits of any nature.
Portable X-ray. X-ray equipment designed
to be hand-carried.
Power and control tray cable (Type TC). A
factory assembly of two or more insulated
conductors, with or without associated bare
or covered grounding conductors under a
nonmetallic sheath, approved for installation in cable trays, in raceways, or where
supported by a messenger wire.
Power fuse. (Over 600 volts, nominal.) See
Fuse.
Power-limited tray cable (Type PLTC). A factory assembly of two or more insulated conductors under a nonmetallic jacket.
Power outlet. An enclosed assembly, which
may include receptacles, circuit breakers,
fuseholders, fused switches, buses, and watthour meter mounting means, that is intended to supply and control power to mobile
homes, recreational vehicles, or boats or to
serve as a means for distributing power needed to operate mobile or temporarily installed
equipment.
Premises wiring. (Premises wiring system.)
The interior and exterior wiring, including
power, lighting, control, and signal circuit
wiring together with all of their associated
hardware, fittings, and wiring devices, both
permanently and temporarily installed, that
extends from the service point of utility conductors or source of power (such as a battery, a solar photovoltaic system, or a generator, transformer, or converter) to the outlets. Such wiring does not include wiring internal to appliances, fixtures, motors, controllers, motor control centers, and similar
equipment.
Qualified person. One who has received
training in and has demonstrated skills and
knowledge in the construction and operation
of electric equipment and installations and
the hazards involved.
NOTE 1 TO THE DEFINITION OF ‘‘QUALIFIED
PERSON:’’ Whether an employee is considered
to be a ‘‘qualified person’’ will depend upon
various circumstances in the workplace. For
example, it is possible and, in fact, likely for
an individual to be considered ‘‘qualified’’
with regard to certain equipment in the
workplace, but ‘‘unqualified’’ as to other
equipment. (See 1910.332(b)(3) for training requirements that specifically apply to qualified persons.)
NOTE 2 TO THE DEFINITION OF ‘‘QUALIFIED
PERSON:’’ An employee who is undergoing onthe-job training and who, in the course of
such training, has demonstrated an ability
to perform duties safely at his or her level of
training and who is under the direct supervision of a qualified person is considered to
be a qualified person for the performance of
those duties.
Raceway. An enclosed channel of metal or
nonmetallic materials designed expressly for
holding wires, cables, or busbars, with additional functions as permitted in this standard. Raceways include, but are not limited
to, rigid metal conduit, rigid nonmetallic
conduit,
intermediate
metal
conduit,
liquidtight flexible conduit, flexible metallic
tubing, flexible metal conduit, electrical metallic tubing, electrical nonmetallic tubing,
underfloor raceways, cellular concrete floor
raceways, cellular metal floor raceways, surface raceways, wireways, and busways.
Readily accessible. Capable of being reached
quickly for operation, renewal, or inspections, so that those needing ready access do
not have to climb over or remove obstacles
or to resort to portable ladders, chairs, etc.
(See Accessible.)
Receptacle. A receptacle is a contact device
installed at the outlet for the connection of
an attachment plug. A single receptacle is a
single contact device with no other contact
device on the same yoke. A multiple receptacle is two or more contact devices on the
same yoke.
Receptacle outlet. An outlet where one or
more receptacles are installed.
Remote-control circuit. Any electric circuit
that controls any other circuit through a
relay or an equivalent device.
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Sealable equipment. Equipment enclosed in
a case or cabinet that is provided with a
means of sealing or locking so that live parts
cannot be made accessible without opening
the enclosure. The equipment may or may
not be operable without opening the enclosure.
Separately derived system. A premises wiring
system whose power is derived from a battery, a solar photovoltaic system, or from a
generator,
transformer,
or
converter
windings, and that has no direct electrical
connection, including a solidly connected
grounded circuit conductor, to supply conductors originating in another system.
Service. The conductors and equipment for
delivering electric energy from the serving
utility to the wiring system of the premises
served.
Service cable. Service conductors made up
in the form of a cable.
Service conductors. The conductors from the
service point to the service disconnecting
means.
Service drop. The overhead service conductors from the last pole or other aerial support to and including the splices, if any, connecting to the service-entrance conductors
at the building or other structure.
Service-entrance cable. A single conductor
or multiconductor assembly provided with or
without an overall covering, primarily used
for services, and is of the following types:
(1) Type SE. Type SE, having a flame-retardant, moisture resistant covering; and
(2) Type USE. Type USE, identified for underground use, having a moisture-resistant
covering, but not required to have a flameretardant covering. Cabled, single-conductor,
Type USE constructions recognized for underground use may have a bare copper conductor cabled with the assembly. Type USE
single, parallel, or cable conductor assemblies recognized for underground use may
have a bare copper concentric conductor applied. These constructions do not require an
outer overall covering.
Service-entrance conductors, overhead system.
The service conductors between the terminals of the service equipment and a point
usually outside the building, clear of building walls, where joined by tap or splice to
the service drop.
Service entrance conductors, underground
system. The service conductors between the
terminals of the service equipment and the
point of connection to the service lateral.
Service equipment. The necessary equipment, usually consisting of one or more circuit breakers or switches and fuses, and
their accessories, connected to the load end
of service conductors to a building or other
structure, or an otherwise designated area,
and intended to constitute the main control
and cutoff of the supply.
§ 1910.399
Service point. The point of connection between the facilities of the serving utility and
the premises wiring.
Shielded nonmetallic-sheathed cable (Type
SNM). A factory assembly of two or more insulated conductors in an extruded core of
moisture-resistant,
flame-resistant
nonmetallic material, covered with an overlapping spiral metal tape and wire shield and
jacketed with an extruded moisture-, flame, oil-, corrosion-, fungus-, and sunlight-resistant nonmetallic material.
Show window. Any window used or designed
to be used for the display of goods or advertising material, whether it is fully or partly
enclosed or entirely open at the rear and
whether or not it has a platform raised higher than the street floor level.
Signaling circuit. Any electric circuit that
energizes signaling equipment.
Storable swimming or wading pool. A pool
that is constructed on or above the ground
and is capable of holding water to a maximum depth of 1.07 m (42 in.), or a pool with
nonmetallic, molded polymeric walls or inflatable fabric walls regardless of dimension.
Switchboard. A large single panel, frame, or
assembly of panels on which are mounted, on
the face or back, or both, switches, overcurrent and other protective devices, buses, and
(usually) instruments. Switchboards are generally accessible from the rear as well as
from the front and are not intended to be installed in cabinets. (See Panelboard.)
Switch—(1) General-use switch. A switch intended for use in general distribution and
branch circuits. It is rated in amperes, and it
is capable of interrupting its rated current
at its rated voltage.
(2) General-use snap switch. A form of general-use switch constructed so that it can be
installed in device boxes or on box covers, or
otherwise used in conjunction with wiring
systems recognized by this subpart.
(3) Isolating switch. A switch intended for
isolating an electric circuit from the source
of power. It has no interrupting rating, and
it is intended to be operated only after the
circuit has been opened by some other
means.
(4) Motor-circuit switch. A switch, rated in
horsepower, capable of interrupting the maximum operating overload current of a motor
of the same horsepower rating as the switch
at the rated voltage.
Switching devices. (Over 600 volts, nominal.)
Devices designed to close and open one or
more electric circuits. Included in this category are circuit breakers, cutouts, disconnecting (or isolating) switches, disconnecting means, interrupter switches, and
oil (filled) cutouts.
Transportable X-ray. X-ray equipment installed in a vehicle or that may readily be
disassembled for transport in a vehicle.
Utilization equipment. Equipment that utilizes
electric
energy
for
electronic,
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Pt. 1910, Subpt. S, App. A
29 CFR Ch. XVII (7–1–07 Edition)
electromechanical, chemical, heating, lighting, or similar purposes.
Ventilated. Provided with a means to permit circulation of air sufficient to remove an
excess of heat, fumes, or vapors.
Volatile flammable liquid. A flammable liquid having a flash point below 38 °C (100 °F),
or a flammable liquid whose temperature is
above its flash point, or a Class II combustible liquid having a vapor pressure not exceeding 276 kPa (40 psia) at 38 °C (100 °F) and
whose temperature is above its flash point.
Voltage (of a circuit). The greatest rootmean-square (rms) (effective) difference of
potential between any two conductors of the
circuit concerned.
Voltage, nominal. A nominal value assigned
to a circuit or system for the purpose of conveniently designating its voltage class (as
120/240 volts, 480Y/277 volts, 600 volts). The
actual voltage at which a circuit operates
can vary from the nominal within a range
that permits satisfactory operation of equipment.
Voltage to ground. For grounded circuits,
the voltage between the given conductor and
that point or conductor of the circuit that is
grounded; for ungrounded circuits, the greatest voltage between the given conductor and
any other conductor of the circuit.
Watertight. So constructed that moisture
will not enter the enclosure.
Weatherproof. So constructed or protected
that exposure to the weather will not interfere with successful operation. Rainproof,
raintight, or watertight equipment can fulfill the requirements for weatherproof where
varying weather conditions other than wetness, such as snow, ice, dust, or temperature
extremes, are not a factor.
Wireways. Sheet-metal troughs with hinged
or removable covers for housing and protecting electric wires and cable and in which
conductors are laid in place after the
wireway has been installed as a complete
system.
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APPENDIX A TO SUBPART S OF PART
1910—REFERENCE DOCUMENTS
The following references provide information which can be helpful in understanding
and complying with the requirements contained in Subpart S:
ANSI A17.1–71 Safety Code for Elevators,
Dumbwaiters, Escalators and Moving
Walks.
ANSI B9.1–71 Safety Code for Mechanical
Refrigeration.
ANSI B30.2–76 Safety Code for Overhead and
Gantry Cranes.
ANSI B30.3–75 Hammerhead Tower Cranes.
ANSI B30.4–73 Safety Code for Portal,
Tower, and Pillar Cranes.
ANSI B30.5–68 Safety Code for Crawler, Locomotive, and Truck Cranes.
ANSI B30.6–77 Derricks.
ANSI B30.7–77 Base Mounted Drum Hoists.
ANSI B30.8–71 Safety Code for Floating
Cranes and Floating Derricks.
ANSI B30.11–73 Monorail Systems and
Underhung Cranes.
ANSI B30.12–75 Handling Loads Suspended
from Rotorcraft.
ANSI B30.13–77 Controlled Mechanical Storage Cranes.
ANSI B30.15–73 Safety Code for Mobile Hydraulic Cranes.
ANSI B30.16–73 Overhead Hoists.
ANSI C2–81 National Electrical Safety
Code.
ANSI C33.27–74 Safety Standard for Outlet
Boxes and Fittings for Use in Hazardous
Locations, Class I, Groups A, B, C, and D,
and Class II, Groups E, F, and G.
ANSI K61.1–72 Safety Requirements for the
Storage and Handling of Anhydrous Ammonia.
ASTM
D2155–66 Test
Method
for
Autoignition Temperature of Liquid Petroleum Products.
ASTM D3176–74 Method for Ultimate Analysis of Coal and Coke.
ASTM D3180–74 Method for Calculating Coal
and Coke Analyses from As Determined
to Different Bases.
IEEE 463–77 Standard for Electrical Safety
Practices in Electrolytic Cell Line Working Zones.
NFPA 20–76 Standard for the Installation of
Centrifugal Fire Pumps.
NFPA 30–78 Flammable and Combustible
Liquids Code.
NFPA 32–74 Standard for Drycleaning
Plants.
NFPA 33–73 Standard for Spray Application
Using Flammable and Combustible Materials.
NFPA 34–74 Standard for Dip Tanks Containing Flammable or Combustible Liquids.
NFPA 35–76 Standard for the Manufacture
of Organic Coatings.
NFPA 36–74 Standard for Solvent Extraction Plants.
NFPA 40–74 Standard for the Storage and
Handling of Cellulose Nitrate Motion
Picture Film.
NFPA 56A–73 Standard for the Use of Inhalation Anesthetics (Flammable and Nonflammable).
NFPA 56F–74 Standard for Nonflammable
Medical Gas Systems.
NFPA 58–76 Standard for the Storage and
Handling of Liquefied Petroleum Gases.
NFPA 59–76 Standard for the Storage and
Handling of Liquefied Petroleum Gases
at Utility Gas Plants.
NFPA 70–78 National Electrical Code.
NFPA 70C–74 Hazardous Locations Classification.
NFPA 70E Standard for the Electrical Safety Requirements for Employee Workplaces.
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Occupational Safety and Health Admin., Labor
NFPA 71–77 Standard for the Installation,
Maintenance, and Use of Central Station
Signaling Systems.
NFPA 72A–75 Standard for the Installation,
Maintenance, and Use of Local Protective Signaling Systems for Watchman,
Fire Alarm, and Supervisory Service.
NFPA 72B–75 Standard for the Installation,
Maintenance, and Use of Auxiliary Protective Signaling Systems for Fire
Alarm Service.
NFPA 72C–75 Standard for the Installation,
Maintenance, and Use of Remote Station
Protective Signaling Systems.
NFPA 72D–75 Standard for the Installation,
Maintenance, and Use of Proprietary
Protective Signaling Systems for Watchman, Fire Alarm, and Supervisory Service.
NFPA 72E–74 Standard for Automatic Fire
Detectors.
NFPA 74–75 Standard for Installation,
Maintenance, and Use of Household Fire
Warning Equipment.
NFPA 76A–73 Standard for Essential Electrical Systems for Health Care Facilities.
NFPA 77–72 Recommended Practice on
Static Electricity.
NFPA 80–77 Standard for Fire Doors and
Windows.
NFPA 86A–73 Standard for Ovens and Furnaces; Design, Location and Equipment.
NFPA 88A–73 Standard for Parking Structures.
NFPA 88B–73 Standard for Repair Garages.
NFPA 91–73 Standard for the Installation of
Blower and Exhaust Systems for Dust,
Stock, and Vapor Removal, or Conveying.
NFPA 101–78 Code for Safety to Life from
Fire in Buildings and Structures. (Life
Safety Code.)
NFPA 325M–69 Fire-Hazard Properties of
Flammable Liquids, Gases, and Volatile
Solids.
NFPA 493–75 Standard for Intrinsically Safe
Apparatus for Use in Class I Hazardous
Locations and Its Associated Apparatus.
NFPA 496–74 Standard for Purged and Pressurized Enclosures for Electrical Equipment in Hazardous Locations.
NFPA 497–75 Recommended Practice for
Classification of Class I Hazardous Locations for Electrical Installations in
Chemical Plants.
NFPA 505–75 Fire Safety Standard for Powered Industrial Trucks Including Type
Designations and Areas of Use.
NMAB 353–1–79 Matrix of Combustion-Relevant Properties and Classification of
Gases, Vapors, and Selected Solids.
NMAB 353–2–79 Test Equipment for Use in
Determining Classifications of Combustible Dusts.
Pt. 1910, Subpt. S, App. A
NMAB 353–3–80 Classification of Combustible Dusts in Accordance with the National Electrical Code.
[46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7,
1981]
EFFECTIVE DATE NOTE: At 72 FR 7221, Feb.
14, 2007, Appendix A was revised, effective
Aug. 13, 2007. For the convenience of the
user, the revised text is set forth as follows:
APPENDIX A—REFERENCES FOR FURTHER
INFORMATION
The references contained in this appendix
provide nonmandatory information that can
be helpful in understanding and complying
with Subpart S of this Part. However, compliance with these standards is not a substitute for compliance with Subpart S of this
Part.
ANSI/API RP 500–1998 (2002) Recommended
Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I Division 1 and Division 2.
ANSI/API RP 505–1997 (2002) Recommended
Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1 and Zone 2.
ANSI/ASME A17.1–2004 Safety Code for Elevators and Escalators.
ANSI/ASME B30.2–2005 Overhead and Gantry Cranes (Top Running Bridge, Single or Multiple Girder, Top Running Trolley Hoist).
ANSI/ASME B30.3–2004 Construction Tower
Cranes.
ANSI/ASME B30.4–2003 Portal, Tower, and
Pedestal Cranes.
ANSI/ASME B30.5–2004 Mobile And Locomotive Cranes.
ANSI/ASME B30.6–2003 Derricks.
ANSI/ASME B30.7–2001 Base Mounted Drum
Hoists.
ANSI/ASME B30.8–2004 Floating Cranes And
Floating Derricks.
ANSI/ASME B30.11–2004 Monorails And
Underhung Cranes.
ANSI/ASME B30.12–2001 Handling Loads
Suspended from Rotorcraft.
ANSI/ASME B30.13–2003 Storage/Retrieval (S/
R) Machines and Associated Equipment.
ANSI/ASME B30.16–2003 Overhead Hoists
(Underhung).
ANSI/ASME B30.22–2005 Articulating Boom
Cranes.
ANSI/ASSE Z244.1–2003 Control of Hazardous Energy Lockout/Tagout and Alternative
Methods.
ANSI/ASSE Z490.1–2001 Criteria for Accepted
Practices in Safety, Health, and Environmental
Training.
ANSI/IEEE C2–2002 National Electrical Safety Code.
ANSI K61.1–1999 Safety Requirements for the
Storage and Handling of Anhydrous Ammonia.
ANSI/UL 913–2003 Intrinsically Safe Apparatus and Associated Apparatus for Use in Class
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§ 1910.401
29 CFR Ch. XVII (7–1–07 Edition)
I, II, and III, Division 1, Hazardous (Classified)
Locations.
ASTM D3176–1989 (2002) Standard Practice
for Ultimate Analysis of Coal and Coke.
ASTM D3180–1989 (2002) Standard Practice
for Calculating Coal and Coke Analyses from
As-Determined to Different Bases.
NFPA 20–2003 Standard for the Installation
of Stationary Pumps for Fire Protection.
NFPA 30–2003 Flammable and Combustible
Liquids Code.
NFPA 32–2004 Standard for Drycleaning
Plants.
NFPA 33–2003 Standard for Spray Application Using Flammable or Combustible Materials.
NFPA 34–2003 Standard for Dipping and
Coating Processes Using Flammable or Combustible Liquids.
NFPA 35–2005 Standard for the Manufacture
of Organic Coatings.
NFPA 36–2004 Standard for Solvent Extraction Plants.
NFPA 40–2001 Standard for the Storage and
Handling of Cellulose Nitrate Film.
NFPA 58–2004 Liquefied Petroleum Gas Code.
NFPA 59–2004 Utility LP-Gas Plant Code.
NFPA 70–2002 National Electrical Code. (See
also NFPA 70–2005.)
NFPA 70E–2000 Standard for Electrical Safety
Requirements for Employee Workplaces. (See
also NFPA 70E–2004.)
NFPA 77–2000 Recommended Practice on Static Electricity.
NFPA 80–1999 Standard for Fire Doors and
Fire Windows.
NFPA 88A–2002 Standard for Parking Structures.
NFPA 91–2004 Standard for Exhaust Systems
for Air Conveying of Vapors, Gases, Mists, and
Noncombustible Particulate Solids.
NFPA 101–2006 Life Safety Code.
NFPA 496–2003 Standard for Purged and
Pressurized Enclosures for Electrical Equipment.
NFPA 497–2004 Recommended Practice for the
Classification of Flammable Liquids, Gases, or
Vapors and of Hazardous (Classified) Locations
for Electrical Installations in Chemical Process
Areas.
NFPA 505–2006 Fire Safety Standard for Powered Industrial Trucks Including Type Designations, Areas of Use, Conversions, Maintenance,
and Operation.
NFPA 820–2003 Standard for Fire Protection
in Wastewater Treatment and Collection Facilities.
NMAB 353–1–1979 Matrix of Combustion-Relevant Properties and Classification of Gases,
Vapors, and Selected Solids.
NMAB 353–2–1979 Test Equipment for Use in
Determining Classifications of Combustible
Dusts.
NMAB 353–3–1980 Classification of Combustible Dust in Accordance with the National
Electrical Code.
APPENDIX B TO SUBPART S OF PART
1910—EXPLANATORY DATA [RESERVED]
EFFECTIVE DATE NOTE: At 72 FR 7221, Feb.
14, 2007, Appendix B was removed, effective
Aug. 13, 2007.
APPENDIX C TO SUBPART S OF PART
1910—TABLES, NOTES, AND CHARTS
[RESERVED]
PUBLISHED AT 72 FR 7221, FEBRUARY
14, 2007.
EFFECTIVE DATE NOTE: At 72 FR 7221, Feb.
14, 2007, Appendix C was removed, effective
Aug. 13, 2007.
Subpart T—Commercial Diving
Operations
AUTHORITY: Sections 4, 6, and 8 of the Occupational Safety and Health Act of 1970 (29
U.S.C. 653, 655, and 657); Sec. 107, Contract
Work Hours and Safety Standards Act (the
Construction Safety Act) (40 U.S.C. 333); Sec.
41, Longshore and Harbor Workers’ Compensation Act (33 U.S.C. 941); Secretary of
Labor’s Order No. 8–76 (41 FR 25059), 9–83 (48
FR 35736), 1–90 (55 FR 9033), 3–2000 (65 FR
50017), or 5–2002 (67 FR 65008) as applicable; 29
CFR part 1911.
SOURCE: 42 FR 37668, July 22, 1977, unless
otherwise noted.
GENERAL
§ 1910.401
Scope and application.
(a) Scope. (1) This subpart (standard)
applies to every place of employment
within the waters of the United States,
or within any State, the District of Columbia, the Commonwealth of Puerto
Rico, the Virgin Islands, American
Samoa, Guam, the Trust Territory of
the Pacific Islands, Wake Island, Johnston Island, the Canal Zone, or within
the Outer Continental Shelf lands as
defined in the Outer Continental Shelf
Lands Act (67 Stat. 462, 43 U.S.C. 1331),
where diving and related support operations are performed.
(2) This standard applies to diving
and related support operations conducted in connection with all types of
work and employments, including general industry, construction, ship repairing, shipbuilding, shipbreaking and
longshoring. However, this standard
does not apply to any diving operation:
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| File Type | application/pdf |
| File Title | Document |
| Subject | Extracted Pages |
| Author | U.S. Government Printing Office |
| File Modified | 2008-06-25 |
| File Created | 2007-08-10 |