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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; 76 FR 80740, Dec. 27, 2011]
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]
DESIGN SAFETY STANDARDS FOR
ELECTRICAL SYSTEMS
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), 1–90 (55 FR 9033), 5–2002 (67 FR
65008), 5–2007 (72 FR 31160), as applicable; 29
CFR part 1911.
EFFECTIVE DATE NOTE: At 79 FR 20692, Apr.
11, 2014, the authority citation for subpart S
to part 1910 was revised, effective July 10,
2014. For the convenience of the user, the revised text is set forth as follows:
AUTHORITY: 29 U.S.C. 653, 655, 657; Secretary of Labor’s Order No. 8–76 (41 FR 25059),
1–90 (55 FR 9033), 5–2002 (67 FR 65008), 5–2007
(72 FR 31160), or 1–2012 (77 FR 3912), as applicable; and 29 CFR Part 1911.
SOURCE: 46 FR 4056, Jan. 16, 1981, unless
otherwise noted.
GENERAL
§ 1910.301
§ 1910.302
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
SOURCE: Sections 1910.302 through 1910.308
appear at 72 FR 7190, Feb. 14, 2007, unless otherwise noted.
§ 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 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
(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;
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§ 1910.302
29 CFR Ch. XVII (7–1–14 Edition)
(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
§ 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
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Occupational Safety and Health Admin., Labor
§ 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
§ 1910.304(b)(1)—Branch circuits—Identification of multiwire branch circuits
§ 1910.304(b)(3)(i)—Branch
circuits—
Ground-fault 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
§ 1910.303
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.
(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;
(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
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§ 1910.303
29 CFR Ch. XVII (7–1–14 Edition)
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 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 masonry, 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
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Occupational Safety and Health Admin., Labor
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
§ 1910.303
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.’’
(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
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§ 1910.303
29 CFR Ch. XVII (7–1–14 Edition)
(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.
(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.
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
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.
(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
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Occupational Safety and Health Admin., Labor
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
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
§ 1910.303
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 otherwise 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 (1-ft) or more extension
utilizing three or more strands of
barbed wire or equivalent.
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§ 1910.303
29 CFR Ch. XVII (7–1–14 Edition)
(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 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.
(5) Working space and guarding. (i) 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
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31
Occupational Safety and Health Admin., Labor
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 highvoltage 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:
§ 1910.303
(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.
‘‘DANGER—HIGH VOLTAGE—KEEP
OUT.’’
NOTE TO PARAGRAPH
TION: Piping and other
(h)(5)(vi) OF THIS SECfacilities are not considered foreign if provided for fire protection
of the electrical installation.
(iv) Illumination shall be provided
for all working spaces about electric
equipment.
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.
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31
§ 1910.304
29 CFR Ch. XVII (7–1–14 Edition)
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 2.8
ft
......................
2.8 ........................
2.8 + 9.5 mm/kV
over 35 kV.
1 9.0.
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.
[46 FR 4056, Jan. 16, 1981, as amended at 73
FR 64205, Oct. 29, 2008]
§ 1910.304
tion.
Wiring design and protec-
(a) Use and identification of grounded
and grounding conductors—(1) Identification of conductors. (i) A conductor used
as a grounded conductor shall be identifiable and distinguishable from all
other conductors.
(ii) 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) Identification
of multiwire branch circuits. Where more
than one nominal voltage system exists in a building containing multiwire
branch circuits, each ungrounded conductor of a multiwire branch circuit,
where accessible, shall be identified by
phase and system. The means of identification shall be permanently posted at
each branch-circuit panelboard.
(2) Receptacles and cord connectors. (i)
Receptacles installed on 15- and 20-ampere branch circuits shall be of the
grounding type except as permitted for
replacement receptacles in paragraph
(b)(2)(iv) of this section. Groundingtype receptacles shall be installed only
on circuits of the voltage class and current for which they are rated, except as
provided in Table S–4 and Table S–5.
(ii) Receptacles and cord connectors
having grounding contacts shall have
those contacts effectively grounded except for receptacles mounted on portable and vehicle-mounted generators in
accordance with paragraph (g)(3) of
this section and replacement receptacles installed in accordance with
paragraph (b)(2)(iv) of this section.
(iii) The grounding contacts of receptacles and cord connectors shall be
grounded by connection to the equipment grounding conductor of the circuit supplying the receptacle or cord
connector. The branch circuit wiring
method shall include or provide an
equipment grounding conductor to
which the grounding contacts of the receptacle or cord connector shall be
connected.
(iv) Replacement of receptacles shall
comply with the following requirements:
(A) Where a grounding means exists
in the receptacle enclosure or a
grounding conductor is installed,
grounding-type receptacles shall be
used and shall be connected to the
grounding means or conductor;
(B) Ground-fault circuit-interrupter
protected receptacles shall be provided
where replacements are made at receptacle outlets that are required to be so
protected elsewhere in this subpart;
and
(C) Where a grounding means does
not exist in the receptacle enclosure,
the installation shall comply with one
of the following provisions:
(1) A nongrounding-type receptacle
may be replaced with another nongrounding-type receptacle; or
(2) A nongrounding-type receptacle
may be replaced with a ground-fault
circuit-interrupter-type of receptacle
that is marked ‘‘No Equipment
Ground;’’ an equipment grounding conductor may not be connected from the
ground-fault
circuit-interrupter-type
receptacle to any outlet supplied from
the ground-fault circuit-interrupter receptacle; or
(3) A nongrounding-type receptacle
may be replaced with a grounding-type
receptacle where supplied through a
ground-fault circuit-interrupter; the
replacement
receptacle
shall
be
marked ‘‘GFCI Protected’’ and ‘‘No
Equipment Ground;’’ an equipment
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31
Occupational Safety and Health Admin., Labor
grounding conductor may not be connected to such grounding-type receptacles.
(v) Receptacles connected to circuits
having different voltages, frequencies,
or types of current (ac or dc) on the
same premises shall be of such design
that the attachment plugs used on
these circuits are not interchangeable.
(3) Ground-fault circuit interrupter protection for personnel. (i) All 125-volt, single-phase, 15- and 20-ampere receptacles installed in bathrooms or on
rooftops shall have ground-fault circuit-interrupter protection for personnel.
(ii) The following requirements apply
to temporary wiring installations that
are used during construction-like activities, including certain maintenance, remodeling, or repair activities,
involving buildings, structures or
equipment.
(A) All 125-volt, single-phase,15-, 20-,
and 30-ampere receptacle outlets that
are not part of the permanent wiring of
the building or structure and that are
in use by personnel shall have groundfault circuit-interrupter protection for
personnel.
NOTE 1 TO PARAGRAPH (b)(3)(ii)(A) OF THIS
SECTION: A cord connector on an extension
cord set is considered to be a receptacle outlet if the cord set is used for temporary electric power.
NOTE 2 TO PARAGRAPH (b)(3)(ii)(A) OF THIS
SECTION: Cord sets and devices incorporating
the required ground-fault circuit-interrupter
that are connected to the receptacle closest
to the source of power are acceptable forms
of protection.
(B) Receptacles other than 125 volt,
single-phase, 15-, 20-, and 30-ampere receptacles that are not part of the permanent wiring of the building or structure and that are in use by personnel
shall have ground-fault circuit-interrupter protection for personnel.
(C) Where the ground-fault circuit-interrupter protection required by paragraph (b)(3)(ii)(B) of this section is not
available for receptacles other than
125-volt, single-phase, 15-, 20-, and 30ampere, the employer shall establish
and implement an assured equipment
grounding conductor program covering
cord sets, receptacles that are not a
part of the building or structure, and
equipment connected by cord and plug
§ 1910.304
that are available for use or used by
employees on those receptacles. This
program shall comply with the following requirements:
(1) A written description of the program, including the specific procedures
adopted by the employer, shall be
available at the jobsite for inspection
and copying by the Assistant Secretary
of Labor and any affected employee;
(2) The employer shall designate one
or more competent persons to implement the program;
(3) Each cord set, attachment cap,
plug, and receptacle of cord sets, and
any equipment connected by cord and
plug, except cord sets and receptacles
which are fixed and not exposed to
damage, shall be visually inspected before each day’s use for external defects,
such as deformed or missing pins or insulation damage, and for indications of
possible internal damage. Equipment
found damaged or defective shall not
be used until repaired;
(4) The following tests shall be performed on all cord sets and receptacles
which are not a part of the permanent
wiring of the building or structure, and
cord- and plug-connected equipment required to be grounded:
(i) All equipment grounding conductors shall be tested for continuity and
shall be electrically continuous;
(ii) Each receptacle and attachment
cap or plug shall be tested for correct
attachment of the equipment grounding conductor. The equipment grounding conductor shall be connected to its
proper terminal; and
(iii) All required tests shall be performed before first use; before equipment is returned to service following
any repairs; before equipment is used
after any incident which can be reasonably suspected to have caused damage
(for example, when a cord set is run
over); and at intervals not to exceed 3
months, except that cord sets and receptacles which are fixed and not exposed to damage shall be tested at intervals not exceeding 6 months;
(5) The employer shall not make
available or permit the use by employees of any equipment which has not
met the requirements of paragraph
(b)(3)(ii)(C) of this section; and
(6) Tests performed as required in
paragraph (b)(3)(ii)(C) of this section
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§ 1910.304
29 CFR Ch. XVII (7–1–14 Edition)
shall be recorded. This test record shall
identify each receptacle, cord set, and
cord- and plug-connected equipment
that passed the test and shall indicate
the last date it was tested or the interval for which it was tested. This record
shall be kept by means of logs, color
coding, or other effective means and
shall be maintained until replaced by a
more current record. The record shall
be made available on the jobsite for inspection by the Assistant Secretary
and any affected employee.
(4) Outlet devices. Outlet devices shall
have an ampere rating not less than
the load to be served and shall comply
with the following provisions:
(i) Where connected to a branch circuit having a rating in excess of 20 amperes, lampholders shall be of the
heavy-duty
type.
A
heavy-duty
lampholder shall have a rating of not
less than 660 watts if of the admedium
type and not less than 750 watts if of
any other type; and
(ii) Receptacle outlets shall comply
with the following provisions:
(A) A single receptacle installed on
an individual branch circuit shall have
an ampere rating of not less than that
of the branch circuit;
(B) Where connected to a branch circuit supplying two or more receptacles
or outlets, a receptacle may not supply
a total cord- and plug-connected load
in excess of the maximum specified in
Table S–4; and
(C) Where connected to a branch circuit supplying two or more receptacles
or outlets, receptacle ratings shall conform to the values listed in Table S–5;
or, where larger than 50 amperes, the
receptacle rating may not be less than
the branch-circuit rating. However, receptacles of cord- and plug-connected
arc welders may have ampere ratings
not less than the minimum branch-circuit conductor ampacity.
(5) Cord connections. A receptacle outlet shall be installed wherever flexible
cords with attachment plugs are used.
Where flexible cords are permitted to
be permanently connected, receptacles
may be omitted.
TABLE S–4—MAXIMUM CORD- AND PLUGCONNECTED LOAD TO RECEPTACLE
Receptacle
rating
(amperes)
Circuit rating
(amperes)
15 or 20 .....................................
20 ...............................................
30 ...............................................
15
20
30
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16
24
TABLE S–5—RECEPTACLE RATINGS FOR
VARIOUS SIZE CIRCUITS
Circuit rating
(amperes)
15
20
30
40
50
...........................................
...........................................
...........................................
...........................................
...........................................
Receptacle rating
(amperes)
Not over 15.
15 or 20.
30.
40 or 50.
50.
(c) Outside conductors, 600 volts, nominal, or less. The following requirements
apply to branch-circuit, feeder, and
service conductors rated 600 volts,
nominal, or less and run outdoors as
open conductors.
(1) Conductors on poles. Conductors on
poles shall have a separation of not less
than 305 mm (1.0 ft) where not placed
on racks or brackets. Conductors supported on poles shall provide a horizontal climbing space not less than the
following:
(i) Power conductors below communication conductors—762 mm (30 in.);
(ii) Power conductors alone or above
communication conductors:
(A) 300 volts or less—610 mm (24 in.),
(B) Over 300 volts—762 mm (30 in.);
(iii)
Communication
conductors
below power conductors—same as
power conductors; and
(iv)
Communications
conductors
alone—no requirement.
(2) Clearance from ground. Open conductors, open multiconductor cables,
and service-drop conductors of not over
600 volts, nominal, shall conform to the
minimum clearances specified in Table
S–6.
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Occupational Safety and Health Admin., Labor
§ 1910.304
TABLE S–6—CLEARANCES FROM GROUND
Installations built before August 13, 2007
Distance
Installations built on or after August 13,
2007
Maximum voltage
Conditions
Voltage
to
ground
3.05 m (10.0 ft) ..................................
<600 V ................
<150 V ................
3.66 m (12.0 ft) ..................................
<600 V ................
Above finished grade
or sidewalks, or from
any platform or projection from which
they might be
reached. (If these
areas are accessible
to other than pedestrian traffic, then one
of the other conditions applies).
Over areas, other than
public streets, alleys,
roads, and driveways, subject to vehicular traffic other
than truck traffic.
4.57 m (15.0 ft) ..................................
<600 V ................
Over areas, other than
public streets, alleys,
roads, and driveways, subject to
truck traffic.
301 to 600 V ......
5.49 m (18.0 ft) ..................................
<600 V ................
Over public streets,
alleys, roads, and
driveways.
<600 V ................
(3) Clearance from building openings.
(i) Service conductors installed as open
conductors or multiconductor cable
without an overall outer jacket shall
have a clearance of not less than 914
mm (3.0 ft) from windows that are designed to be opened, doors, porches,
balconies, ladders, stairs, fire escapes,
and similar locations. However, conductors that run above the top level of
a window may be less than 914 mm (3.0
Conditions
<300 V ................
ft) from the window. Vertical clearance
of final spans above, or within 914 mm
(3.0 ft) measured horizontally of, platforms, projections, or surfaces from
which they might be reached shall be
maintained in accordance with paragraph (c)(2) of this section.
(ii) Overhead service conductors may
not be installed beneath openings
through which materials may be
moved, such as openings in farm and
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Above finished grade
or sidewalks, or from
any platform or projection from which
they might be
reached. (If these
areas are accessible
to other than pedestrian traffic, then one
of the other conditions applies.)
Over residential property and driveways.
Over commercial
areas subject to pedestrian traffic or to
vehicular traffic other
than truck traffic.
(This category includes conditions
covered under the
3.05-m (10.0-ft) category where the
voltage exceeds 150
V.)
Over residential property and driveways.
Over commercial
areas subject to pedestrian traffic or to
vehicular traffic other
than truck traffic.
(This category includes conditions
covered under the
3.05-m (10.0-ft) category where the
voltage exceeds 300
V.)
Over public streets,
alleys, roads, and
driveways. Over
commercial areas
subject to truck traffic. Other land traversed by vehicles,
including land used
for cultivating or
grazing and forests
and orchards.
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31
§ 1910.304
29 CFR Ch. XVII (7–1–14 Edition)
commercial buildings, and may not be
installed where they will obstruct entrance to these building openings.
(4) Above roofs. Overhead spans of
open conductors and open multiconductor cables shall have a vertical
clearance of not less than 2.44 m (8.0 ft)
above the roof surface. The vertical
clearance above the roof level shall be
maintained for a distance not less than
914 mm (3.0 ft) in all directions from
the edge of the roof.
(i) The area above a roof surface subject to pedestrian or vehicular traffic
shall have a vertical clearance from
the roof surface in accordance with the
clearance requirements of paragraph
(c)(2) of this section.
(ii) A reduction in clearance to 914
mm (3.0 ft) is permitted where the voltage between conductors does not exceed 300 and the roof has a slope of 102
mm (4 in.) in 305 mm (12 in.) or greater.
(iii) A reduction in clearance above
only the overhanging portion of the
roof to not less than 457 mm (18 in.) is
permitted where the voltage between
conductors does not exceed 300 if:
(A) The conductors do not pass above
the roof overhang for a distance of
more than 1.83 m (6.0 ft), 1.22 m (4.0 ft)
horizontally, and
(B) The conductors are terminated at
a through-the-roof raceway or approved support.
(iv) The requirement for maintaining
a vertical clearance of 914 mm (3.0 ft)
from the edge of the roof does not
apply to the final conductor span,
where the conductors are attached to
the side of a building.
(d) Location of outdoor lamps. Lamps
for outdoor lighting shall be located
below all energized conductors, transformers, or other electric equipment,
unless such equipment is controlled by
a disconnecting means that can be
locked in the open position, or unless
adequate clearances or other safeguards are provided for relamping operations.
(e) Services—(1) Disconnecting means.
(i) Means shall be provided to disconnect all conductors in a building or
other structure from the service-entrance conductors. The service disconnecting means shall plainly indicate whether it is in the open or closed
position and shall be installed at a
readily accessible location nearest the
point of entrance of the service-entrance conductors.
(ii) Each service disconnecting means
shall simultaneously disconnect all
ungrounded conductors.
(iii) Each service disconnecting
means shall be suitable for the prevailing conditions.
(2) Services over 600 volts, nominal. The
following
additional
requirements
apply to services over 600 volts, nominal.
(i) Service-entrance conductors installed as open wires shall be guarded
to make them accessible only to qualified persons.
(ii) Signs warning of high voltage
shall be posted where unqualified employees might come in contact with
live parts.
(f) Overcurrent protection—(1) 600 volts,
nominal, or less. The following requirements apply to overcurrent protection
of circuits rated 600 volts, nominal, or
less.
(i) Conductors and equipment shall
be protected from overcurrent in accordance with their ability to safely
conduct current.
(ii) Except for motor running overload protection, overcurrent devices
may not interrupt the continuity of
the grounded conductor unless all conductors of the circuit are opened simultaneously.
(iii) A disconnecting means shall be
provided on the supply side of all fuses
in circuits over 150 volts to ground and
cartridge fuses in circuits of any voltage where accessible to other than
qualified persons so that each individual circuit containing fuses can be
independently disconnected from the
source of power. However, a currentlimiting
device
without
a
disconnecting means is permitted on the
supply side of the service disconnecting
means. In addition, a single disconnecting means is permitted on the
supply side of more than one set of
fuses as permitted by the exception in
§ 1910.305(j)(4)(vi) for group operation of
motors, and a single disconnecting
means is permitted for fixed electric
space-heating equipment.
(iv) Overcurrent devices shall be
readily accessible to each employee or
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31
Occupational Safety and Health Admin., Labor
authorized building management personnel. These overcurrent devices may
not be located where they will be exposed to physical damage or in the vicinity of easily ignitable material.
(v) Fuses and circuit breakers shall
be so located or shielded that employees will not be burned or otherwise injured by their operation. Handles or levers of circuit breakers, and similar
parts that may move suddenly in such
a way that persons in the vicinity are
likely to be injured by being struck by
them, shall be guarded or isolated.
(vi) Circuit breakers shall clearly indicate whether they are in the open
(off) or closed (on) position.
(vii) Where circuit breaker handles
on switchboards are operated vertically
rather
than
horizontally
or
rotationally, the up position of the
handle shall be the closed (on) position.
(viii) Circuit breakers used as switches in 120-volt and 277-volt, fluorescent
lighting circuits shall be listed and
marked ‘‘SWD.’’
(ix) A circuit breaker with a straight
voltage rating, such as 240 V or 480 V,
may only be installed in a circuit in
which the nominal voltage between
any two conductors does not exceed the
circuit breaker’s voltage rating. A twopole circuit breaker may not be used
for protecting a 3-phase, cornergrounded delta circuit unless the circuit breaker is marked 1F—3F to indicate such suitability. A circuit breaker
with a slash rating, such as 120/240 V or
480Y/277 V, may only be installed in a
circuit where the nominal voltage of
any conductor to ground does not exceed the lower of the two values of the
circuit breaker’s voltage rating and the
nominal voltage between any two conductors does not exceed the higher
value of the circuit breaker’s voltage
rating.
(2) Feeders and branch circuits over 600
volts, nominal. The following requirements apply to feeders and branch circuits energized at more than 600 volts,
nominal:
(i) Feeder and branch-circuit conductors shall have overcurrent protection
in each ungrounded conductor located
at the point where the conductor receives its supply or at a location in the
circuit determined under engineering
supervision;
§ 1910.304
(A) Circuit breakers used for overcurrent protection of three-phase circuits
shall have a minimum of three overcurrent relays operated from three current transformers. On three-phase,
three-wire circuits, an overcurrent
relay in the residual circuit of the current transformers may replace one of
the phase relays. An overcurrent relay,
operated from a current transformer
that links all phases of a three-phase,
three-wire circuit, may replace the residual relay and one other phase-conductor current transformer. Where the
neutral is not grounded on the load
side of the circuit, the current transformer may link all three phase conductors and the grounded circuit conductor (neutral); and
(B) If fuses are used for overcurrent
protection, a fuse shall be connected in
series with each ungrounded conductor;
(ii) Each protective device shall be
capable of detecting and interrupting
all values of current that can occur at
its location in excess of its trip setting
or melting point;
(iii) The operating time of the protective device, the available short-circuit current, and the conductor used
shall be coordinated to prevent damaging or dangerous temperatures in
conductors or conductor insulation
under short-circuit conditions; and
(iv) The following additional requirements apply to feeders only:
(A) The continuous ampere rating of
a fuse may not exceed three times the
ampacity of the conductors. The longtime trip element setting of a breaker
or the minimum trip setting of an electronically actuated fuse may not exceed six times the ampacity of the conductor. For fire pumps, conductors
may be protected for short circuit
only; and
(B) Conductors tapped to a feeder
may be protected by the feeder overcurrent device where that overcurrent
device also protects the tap conductor.
(g) Grounding. Paragraphs (g)(1)
through (g)(9) of this section contain
grounding requirements for systems,
circuits, and equipment.
(1) Systems to be grounded. Systems
that supply premises wiring shall be
grounded as follows:
(i) All 3-wire dc systems shall have
their neutral conductor grounded;
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31
§ 1910.304
29 CFR Ch. XVII (7–1–14 Edition)
(ii) Two-wire dc systems operating at
over 50 volts through 300 volts between
conductors shall be grounded unless:
(A) They supply only industrial
equipment in limited areas and are
equipped with a ground detector;
(B) They are rectifier-derived from
an ac system complying with paragraphs (g)(1)(iii), (g)(1)(iv), and (g)(1)(v)
of this section; or
(C) They are fire-alarm circuits having a maximum current of 0.030 amperes;
(iii) AC circuits of less than 50 volts
shall be grounded if they are installed
as overhead conductors outside of
buildings or if they are supplied by
transformers and the transformer primary supply system is ungrounded or
exceeds 150 volts to ground;
(iv) AC systems of 50 volts to 1000
volts shall be grounded under any of
the following conditions, unless exempted by paragraph (g)(1)(v) of this
section:
(A) If the system can be so grounded
that the maximum voltage to ground
on the ungrounded conductors does not
exceed 150 volts;
(B) If the system is nominally rated
three-phase, four-wire wye connected
in which the neutral is used as a circuit conductor;
(C) If the system is nominally rated
three-phase, four-wire delta connected
in which the midpoint of one phase is
used as a circuit conductor; or
(D) If a service conductor is
uninsulated;
(v) AC systems of 50 volts to 1000
volts are not required to be grounded
under any of the following conditions:
(A) If the system is used exclusively
to supply industrial electric furnaces
for melting, refining, tempering, and
the like;
(B) If the system is separately derived and is used exclusively for rectifiers supplying only adjustable speed
industrial drives;
(C) If the system is separately derived and is supplied by a transformer
that has a primary voltage rating less
than 1000 volts, provided all of the following conditions are met:
(1) The system is used exclusively for
control circuits;
(2) The conditions of maintenance
and supervision ensure that only quali-
fied persons will service the installation;
(3) Continuity of control power is required; and
(4) Ground detectors are installed on
the control system;
(D) If the system is an isolated power
system that supplies circuits in health
care facilities; or
(E) If the system is a high-impedance
grounded neutral system in which a
grounding impedance, usually a resistor, limits the ground-fault current to
a low value for 3-phase ac systems of
480 volts to 1000 volts provided all of
the following conditions are met:
(1) The conditions of maintenance
and supervision ensure that only qualified persons will service the installation;
(2) Continuity of power is required;
(3) Ground detectors are installed on
the system; and
(4) Line-to-neutral loads are not
served.
(2) Conductor to be grounded. The conductor to be grounded for ac premises
wiring systems required to be grounded
by paragraph (g)(1) of this section shall
be as follows:
(i) One conductor of a single-phase,
two-wire system shall be grounded;
(ii) The neutral conductor of a singlephase, three-wire system shall be
grounded;
(iii) The common conductor of a multiphase system having one wire common to all phases shall be grounded;
(iv) One phase conductor of a multiphase system where one phase is
grounded shall be grounded; and
(v) The neutral conductor of a multiphase system in which one phase is
used as a neutral conductor shall be
grounded.
(3) Portable and vehicle-mounted generators. (i) The frame of a portable generator need not be grounded and may
serve as the grounding electrode for a
system supplied by the generator under
the following conditions:
(A) The generator supplies only
equipment mounted on the generator
or cord- and plug-connected equipment
through receptacles mounted on the
generator, or both; and
(B) The noncurrent-carrying metal
parts of equipment and the equipment
grounding conductor terminals of the
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Occupational Safety and Health Admin., Labor
receptacles are bonded to the generator
frame.
(ii) The frame of a vehicle need not
be grounded and may serve as the
grounding electrode for a system supplied by a generator located on the vehicle under the following conditions:
(A) The frame of the generator is
bonded to the vehicle frame;
(B) The generator supplies only
equipment located on the vehicle and
cord- and plug-connected equipment
through receptacles mounted on the
vehicle;
(C) The noncurrent-carrying metal
parts of equipment and the equipment
grounding conductor terminals of the
receptacles are bonded to the generator
frame; and
(D) The system complies with all
other provisions of paragraph (g) of
this section.
(iii) A system conductor that is required to be grounded by the provisions
of paragraph (g)(2) of this section shall
be bonded to the generator frame
where the generator is a component of
a separately derived system.
(4) Grounding connections. (i) For a
grounded system, a grounding electrode conductor shall be used to connect both the equipment grounding
conductor and the grounded circuit
conductor to the grounding electrode.
Both the equipment grounding conductor and the grounding electrode
conductor shall be connected to the
grounded circuit conductor on the supply side of the service disconnecting
means or on the supply side of the system disconnecting means or overcurrent devices if the system is separately
derived.
(ii) For an ungrounded service-supplied system, the equipment grounding
conductor shall be connected to the
grounding electrode conductor at the
service equipment. For an ungrounded
separately derived system, the equipment grounding conductor shall be
connected to the grounding electrode
conductor at, or ahead of, the system
disconnecting means or overcurrent devices.
(iii) On extensions of existing branch
circuits that do not have an equipment
grounding conductor, grounding-type
receptacles may be grounded to a
grounded cold water pipe near the
§ 1910.304
equipment if the extension was installed before August 13, 2007. When
any element of this branch circuit is
replaced, the entire branch circuit
shall use an equipment grounding conductor that complies with all other
provisions of paragraph (g) of this section.
(5) Grounding path. The path to
ground from circuits, equipment, and
enclosures shall be permanent, continuous, and effective.
(6) Supports, enclosures, and equipment
to be grounded. (i) Metal cable trays,
metal raceways, and metal enclosures
for conductors shall be grounded, except that:
(A) Metal enclosures such as sleeves
that are used to protect cable assemblies from physical damage need not be
grounded; and
(B) Metal enclosures for conductors
added to existing installations of open
wire, knob-and-tube wiring, and nonmetallic-sheathed cable need not be
grounded if all of the following conditions are met:
(1) Runs are less than 7.62 meters
(25.0 ft);
(2) Enclosures are free from probable
contact with ground, grounded metal,
metal laths, or other conductive materials; and
(3) Enclosures are guarded against
employee contact.
(ii) Metal enclosures for service
equipment shall be grounded.
(iii) Frames of electric ranges, wallmounted ovens, counter-mounted cooking units, clothes dryers, and metal
outlet or junction boxes that are part
of the circuit for these appliances shall
be grounded.
(iv)
Exposed
noncurrent-carrying
metal parts of fixed equipment that
may become energized shall be grounded under any of the following conditions:
(A) If within 2.44 m (8 ft) vertically or
1.52 m (5 ft) horizontally of ground or
grounded metal objects and subject to
employee contact;
(B) If located in a wet or damp location and not isolated;
(C) If in electrical contact with
metal;
(D) If in a hazardous (classified) location;
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31
§ 1910.304
29 CFR Ch. XVII (7–1–14 Edition)
(E) If supplied by a metal-clad,
metal-sheathed, or grounded metal
raceway wiring method; or
(F) If equipment operates with any
terminal at over 150 volts to ground.
(v) Notwithstanding the provisions of
paragraph (g)(6)(iv) of this section, exposed noncurrent-carrying metal parts
of the following types of fixed equipment need not be grounded:
(A) Enclosures for switches or circuit
breakers used for other than service
equipment and accessible to qualified
persons only;
(B) Electrically heated appliances
that are permanently and effectively
insulated from ground;
(C) Distribution apparatus, such as
transformer
and
capacitor
cases,
mounted on wooden poles, at a height
exceeding 2.44 m (8.0 ft) above ground
or grade level; and
(D) Listed equipment protected by a
system of double insulation, or its
equivalent, and distinctively marked
as such.
(vi)
Exposed
noncurrent-carrying
metal parts of cord- and plug-connected equipment that may become energized shall be grounded under any of
the following conditions:
(A) If in hazardous (classified) locations (see § 1910.307);
(B) If operated at over 150 volts to
ground, except for guarded motors and
metal frames of electrically heated appliances if the appliance frames are
permanently and effectively insulated
from ground;
(C) If the equipment is of the following types:
(1) Refrigerators, freezers, and air
conditioners;
(2) Clothes-washing, clothes-drying,
and
dishwashing
machines,
sump
pumps, and electric aquarium equipment;
(3) Hand-held motor-operated tools,
stationary and fixed motor-operated
tools, and light industrial motor-operated tools;
(4) Motor-operated appliances of the
following types: hedge clippers, lawn
mowers, snow blowers, and wet scrubbers;
(5) Cord- and plug-connected appliances used in damp or wet locations, or
by employees standing on the ground
or on metal floors or working inside of
metal tanks or boilers;
(6) Portable and mobile X-ray and associated equipment;
(7) Tools likely to be used in wet and
conductive locations; and
(8 Portable hand lamps.
(vii) Notwithstanding the provisions
of paragraph (g)(6)(vi) of this section,
the following equipment need not be
grounded:
(A) Tools likely to be used in wet and
conductive
locations
if
supplied
through an isolating transformer with
an ungrounded secondary of not over 50
volts; and
(B) Listed or labeled portable tools
and appliances if protected by an approved system of double insulation, or
its
equivalent,
and
distinctively
marked.
(7) Nonelectrical equipment. The metal
parts of the following nonelectrical
equipment shall be grounded: frames
and tracks of electrically operated
cranes and hoists; frames of nonelectrically driven elevator cars to which
electric conductors are attached; handoperated metal shifting ropes or cables
of electric elevators; and metal partitions, grill work, and similar metal enclosures around equipment of over 750
volts between conductors.
(8) Methods of grounding fixed equipment. (i) Noncurrent-carrying metal
parts of fixed equipment, if required to
be grounded by this subpart, shall be
grounded by an equipment grounding
conductor that is contained within the
same raceway, cable, or cord, or runs
with or encloses the circuit conductors.
For dc circuits only, the equipment
grounding conductor may be run separately from the circuit conductors.
(ii) Electric equipment is considered
to be effectively grounded if it is secured to, and in electrical contact
with, a metal rack or structure that is
provided for its support and the metal
rack or structure is grounded by the
method specified for the noncurrentcarrying metal parts of fixed equipment in paragraph (g)(8)(i) of this section. Metal car frames supported by
metal hoisting cables attached to or
running over metal sheaves or drums of
grounded elevator machines are also
considered to be effectively grounded.
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Occupational Safety and Health Admin., Labor
(iii) For installations made before
April 16, 1981, electric equipment is
also considered to be effectively
grounded if it is secured to, and in metallic contact with, the grounded structural metal frame of a building. When
any element of this branch circuit is
replaced, the entire branch circuit
shall use an equipment grounding conductor that complies with all other
provisions of paragraph (g) of this section.
(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
delta-connected 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
§ 1910.305
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, polemounted distribution apparatus at a
height exceeding 2.44 m (8.0 ft) above
ground or grade level need not be
grounded.
[46 FR 4056, Jan. 16, 1981, as amended at 73
FR 64205, Oct. 29, 2008]
§ 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,
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31
§ 1910.305
29 CFR Ch. XVII (7–1–14 Edition)
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.
(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; mineral-insulated, metal-sheathed cable; multiconductor service-entrance cable; multiconductor underground feeder and
branch-circuit cable; multipurpose and
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31
Occupational Safety and Health Admin., Labor
communications cables; nonmetallicsheathed 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, ventilatedtrough, 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.)
(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.
§ 1910.305
(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 deadend 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
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§ 1910.305
29 CFR Ch. XVII (7–1–14 Edition)
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:
(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, well-rounded 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
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. 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.
(3) Connection of switches. (i) Singlethrow 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,
molded-case 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
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Occupational Safety and Health Admin., Labor
means to ground metal faceplates,
whether or not a metal faceplate is installed. However, if no grounding
means exists within the snap-switch
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, 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.
§ 1910.305
(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;
(E) Where concealed behind building
walls, ceilings, or floors; or
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§ 1910.305
29 CFR Ch. XVII (7–1–14 Edition)
(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. Hard-service cord and junior hardservice 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.
(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
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Occupational Safety and Health Admin., Labor
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 20ampere 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
grounding-type 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
§ 1910.305
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.
(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.
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§ 1910.305
29 CFR Ch. XVII (7–1–14 Edition)
(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 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
electrostatic-coating 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 liquidinsulated, 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 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
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Occupational Safety and Health Admin., Labor
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
TION. Piping or other
(j)(5)(vii) OF THIS SECfacilities 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:
(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;
§ 1910.306
(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. (i) Each sign
and outline lighting system, or feeder
circuit or branch circuit supplying a
sign or outline lighting system, shall
be controlled by an externally operable
switch or circuit breaker that will open
all ungrounded conductors. However, a
disconnecting means is not required for
an exit directional sign located within
a building or for cord-connected signs
with an attachment plug.
(ii) Signs and outline lighting systems located within fountains shall
have the disconnect located at least
1.52 m (5.0 ft) from the inside walls of
the fountain.
(2) Location. (i) The disconnecting
means shall be within sight of the sign
or outline lighting system that it controls. Where the disconnecting means
is out of the line of sight from any section that may be energized, the disconnecting means shall be capable of
being locked in the open position.
(ii) Signs or outline lighting systems
operated
by
electronic
or
electromechanical controllers located
external to the sign or outline lighting
system may have a disconnecting
means located within sight of the controller or in the same enclosure with
the controller. The disconnecting
means shall disconnect the sign or outline lighting system and the controller
from all ungrounded supply conductors. It shall be designed so no pole can
be operated independently and shall be
capable of being locked in the open position.
(iii) 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
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§ 1910.306
29 CFR Ch. XVII (7–1–14 Edition)
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 for runway
conductors. A disconnecting means
shall be provided between the runway
contact conductors and the power supply. Such disconnecting means shall
consist of a motor-circuit switch, circuit breaker, or molded case switch.
The disconnecting means shall open all
ungrounded conductors simultaneously
and shall be:
(i) Readily accessible and operable
from the ground or floor level;
(ii) Arranged to be locked in the open
position; and
(iii) Placed within view of the runway contact conductors.
(2) Disconnecting means for cranes and
monorail hoists. (i) Except as provided
in paragraph (b)(2)(iv) of this section, a
motor-circuit switch, molded case
switch, or circuit breaker shall be provided in the leads from the runway
contact conductors or other power supply on all cranes and monorail hoists.
(ii) The disconnecting means shall be
capable of being locked in the open position.
(iii) Means shall be provided at the
operating station to open the power
circuit to all motors of the crane or
monorail hoist where the disconnecting
means is not readily accessible from
the crane or monorail hoist operating
station.
(iv) The disconnecting means may be
omitted where a monorail hoist or
hand-propelled crane bridge installation meets all of the following conditions:
(A) The unit is controlled from the
ground or floor level;
(B) The unit is within view of the
power supply disconnecting means; and
(C) No fixed work platform has been
provided for servicing the unit.
(3) Limit switch. 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.
(4) Clearance. The dimension of the
working space in the direction of ac-
cess to live parts that may require examination, adjustment, servicing, or
maintenance while alive shall be a
minimum of 762 mm (2.5 ft). Where controls are enclosed in cabinets, the
doors shall either open at least 90 degrees or be removable.
(c) Elevators, dumbwaiters, escalators,
moving walks, wheelchair lifts, and stairway chair lifts. The following requirements apply to elevators, dumbwaiters,
escalators, moving walks, wheelchair
lifts, and stairway chair lifts.
(1) Disconnecting means. Elevators,
dumbwaiters,
escalators,
moving
walks, wheelchair lifts, and stairway
chair lifts shall have a single means for
disconnecting all ungrounded main
power supply conductors for each unit.
(2) Control panels. Control panels not
located in the same space as the drive
machine shall be located in cabinets
with doors or panels capable of being
locked closed.
(3) Type. The disconnecting means
shall be an enclosed externally operable fused motor circuit switch or circuit breaker capable of being locked in
the open position. The disconnecting
means shall be a listed device.
(4) Operation. No provision may be
made to open or close this disconnecting means from any other part
of the premises. If sprinklers are installed in hoistways, machine rooms,
or machinery spaces, the disconnecting
means may automatically open the
power supply to the affected elevators
prior to the application of water. No
provision may be made to close this
disconnecting means automatically
(that is, power may only be restored by
manual means).
(5) Location. The disconnecting means
shall be located where it is readily accessible to qualified persons.
(i) On elevators without generator
field control, the disconnecting means
shall be located within sight of the
motor controller. Driving machines or
motion and operation controllers not
within sight of the disconnecting
means shall be provided with a manually operated switch installed in the
control circuit adjacent to the equipment in order to prevent starting.
Where the driving machine is located
in a remote machinery space, a single
disconnecting means for disconnecting
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Occupational Safety and Health Admin., Labor
all ungrounded main power supply conductors shall be provided and be capable of being locked in the open position.
(ii) On elevators with generator field
control, the disconnecting means shall
be located within sight of the motor
controller for the driving motor of the
motor-generator set. Driving machines,
motor-generator sets, or motion and
operation controllers not within sight
of the disconnecting means shall be
provided with a manually operated
switch installed in the control circuit
to prevent starting. The manually operated switch shall be installed adjacent to this equipment. Where the driving machine or the motor-generator set
is located in a remote machinery
space, a single means for disconnecting
all ungrounded main power supply conductors shall be provided and be capable of being locked in the open position.
(iii) On escalators and moving walks,
the disconnecting means shall be installed in the space where the controller is located.
(iv) On wheelchair lifts and stairway
chair lifts, the disconnecting means
shall be located within sight of the
motor controller.
(6) Identification and signs. (i) Where
there is more than one driving machine
in a machine room, the disconnecting
means shall be numbered to correspond
to the identifying number of the driving machine that they control.
(ii) The disconnecting means shall be
provided with a sign to identify the location of the supply-side overcurrent
protective device.
(7) Single-car and multicar installations. On single-car and multicar installations, equipment receiving electrical power from more than one source
shall be provided with a disconnecting
means for each source of electrical
power. The disconnecting means shall
be within sight of the equipment
served.
(8) Warning sign for multiple disconnecting means. A warning sign shall
be mounted on or next to the disconnecting means where multiple disconnecting means are used and parts of
the controllers remain energized from
a source other than the one disconnected. The sign shall be clearly legible
§ 1910.306
and shall read ‘‘WARNING—PARTS OF
THE CONTROLLER ARE NOT DEENERGIZED BY THIS SWITCH.’’
(9) Interconnection between multicar
controllers. A warning sign worded as
required in paragraph (c)(8) of this section shall be mounted on or next to the
disconnecting means where interconnections between controllers are
necessary for the operation of the system on multicar installations that remain energized from a source other
than the one disconnected.
(10) Motor controllers. Motor controllers may be located outside the spaces
otherwise required by paragraph (c) of
this section, provided they are in enclosures with doors or removable panels capable of being locked closed and
the disconnecting means is located adjacent to or is an integral part of the
motor controller. Motor controller enclosures for escalators or moving walks
may be located in the balustrade on
the side located away from the moving
steps or moving treadway. If the disconnecting means is an integral part of
the motor controller, it shall be operable without opening the enclosure.
(d)
Electric
welders—disconnecting
means—(1) Arc welders. A disconnecting
means shall be provided in the supply
circuit for each arc welder that is not
equipped with a disconnect mounted as
an integral part of the welder. The disconnecting means shall be a switch or
circuit breaker, and its rating may not
be less than that necessary to accommodate overcurrent protection.
(2) Resistance welders. A switch or circuit breaker shall be provided by which
each resistance welder and its control
equipment can be disconnected from
the supply circuit. The ampere rating
of this disconnecting means may not be
less
than
the
supply
conductor
ampacity. The supply circuit switch
may be used as the welder disconnecting means where the circuit
supplies only one welder.
(e) Information technology equipment—
(1) Disconnecting means. A means shall
be provided to disconnect power to all
electronic equipment in an information
technology equipment room. There
shall also be a similar means to disconnect the power to all dedicated
heating, ventilating, and air-conditioning (HVAC) systems serving the
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§ 1910.306
29 CFR Ch. XVII (7–1–14 Edition)
room and to cause all required fire/
smoke dampers to close.
(2) Grouping. The control for these
disconnecting means shall be grouped
and identified and shall be readily accessible at the principal exit doors. A
single means to control both the electronic equipment and HVAC system is
permitted.
(3) Exception. Integrated electrical
systems covered by § 1910.308(g) need
not have the disconnecting means required by paragraph (e)(1) of this section.
(f) X-Ray equipment. This paragraph
applies to X-ray equipment.
(1) Disconnecting means. (i) A disconnecting means shall be provided in
the supply circuit. The disconnecting
means shall be operable from a location readily accessible from the X-ray
control. For equipment connected to a
120-volt branch circuit of 30 amperes or
less, a grounding-type attachment plug
cap and receptacle of proper rating
may serve as a disconnecting means.
(ii) If more than one piece of equipment is operated from the same highvoltage circuit, each piece or each
group of equipment as a unit shall be
provided with a high-voltage switch or
equivalent disconnecting means. The
disconnecting means shall be constructed, enclosed, or located so as to
avoid contact by employees with its
live parts.
(2) Control. The following requirements apply to industrial and commercial laboratory equipment.
(i) Radiographic and fluoroscopictype equipment shall be effectively enclosed or shall have interlocks that deenergize the equipment automatically
to prevent ready access to live currentcarrying parts.
(ii) Diffraction- and irradiation-type
equipment shall have a pilot light,
readable meter deflection, or equivalent means to indicate when the equipment is energized, unless the equipment or installation is effectively enclosed or is provided with interlocks to
prevent access to live current-carrying
parts during operation.
(g) Induction and dielectric heating
equipment. This paragraph applies to
induction and dielectric heating equipment and accessories for industrial and
scientific applications, but not for
medical or dental applications or for
appliances.
(1) Guarding and grounding. (i) The
converting apparatus (including the dc
line) and high-frequency electric circuits (excluding the output circuits
and remote-control circuits) shall be
completely contained within enclosures of noncombustible material.
(ii) All panel controls shall be of
dead-front construction.
(iii) Doors or detachable panels shall
be employed for internal access. Where
doors are used giving access to voltages
from 500 to 1000 volts ac or dc, either
door locks shall be provided or interlocks shall be installed. Where doors
are used giving access to voltages of
over 1000 volts ac or dc, either mechanical lockouts with a disconnecting
means to prevent access until circuit
parts within the cubicle are deenergized, or both door interlocking and
mechanical door locks, shall be provided. Detachable panels not normally
used for access to such parts shall be
fastened in a manner that will make
them difficult to remove (for example,
by requiring the use of tools).
(iv) Warning labels or signs that read
‘‘DANGER—HIGH
VOLTAGE—KEEP
OUT’’ shall be attached to the equipment and shall be plainly visible where
persons might contact energized parts
when doors are opened or closed or
when panels are removed from compartments containing over 250 volts ac
or dc.
(v) Induction and dielectric heating
equipment shall be protected as follows:
(A) Protective cages or adequate
shielding shall be used to guard work
applicators other than induction heating coils.
(B) Induction heating coils shall be
protected by insulation or refractory
materials or both.
(C) Interlock switches shall be used
on all hinged access doors, sliding panels, or other such means of access to
the applicator, unless the applicator is
an induction heating coil at dc ground
potential or operating at less than 150
volts ac.
(D) Interlock switches shall be connected in such a manner as to remove
all power from the applicator when any
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Occupational Safety and Health Admin., Labor
one of the access doors or panels is
open.
(vi)
A
readily
accessible
disconnecting means shall be provided by
which each heating equipment can be
isolated from its supply circuit. The
ampere rating of this disconnecting
means may not be less than the nameplate current rating of the equipment.
The
supply
circuit
disconnecting
means is permitted as a heating equipment disconnecting means where the
circuit supplies only one piece of equipment.
(2) Remote control. (i) If remote controls are used for applying power, a selector switch shall be provided and
interlocked to provide power from only
one control point at a time.
(ii) Switches operated by foot pressure shall be provided with a shield
over the contact button to avoid accidental closing of the switch.
(h) Electrolytic cells. This paragraph
applies to the installation of the electrical components and accessory equipment of electrolytic cells, electrolytic
cell lines, and process power supply for
the production of aluminum, cadmium,
chlorine, copper, fluorine, hydrogen
peroxide, magnesium, sodium, sodium
chlorate, and zinc. Cells used as a
source of electric energy and for electroplating processes and cells used for
production of hydrogen are not covered
by this paragraph.
(1) Application. Installations covered
by paragraph (h) of this section shall
comply with all applicable provisions
of this subpart, except as follows:
(i) Overcurrent protection of electrolytic cell dc process power circuits
need not comply with the requirements
of § 1910.304(f);
(ii) Equipment located or used within
the cell line working zone or associated
with the cell line dc power circuits
need not comply with the provisions of
§ 1910.304(g); and
(iii) Electrolytic cells, cell line conductors, cell line attachments, and the
wiring of auxiliary equipment and devices within the cell line working zone
need not comply with the provisions of
§ 1910.303 or § 1910.304(b) and (c).
(2) Disconnecting means. If more than
one dc cell line process power supply
serves the same cell line, a disconnecting means shall be provided on
§ 1910.306
the cell line circuit side of each power
supply to disconnect it from the cell
line circuit. Removable links or removable conductors may be used as the disconnecting means.
(3) Portable electric equipment. (i) The
frames and enclosures of portable electric equipment used within the cell
line working zone may not be grounded, unless the cell line circuit voltage
does not exceed 200 volts DC or the
frames are guarded.
(ii) Ungrounded portable electric
equipment
shall
be
distinctively
marked and shall employ plugs and receptacles of a configuration that prevents connection of this equipment to
grounding receptacles and that prevents
inadvertent
interchange
of
ungrounded and grounded portable
electric equipment.
(4) Power supply circuits and receptacles for portable electric equipment. (i)
Circuits
supplying
power
to
ungrounded receptacles for hand-held,
cord- and plug-connected equipment
shall meet the following requirements:
(A) The circuits shall be electrically
isolated from any distribution system
supplying areas other than the cell line
working zone and shall be ungrounded;
(B) The circuits shall be supplied
through isolating transformers with
primaries operating at not more than
600 volts between conductors and protected with proper overcurrent protection;
(C) The secondary voltage of the isolating transformers may not exceed 300
volts between conductors; and
(D) All circuits supplied from the
secondaries shall be ungrounded and
shall have an approved overcurrent device of proper rating in each conductor.
(ii) Receptacles and their mating
plugs for ungrounded equipment may
not have provision for a grounding conductor and shall be of a configuration
that prevents their use for equipment
required to be grounded.
(iii) Receptacles on circuits supplied
by an isolating transformer with an
ungrounded secondary:
(A) Shall have a distinctive configuration;
(B) Shall be distinctively marked;
and
(C) May not be used in any other location in the facility.
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§ 1910.306
29 CFR Ch. XVII (7–1–14 Edition)
(5) Fixed and portable electric equipment. (i) The following need not be
grounded:
(A) AC systems supplying fixed and
portable electric equipment within the
cell line working zone; and
(B) Exposed conductive surfaces, such
as electric equipment housings, cabinets, boxes, motors, raceways and the
like that are within the cell line working zone.
(ii) Auxiliary electric equipment,
such as motors, transducers, sensors,
control devices, and alarms, mounted
on an electrolytic cell or other energized surface shall be connected to the
premises wiring systems by any of the
following means:
(A) Multiconductor hard usage or
extra hard usage flexible cord;
(B) Wire or cable in suitable nonmetallic raceways or cable trays; or
(C) Wire or cable in suitable metal
raceways or metal cable trays installed
with insulating breaks such that they
will not cause a potentially hazardous
electrical condition.
(iii) Fixed electric equipment may be
bonded to the energized conductive surfaces of the cell line, its attachments,
or auxiliaries. If fixed electric equipment is mounted on an energized conductive surface, it shall be bonded to
that surface.
(6) Auxiliary nonelectrical connections.
Auxiliary nonelectrical connections
such as air hoses, water hoses, and the
like, to an electrolytic cell, its attachments, or auxiliary equipment may not
have continuous conductive reinforcing
wire, armor, braids, or the like. Hoses
shall be of a nonconductive material.
(7) Cranes and hoists. (i) The conductive surfaces of cranes and hoists that
enter the cell line working zone need
not be grounded. The portion of an
overhead crane or hoist that contacts
an energized electrolytic cell or energized attachments shall be insulated
from ground.
(ii) Remote crane or hoist controls
that may introduce hazardous electrical conditions into the cell line
working zone shall employ one or more
of the following systems:
(A) Isolated and ungrounded control
circuit;
(B) Nonconductive rope operator;
(C) Pendant pushbutton with nonconductive supporting means and with
nonconductive surfaces or ungrounded
exposed conductive surfaces; or
(D) Radio.
(i) Electrically driven or controlled irrigation machines—(1) Lightning protection. If an irrigation machine has a stationary point, a grounding electrode
system shall be connected to the machine at the stationary point for lightning protection.
(2) Disconnecting means. (i) The main
disconnecting means for a center pivot
irrigation machine shall be located at
the point of connection of electrical
power to the machine or shall be visible and not more than 15.2 m (50 ft)
from the machine.
(ii) The disconnecting means shall be
readily accessible and capable of being
locked in the open position.
(iii) A disconnecting means shall be
provided for each motor and controller.
(j) Swimming pools, fountains, and
similar installations. This paragraph applies to electric wiring for and equipment in or adjacent to all swimming,
wading, therapeutic, and decorative
pools and fountains; hydro-massage
bathtubs, whether permanently installed or storable; and metallic auxiliary equipment, such as pumps, filters,
and similar equipment. Therapeutic
pools in health care facilities are exempt from these provisions.
(1) Receptacles. (i) A single receptacle
of the locking and grounding type that
provides power for a permanently installed swimming pool recirculating
pump motor may be located not less
than 1.52 m (5 ft) from the inside walls
of a pool. All other receptacles on the
property shall be located at least 3.05
m (10 ft) from the inside walls of a pool.
(ii) Receptacles that are located
within 4.57 m (15 ft), or 6.08 m (20 ft) if
the installation was built after August
13, 2007, of the inside walls of the pool
shall be protected by ground-fault circuit interrupters.
(iii) Where a pool is installed permanently at a dwelling unit, at least one
125-volt, 15- or 20-ampere receptacle on
a general-purpose branch circuit shall
be located a minimum of 3.05 m (10 ft)
and not more than 6.08 m (20 ft) from
the inside wall of the pool. This receptacle shall be located not more than
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Occupational Safety and Health Admin., Labor
1.98 m (6.5 ft) above the floor, platform,
or grade level serving the pool.
NOTE TO PARAGRAPH (j)(1) OF THIS SECTION:
In determining these dimensions, the distance to be measured is the shortest path the
supply cord of an appliance connected to the
receptacle would follow without piercing a
floor, wall, or ceiling of a building or other
effective permanent barrier.
(2) Lighting fixtures, lighting outlets,
and ceiling suspended (paddle) fans. (i)
In outdoor pool areas, lighting fixtures,
lighting outlets, and ceiling-suspended
(paddle) fans may not be installed over
the pool or over the area extending 1.52
m (5 ft) horizontally from the inside
walls of a pool unless no part of the
lighting fixture of a ceiling-suspended
(paddle) fan is less than 3.66 m (12 ft)
above the maximum water level. However, a lighting fixture or lighting outlet that was installed before April 16,
1981, may be located less than 1.52 m (5
ft) measured horizontally from the inside walls of a pool if it is at least 1.52
m (5 ft) above the surface of the maximum water level and is rigidly attached to the existing structure. It
shall also be protected by a groundfault circuit interrupter installed in
the branch circuit supplying the fixture.
(ii) Lighting fixtures and lighting
outlets installed in the area extending
between 1.52 m (5 ft) and 3.05 m (10 ft)
horizontally from the inside walls of a
pool shall be protected by a groundfault circuit interrupter unless installed 1.52 m (5 ft) above the maximum
water level and rigidly attached to the
structure adjacent to or enclosing the
pool.
(3) Cord- and plug-connected equipment. Flexible cords used with the following equipment may not exceed 0.9 m
(3 ft) in length and shall have a copper
equipment grounding conductor with a
grounding-type attachment plug:
(i) Cord- and plug-connected lighting
fixtures installed within 4.88 m (16 ft)
of the water surface of permanently installed pools; and
(ii) Other cord- and plug-connected,
fixed or stationary equipment used
with permanently installed pools.
(4) Underwater equipment. (i) A
ground-fault circuit interrupter shall
be installed in the branch circuit supplying underwater fixtures operating
§ 1910.306
at more than 15 volts. Equipment installed underwater shall be identified
for the purpose.
(ii) No underwater lighting fixtures
may be installed for operation at over
150 volts between conductors.
(iii) A lighting fixture facing upward
shall have the lens adequately guarded
to prevent contact by any person.
(5) Fountains. All electric equipment,
including power supply cords, operating at more than 15 volts and used
with fountains shall be protected by
ground-fault circuit interrupters.
(k) Carnivals, circuses, fairs, and similar events. This paragraph covers the
installation of portable wiring and
equipment, including wiring in or on
all structures, for carnivals, circuses,
exhibitions, fairs, traveling attractions, and similar events.
(1) Protection of electric equipment.
Electric equipment and wiring methods
in or on rides, concessions, or other
units shall be provided with mechanical protection where such equipment
or wiring methods are subject to physical damage.
(2) Installation. (i) Services shall be
installed in accordance with applicable
requirements of this subpart, and, in
addition, shall comply with the following:
(A) Service equipment may not be installed in a location that is accessible
to unqualified persons, unless the
equipment is lockable; and
(B) Service equipment shall be
mounted on solid backing and installed
so as to be protected from the weather,
unless the equipment is of weatherproof construction.
(ii) Amusement rides and amusement
attractions shall be maintained not
less than 4.57 m (15 ft) in any direction
from overhead conductors operating at
600 volts or less, except for the conductors supplying the amusement ride or
attraction. Amusement rides or attractions may not be located under or
within 4.57 m (15 ft) horizontally of
conductors operating in excess of 600
volts.
(iii) Flexible cords and cables shall be
listed for extra-hard usage. When used
outdoors, flexible cords and cables
shall also be listed for wet locations
and shall be sunlight resistant.
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§ 1910.306
29 CFR Ch. XVII (7–1–14 Edition)
(iv) Single conductor cable shall be
size No. 2 or larger.
(v) Open conductors are prohibited
except as part of a listed assembly or
festoon lighting installed in accordance with § 1910.304(c).
(vi) Flexible cords and cables shall be
continuous without splice or tap between boxes or fittings. Cord connectors may not be laid on the ground unless listed for wet locations. Connectors and cable connections may not be
placed in audience traffic paths or
within areas accessible to the public
unless guarded.
(vii) Wiring for an amusement ride,
attraction, tent, or similar structure
may not be supported by another ride
or structure unless specifically identified for the purpose.
(viii) Flexible cords and cables run on
the ground, where accessible to the
public, shall be covered with approved
nonconductive mats. Cables and mats
shall be arranged so as not to present a
tripping hazard.
(ix) A box or fitting shall be installed
at each connection point, outlet,
switch point, or junction point.
(3) Inside tents and concessions. Electrical wiring for temporary lighting,
where installed inside of tents and concessions, shall be securely installed,
and, where subject to physical damage,
shall be provided with mechanical protection. All temporary lamps for general illumination shall be protected
from accidental breakage by a suitable
fixture or lampholder with a guard.
(4) Portable distribution and termination boxes. Employers may only use
portable distribution and termination
boxes that meet the following requirements:
(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 singlepole 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
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Occupational Safety and Health Admin., Labor
(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 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
§ 1910.307
(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,
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§ 1910.307
29 CFR Ch. XVII (7–1–14 Edition)
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 sys-
tems 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.
(d) 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.
(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. General-purpose equipment or equipment in general-purpose
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
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Occupational Safety and Health Admin., Labor
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 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
§ 1910.307
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.
(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.
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§ 1910.307
29 CFR Ch. XVII (7–1–14 Edition)
(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 location 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
SECTION: An example
(g)(5)(ii)(B) OF THIS
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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Occupational Safety and Health Admin., Labor
§ 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 braid-covered 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.
§ 1910.308
Stress reduction means shall be provided at all terminations of factory-applied 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 fire-resistant 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. 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
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ER14FE07.000
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§ 1910.308
29 CFR Ch. XVII (7–1–14 Edition)
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 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.
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Occupational Safety and Health Admin., Labor
(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.
(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
§ 1910.308
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.
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§ 1910.308
29 CFR Ch. XVII (7–1–14 Edition)
(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 nonpowerlimited 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 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
aerial-drop 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 inspan, 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
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Occupational Safety and Health Admin., Labor
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.
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 photo-
§ 1910.331
voltaic 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 currentcarrying 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.
§§ 1910.309–1910.330
[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
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§ 1910.331
29 CFR Ch. XVII (7–1–14 Edition)
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.
(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]
EFFECTIVE DATE NOTE: At 79 FR 20692, Apr.
11, 2014, § 1910.331 was amended in paragraph
(c)(1) by revising the headings to Notes 1 and
2 and revising Note 3, effective July 10, 2014.
For the convenience of the user, the revised
text is set forth as follows:
§ 1910.331
Scope.
*
*
*
*
(c) * * *
(1) * * *
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*
Occupational Safety and Health Admin., Labor
NOTE 1 TO PARAGRAPH (C)(1): * * *
NOTE 2 TO PARAGRAPH (C)(1): * * *
NOTE 3 TO PARAGRAPH (C)(1): 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 (see the definition of ‘‘line-clearance tree trimming’’ in
§ 1910.269(x)).
(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.
*
*
§ 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.
§ 1910.333
(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.
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 degree 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
Blue collar supervisors. 1
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
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§ 1910.333
29 CFR Ch. XVII (7–1–14 Edition)
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.
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.
(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 deen-
ergized 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.
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Occupational Safety and Health Admin., Labor
(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
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.
§ 1910.333
(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
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.
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§ 1910.333
29 CFR Ch. XVII (7–1–14 Edition)
(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
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.
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:
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Occupational Safety and Health Admin., Labor
(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
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
§ 1910.333
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 conductors 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
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§ 1910.334
29 CFR Ch. XVII (7–1–14 Edition)
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
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.
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Occupational Safety and Health Admin., Labor
(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.
(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.
§ 1910.335
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.
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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.
NOTE: Personal protective equipment requirements are contained in subpart I of this
part.
(ii) Protective equipment shall be
maintained in a safe, reliable condition
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.
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§§ 1910.336–1910.360
29 CFR Ch. XVII (7–1–14 Edition)
(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
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]
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:
(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
(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.’’)
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Occupational Safety and Health Admin., Labor
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
§ 1910.399
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
cell-servicing equipment.
Center pivot irrigation machine. A
multi-motored irrigation machine that
revolves around a central pivot and
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§ 1910.399
29 CFR Ch. XVII (7–1–14 Edition)
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
(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
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
(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.
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Occupational Safety and Health Admin., Labor
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.
(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.
§ 1910.399
(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 positive-pressure 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 operating 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.
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§ 1910.399
29 CFR Ch. XVII (7–1–14 Edition)
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,
SION 2:’’ This classification includes
DIVIlocations 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 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.
NOTE TO THE DEFINITION OF ‘‘CLASS
VISION 1:’’ Such locations usually
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.
(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.
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Occupational Safety and Health Admin., Labor
(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 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.
§ 1910.399
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.
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.
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§ 1910.399
29 CFR Ch. XVII (7–1–14 Edition)
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,
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.’’
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Occupational Safety and Health Admin., Labor
Induction heating. The heating of a
nominally conductive material due to
its own I 2R 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.
§ 1910.399
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.
(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 vehiclewashing 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
metal-sheathed, 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
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§ 1910.399
29 CFR Ch. XVII (7–1–14 Edition)
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.
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 cir-
cuits 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 watt-hour 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
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31
Occupational Safety and Health Admin., Labor
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.
§ 1910.399
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 flameretardant, moisture resistant covering;
and
(2) Type USE. Type USE, identified
for underground use, having a moisture-resistant covering, but not required to have a flame-retardant 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
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§ 1910.399
29 CFR Ch. XVII (7–1–14 Edition)
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.
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,
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
root-mean-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
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Occupational Safety and Health Admin., Labor
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.
[72 FR 7215, Feb. 14, 2007]
EFFECTIVE DATE NOTE: At 79 FR 20692, Apr.
11, 2014, § 1910.399 was amended by removing
the definition of ‘‘line-clearance tree trimming’’, effective July 10, 2014.
APPENDIX A TO SUBPART S OF PART
1910— 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.
Pt. 1910, Subpt. S, App. A
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
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.
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§ 1910.401
29 CFR Ch. XVII (7–1–14 Edition)
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.
[72 FR 7221, Feb., 14, 2007]
Subpart T—Commercial Diving
Operations
AUTHORITY: 29 U.S.C. 653, 655, 657; 40 U.S.C.
333; 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), 6–96 (62 FR 111), 3–2000 (65 FR
50017), 5–2002 (67 FR 65008), 5–2007 (72 FR
31160), or 4–2010 (75 FR 55355) as applicable,
and 29 CFR 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:
(i) Performed solely for instructional
purposes, using open-circuit, compressed-air SCUBA and conducted
within the no-decompression limits;
(ii) Performed solely for search, rescue, or related public safety purposes
by or under the control of a governmental agency; or
(iii) Governed by 45 CFR part 46 (Protection of Human Subjects, U.S. Department of Health and Human Services) or equivalent rules or regulations
established by another federal agency,
which regulate research, development,
or related purposes involving human
subjects.
(iv) Defined as scientific diving and
which is under the direction and control of a diving program containing at
least the following elements:
(A) Diving safety manual which includes at a minimum: Procedures covering all diving operations specific to
the program; procedures for emergency
care, including recompression and
evacuation; and criteria for diver training and certification.
(B) Diving control (safety) board,
with the majority of its members being
active divers, which shall at a minimum have the authority to: Approve
and monitor diving projects; review
and revise the diving safety manual;
assure compliance with the manual;
certify the depths to which a diver has
been trained; take disciplinary action
for unsafe practices; and, assure adherence to the buddy system (a diver is accompanied by and is in continuous contact with another diver in the water)
for SCUBA diving.
(3) Alternative requirements for recreational diving instructors and diving
guides. Employers of recreational diving instructors and diving guides are
not required to comply with the decompression-chamber
requirements
specified by paragraphs (b)(2) and
(c)(3)(iii) of § 1910.423 and paragraph
(b)(1) of § 1910.426 when they meet all of
the following conditions:
(i) The instructor or guide is engaging solely in recreational diving instruction or dive-guiding operations;
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| File Type | application/pdf |
| File Modified | 2014-08-16 |
| File Created | 2014-08-16 |