Electronic
Code of Federal Regulations
e-CFR
data is current as of December 29, 2017
|
|
|
Title
29: Labor
PART
1926—SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION
Subpart
K—Electrical
Authority:
Sections 6 and 8 of the Occupational Safety and Health Act of
1970 (29 U.S.C. 655 and 657); sec. 107, Contract Work Hours
and Safety Standards Act (40 U.S.C. 333); Secretary of Labor's
Order No. 9-83 (48 FR 35736) or 1-90 (55 FR 9033), as
applicable; 29 CFR part 1911.
Source:
51 FR 25318, July 11, 1986, unless otherwise noted.
General
§1926.400 Introduction.
This
subpart addresses electrical safety requirements that are
necessary for the practical safeguarding of employees involved
in construction work and is divided into four major divisions
and applicable definitions as follows:
(a)
Installation
safety requirements.
Installation safety requirements are contained in §§1926.402
through 1926.408. Included in this category are electric
equipment and installations used to provide electric power and
light on jobsites.
(b)
Safety-related
work practices.
Safety-related work practices are contained in §§1926.416
and 1926.417. In addition to covering the hazards arising from
the use of electricity at jobsites, these regulations also
cover the hazards arising from the accidental contact, direct
or indirect, by employees with all energized lines, above or
below ground, passing through or near the jobsite.
(c)
Safety-related
maintenance and environmental considerations.
Safety-related maintenance and environmental considerations
are contained in §§1926.431 and 1926.432.
(d)
Safety
requirements for special equipment.
Safety requirements for special equipment are contained in
§1926.441.
(e)
Definitions.
Definitions applicable to this subpart are contained in
§1926.449.
Back
to Top
§1926.401 [Reserved]
Back
to Top
Installation
Safety Requirements
Back
to Top
§1926.402 Applicability.
(a)
Covered.
Sections 1926.402 through 1926.408 contain installation safety
requirements for electrical equipment and installations used
to provide electric power and light at the jobsite. These
sections apply to installations, both temporary and permanent,
used on the jobsite; but these sections do not apply to
existing permanent installations that were in place before the
construction activity commenced.
Note:
If the electrical installation is made in accordance with the
National Electrical Code ANSI/NFPA 70-1984, exclusive of
Formal Interpretations and Tentative Interim Amendments, it
will be deemed to be in compliance with §§1926.403
through 1926.408, except for §§1926.404(b)(1) and
1926.405(a)(2)(ii) (E), (F), (G), and (J).
(b)
Not
covered.
Sections 1926.402 through 1926.408 do not cover installations
used for the generation, transmission, and distribution of
electric energy, including related communication, metering,
control, and transformation installations. (However, these
regulations do cover portable and vehicle-mounted generators
used to provide power for equipment used at the jobsite.) See
subpart V of this part for the construction of power
distribution and transmission lines.
Back
to Top
§1926.403 General
requirements.
(a)
Approval.
All electrical conductors and equipment shall be approved.
(b)
Examination,
installation, and use of equipment—(1)
Examination.
The employer shall ensure that electrical equipment is free
from recognized hazards that are likely to cause death or
serious physical harm to employees. Safety of equipment shall
be determined on the basis of the following considerations:
(i)
Suitability for installation and use in conformity with the
provisions of this subpart. Suitability of equipment for an
identified purpose may be evidenced by listing, labeling, or
certification for that identified purpose.
(ii)
Mechanical strength and durability, including, for parts
designed to enclose and protect other equipment, the adequacy
of the protection thus provided.
(iii)
Electrical insulation.
(iv)
Heating effects under conditions of use.
(v)
Arcing effects.
(vi)
Classification by type, size, voltage, current capacity,
specific use.
(vii)
Other factors which contribute to the practical safeguarding
of employees using or likely to come in contact with the
equipment.
(2)
Installation
and use.
Listed, labeled, or certified equipment shall be installed and
used in accordance with instructions included in the listing,
labeling, or certification.
(c)
Interrupting
rating.
Equipment intended to break current shall have an interrupting
rating at system voltage sufficient for the current that must
be interrupted.
(d)
Mounting
and cooling of equipment—(1)
Mounting.
Electric equipment shall be firmly secured to the surface on
which it is mounted. Wooden plugs driven into holes in
masonry, concrete, plaster, or similar materials shall not be
used.
(2)
Cooling.
Electrical equipment which depends upon the natural
circulation of air and convection principles for cooling of
exposed surfaces shall be installed so that room air flow 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. Electrical
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.
(e)
Splices.
Conductors shall be spliced or joined with splicing devices
designed for the use or by brazing, welding, or soldering with
a fusible metal or alloy. Soldered splices shall first be so
spliced or joined as to be mechanically and electrically
secure without solder and then soldered. All splices and
joints and the free ends of conductors shall be covered with
an insulation equivalent to that of the conductors or with an
insulating device designed for the purpose.
(f)
Arcing
parts.
Parts of electric equipment which in ordinary operation
produce arcs, sparks, flames, or molten metal shall be
enclosed or separated and isolated from all combustible
material.
(g)
Marking.
Electrical equipment shall not be used unless the
manufacturer's name, trademark, or other descriptive marking
by which the organization responsible for the product may be
identified is placed on the equipment and unless other
markings are provided giving voltage, current, wattage, or
other ratings as necessary. The marking shall be of sufficient
durability to withstand the environment involved.
(h)
Identification
of disconnecting means and circuits.
Each disconnecting means required by this subpart for motors
and appliances shall be legibly marked to indicate its
purpose, unless located and arranged so the purpose is
evident. Each service, feeder, and branch circuit, at its
disconnecting means or overcurrent device, shall be legibly
marked to indicate its purpose, unless located and arranged so
the purpose is evident. These markings shall be of sufficient
durability to withstand the environment involved.
(i)
600
Volts, nominal, or less.
This paragraph applies to equipment operating at 600 volts,
nominal, or less.
(1)
Working
space about electric equipment.
Sufficient access and working space shall be provided and
maintained about all electric equipment to permit ready and
safe operation and maintenance of such equipment.
(i)
Working
clearances.
Except as required or permitted elsewhere in this subpart, the
dimension of the working space in the direction of access to
live parts operating at 600 volts or less and likely to
require examination, adjustment, servicing, or maintenance
while alive shall not be less than indicated in Table K-1. In
addition to the dimensions shown in Table K-1, workspace shall
not be less than 30 inches (762 mm) wide in front of the
electric equipment. Distances shall be measured from the live
parts if they are exposed, or from the enclosure front or
opening if the live parts are enclosed. Walls constructed of
concrete, brick, or tile are considered to be grounded.
Working space is not required in back of assemblies such as
dead-front switchboards or motor control centers where there
are no renewable or adjustable parts such as fuses or switches
on the back and where all connections are accessible from
locations other than the back.
Table
K-1—Working Clearances
Nominal
voltage to ground
|
Minimum
clear distance for conditions1
|
(a)
|
(b)
|
(c)
|
|
Feet2
|
Feet2
|
Feet2
|
0-150
|
3
|
3
|
3
|
151-600
|
3
|
31⁄2
|
4
|
1Conditions
(a), (b), and (c) are as follows: (a) Exposed live parts on
one side and no live or grounded parts on the other side of
the working space, or exposed live parts on both sides
effectively guarded by insulating material. Insulated wire or
insulated busbars operating at not over 300 volts are not
considered live parts. (b) Exposed live parts on one side and
grounded parts on the other side. (c) Exposed live parts on
both sides of the workspace [not guarded as provided in
Condition (a)] with the operator between.
2Note:
For International System of Units (SI): one foot = 0.3048m.
(ii)
Clear
spaces.
Working space required by this subpart shall 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 guarded.
(iii)
Access
and entrance to working space.
At least one entrance shall be provided to give access to the
working space about electric equipment.
(iv)
Front
working space.
Where there are live parts normally exposed on the front of
switchboards or motor control centers, the working space in
front of such equipment shall not be less than 3 feet (914
mm).
(v)
Headroom.
The minimum headroom of working spaces about service
equipment, switchboards, panelboards, or motor control centers
shall be 6 feet 3 inches (1.91 m).
(2)
Guarding
of live parts.
(i) Except as required or permitted elsewhere in this subpart,
live parts of electric equipment operating at 50 volts or more
shall be guarded against accidental contact by cabinets or
other forms of 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 partitions or screens so arranged that only qualified
persons will have access to the space within reach of the live
parts. Any openings in such partitions or screens shall be so
sized and located that persons are not likely to come into
accidental contact with the live parts or to bring conducting
objects into contact with them.
(C)
By location on a balcony, gallery, or platform so elevated and
arranged as to exclude unqualified persons.
(D)
By elevation of 8 feet (2.44 m) or more above the floor or
other working surface and so installed as to exclude
unqualified persons.
(ii)
In locations where electric equipment would be exposed to
physical damage, enclosures or guards shall be so arranged and
of such strength as to prevent such damage.
(iii)
Entrances to rooms and other guarded locations containing
exposed live parts shall be marked with conspicuous warning
signs forbidding unqualified persons to enter.
(j)
Over
600 volts, nominal—(1)
General.
Conductors and equipment used on circuits exceeding 600 volts,
nominal, shall comply with all applicable provisions of
paragraphs (a) through (g) of this section and with the
following provisions which supplement or modify those
requirements. The provisions of paragraphs (j)(2), (j)(3), and
(j)(4) of this section do not apply to equipment on the supply
side of the service conductors.
(2)
Enclosure
for electrical installations.
Electrical installations in a vault, room, closet or in an
area surrounded by a wall, screen, or fence, access to which
is controlled by lock and key or other equivalent means, are
considered to be accessible to qualified persons only. A wall,
screen, or fence less than 8 feet (2.44 m) in height is not
considered adequate to prevent access unless it has other
features that provide a degree of isolation equivalent to an
8-foot (2.44-m) fence. The entrances to all buildings, rooms
or enclosures containing exposed live parts or exposed
conductors operating at over 600 volts, nominal, shall be kept
locked or shall be under the observation of a qualified person
at all times.
(i)
Installations
accessible to qualified persons only.
Electrical installations having exposed live parts shall be
accessible to qualified persons only and shall comply with the
applicable provisions of paragraph (j)(3) of this section.
(ii)
Installations
accessible to unqualified persons.
Electrical installations that are open to unqualified persons
shall be made with metal-enclosed equipment or shall be
enclosed in a vault or in an area, access to which is
controlled by a lock. Metal-enclosed switchgear, unit
substations, transformers, pull boxes, connection boxes, and
other similar associated equipment shall be marked with
appropriate caution signs. If equipment is exposed to physical
damage from vehicular traffic, guards shall be provided to
prevent such damage. Ventilating or similar openings in
metal-enclosed equipment shall be designed so that foreign
objects inserted through these openings will be deflected from
energized parts.
(3)
Workspace
about equipment.
Sufficient space shall be provided and maintained about
electric equipment to permit ready and safe operation and
maintenance of such equipment. Where energized parts are
exposed, the minimum clear workspace shall not be less than 6
feet 6 inches (1.98 m) high (measured vertically from the
floor or platform), or less than 3 feet (914 mm) wide
(measured parallel to the equipment). The depth shall be as
required in Table K-2. The workspace shall be adequate to
permit at least a 90-degree opening of doors or hinged panels.
(i)
Working
space.
The minimum clear working space in front of electric equipment
such as switchboards, control panels, switches, circuit
breakers, motor controllers, relays, and similar equipment
shall not be less than specified in Table K-2 unless otherwise
specified in this subpart. Distances shall be measured from
the live parts if they are exposed, or from the enclosure
front or opening if the live parts are enclosed. However,
working space is not required in back of equipment such as
deadfront switchboards or control assemblies where there are
no renewable or adjustable parts (such as fuses or switches)
on the back and where all connections are accessible from
locations other than the back. Where rear access is required
to work on de-energized parts on the back of enclosed
equipment, a minimum working space of 30 inches (762 mm)
horizontally shall be provided.
Table
K-2—Minimum Depth of Clear Working Space in Front of
Electric Equipment
Nominal
voltage to ground
|
Conditions1
|
(a)
|
(b)
|
(c)
|
|
Feet2
|
Feet2
|
Feet2
|
601
to 2,500
|
3
|
4
|
5
|
2,501
to 9,000
|
4
|
5
|
6
|
9,001
to 25,000
|
5
|
6
|
9
|
25,001
to 75 kV
|
6
|
8
|
10
|
Above
75kV
|
8
|
10
|
12
|
1Conditions
(a), (b), and (c) are as follows: (a) Exposed live parts on
one side and no live or grounded parts on the other side of
the working space, or exposed live parts on both sides
effectively guarded by insulating materials. Insulated wire or
insulated busbars operating at not over 300 volts are not
considered live parts. (b) Exposed live parts on one side and
grounded parts on the other side. Walls constructed of
concrete, brick, or tile are considered to be grounded
surfaces. (c) Exposed live parts on both sides of the
workspace [not guarded as provided in Condition (a)] with the
operator between.
2Note:
For SI units: one foot = 0.3048 m.
(ii)
Lighting
outlets and points of control.
The lighting outlets shall be so arranged that persons
changing lamps or making repairs on the lighting system will
not be endangered by live parts or other equipment. The points
of control shall be so located that persons are not likely to
come in contact with any live part or moving part of the
equipment while turning on the lights.
(iii)
Elevation
of unguarded live parts.
Unguarded live parts above working space shall be maintained
at elevations not less than specified in Table K-3.
Table
K-3—Elevation of Unguarded Energized Parts Above Working
Space
Nominal
voltage between phases
|
Minimum
elevation
|
601-7,500
|
8
feet 6 inches.1
|
7,501-35,000
|
9
feet.
|
Over
35kV
|
9
feet + 0.37 inches per kV above 35kV.
|
1Note:
For SI units: one inch = 25.4 mm; one foot = 0.3048 m.
(4)
Entrance
and access to workspace.
At least one entrance not less than 24 inches (610 mm) wide
and 6 feet 6 inches (1.98 m) high shall be provided to give
access to the working space about electric equipment. On
switchboard and control panels exceeding 48 inches (1.22 m) in
width, there shall be one entrance at each end of such board
where practicable. Where bare energized parts at any voltage
or insulated energized parts above 600 volts are located
adjacent to such entrance, they shall be guarded.
[51
FR 25318, July 11, 1986, as amended at 61 FR 5510, Feb. 13,
1996]
Back
to Top
§1926.404 Wiring
design and protection.
(a)
Use
and identification of grounded and grounding conductors—(1)
Identification
of conductors.
A conductor used as a grounded conductor shall be identifiable
and distinguishable from all other conductors. A conductor
used as an equipment grounding conductor shall be identifiable
and distinguishable from all other conductors.
(2)
Polarity
of connections.
No grounded conductor shall 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 shall not be used for
purposes other than grounding.
(b)
Branch
circuits—(1)
Ground-fault
protection—(i)
General.
The employer shall use either ground fault circuit
interrupters as specified in paragraph (b)(1)(ii) of this
section or an assured equipment grounding conductor program as
specified in paragraph (b)(1)(iii) of this section to protect
employees on construction sites. These requirements are in
addition to any other requirements for equipment grounding
conductors.
(ii)
Ground-fault
circuit interrupters.
All 120-volt, single-phase, 15- and 20-ampere receptacle
outlets on construction sites, which are not a part of the
permanent wiring of the building or structure and which are in
use by employees, shall have approved ground-fault circuit
interrupters for personnel protection. Receptacles on a
two-wire, single-phase portable or vehicle-mounted generator
rated not more than 5kW, where the circuit conductors of the
generator are insulated from the generator frame and all other
grounded surfaces, need not be protected with ground-fault
circuit interrupters.
(iii)
Assured
equipment grounding conductor program.
The employer shall establish and implement an assured
equipment grounding conductor program on construction sites
covering all cord sets, receptacles which are not a part of
the building or structure, and equipment connected by cord and
plug which are available for use or used by employees. This
program shall comply with the following minimum requirements:
(A)
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
and any affected employee.
(B)
The employer shall designate one or more competent persons (as
defined in §1926.32(f)) to implement the program.
(C)
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.
(D)
The following tests shall be performed on all cord sets,
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:
(1)
All equipment grounding conductors shall be tested for
continuity and shall be electrically continuous.
(2)
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.
(E)
All required tests shall be performed:
(1)
Before first use;
(2)
Before equipment is returned to service following any repairs;
(3)
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
(4)
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.
(F)
The employer shall not make available or permit the use by
employees of any equipment which has not met the requirements
of this paragraph (b)(1)(iii) of this section.
(G)
Tests performed as required in this paragraph 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.
(2)
Outlet
devices.
Outlet devices shall have an ampere rating not less than the
load to be served and shall comply with the following:
(i)
Single
receptacles.
A single receptacle installed on an individual branch circuit
shall have an ampere rating of not less than that of the
branch circuit.
(ii)
Two
or more receptacles.
Where connected to a branch circuit supplying two or more
receptacles or outlets, receptacle ratings shall conform to
the values listed in Table K-4.
(iii)
Receptacles
used for the connection of motors.
The rating of an attachment plug or receptacle used for cord-
and plug-connection of a motor to a branch circuit shall not
exceed 15 amperes at 125 volts or 10 amperes at 250 volts if
individual overload protection is omitted.
Table
K-4—Receptacle Ratings for Various Size Circuits
Circuit
rating amperes
|
Receptacle
rating amperes
|
15
|
Not
over 15.
|
20
|
15
or 20.
|
30
|
30.
|
40
|
40
or 50.
|
50
|
50.
|
(c)
Outside
conductors and lamps—(1)
600
volts, nominal, or less.
Paragraphs (c)(1)(i) through (c)(1)(iv) of this section apply
to branch circuit, feeder, and service conductors rated 600
volts, nominal, or less and run outdoors as open conductors.
(i)
Conductors
on poles.
Conductors supported on poles shall provide a horizontal
climbing space not less than the following:
(A)
Power conductors below communication conductors—30
inches (762 mm) .
(B)
Power conductors alone or above communication conductors: 300
volts or less—24 inches (610 mm); more than 300 volts—30
inches (762 mm).
(C)
Communication conductors below power conductors: with power
conductors 300 volts or less—24 inches (610 mm); more
than 300 volts—30 inches (762 mm).
(ii)
Clearance
from ground.
Open conductors shall conform to the following minimum
clearances:
(A)
10 feet (3.05 m)—above finished grade, sidewalks, or
from any platform or projection from which they might be
reached.
(B)
12 feet (3.66 m)—over areas subject to vehicular traffic
other than truck traffic.
(C)
15 feet (4.57 m)—over areas other than those specified
in paragraph (c)(1)(ii)(D) of this section that are subject to
truck traffic.
(D)
18 feet (5.49 m)—over public streets, alleys, roads, and
driveways.
(iii)
Clearance
from building openings.
Conductors shall have a clearance of at least 3 feet (914 mm)
from windows, doors, fire escapes, or similar locations.
Conductors run above the top level of a window are considered
to be out of reach from that window and, therefore, do not
have to be 3 feet (914 mm) away.
(iv)
Clearance
over roofs.
Conductors above roof space accessible to employees on foot
shall have a clearance from the highest point of the roof
surface of not less than 8 feet (2.44 m) vertical clearance
for insulated conductors, not less than 10 feet (3.05 m)
vertical or diagonal clearance for covered conductors, and not
less than 15 feet (4.57 m) for bare conductors, except that:
(A)
Where the roof space is also accessible to vehicular traffic,
the vertical clearance shall not be less than 18 feet (5.49
m), or
(B)
Where the roof space is not normally accessible to employees
on foot, fully insulated conductors shall have a vertical or
diagonal clearance of not less than 3 feet (914 mm), or
(C)
Where the voltage between conductors is 300 volts or less and
the roof has a slope of not less than 4 inches (102 mm) in 12
inches (305 mm), the clearance from roofs shall be at least 3
feet (914 mm), or
(D)
Where the voltage between conductors is 300 volts or less and
the conductors do not pass over more than 4 feet (1.22 m) of
the overhang portion of the roof and they are terminated at a
through-the-roof raceway or support, the clearance from roofs
shall be at least 18 inches (457 mm).
(2)
Location
of outdoor lamps.
Lamps for outdoor lighting shall be located below all live
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.
(d)
Services—(1)
Disconnecting
means—(i)
General.
Means shall be provided to disconnect all conductors in a
building or other structure from the service-entrance
conductors. The 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)
Simultaneous
opening of poles.
Each service disconnecting means shall simultaneously
disconnect all ungrounded conductors.
(2)
Services
over 600 volts, nominal.
The following additional requirements apply to services over
600 volts, nominal.
(i)
Guarding.
Service-entrance conductors installed as open wires shall be
guarded to make them accessible only to qualified persons.
(ii)
Warning
signs.
Signs warning of high voltage shall be posted where
unauthorized employees might come in contact with live parts.
(e)
Overcurrent
protection—(1)
600
volts, nominal, or less.
The following requirements apply to overcurrent protection of
circuits rated 600 volts, nominal, or less.
(i)
Protection
of conductors and equipment.
Conductors and equipment shall be protected from overcurrent
in accordance with their ability to safely conduct current.
Conductors shall have sufficient ampacity to carry the load.
(ii)
Grounded
conductors.
Except for motor-running overload protection, overcurrent
devices shall not interrupt the continuity of the grounded
conductor unless all conductors of the circuit are opened
simultaneously.
(iii)
Disconnection
of fuses and thermal cutouts.
Except for devices provided for current-limiting on the supply
side of the service disconnecting means, all cartridge fuses
which are accessible to other than qualified persons and all
fuses and thermal cutouts on circuits over 150 volts to ground
shall be provided with disconnecting means. This disconnecting
means shall be installed so that the fuse or thermal cutout
can be disconnected from its supply without disrupting service
to equipment and circuits unrelated to those protected by the
overcurrent device.
(iv)
Location
in or on premises.
Overcurrent devices shall be readily accessible. Overcurrent
devices shall not be located where they could create an
employee safety hazard by being exposed to physical damage or
located in the vicinity of easily ignitible material.
(v)
Arcing
or suddenly moving parts.
Fuses and circuit breakers shall be so located or shielded
that employees will not be burned or otherwise injured by
their operation.
(vi)
Circuit
breakers—(A)
Circuit breakers shall clearly indicate whether they are in
the open (off) or closed (on) position.
(B)
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.
(C)
If used as switches in 120-volt, fluorescent lighting
circuits, circuit breakers shall be marked “SWD.”
(2)
Over
600 volts, nominal.
Feeders and branch circuits over 600 volts, nominal, shall
have short-circuit protection.
(f)
Grounding.
Paragraphs (f)(1) through (f)(11) of this section contain
grounding requirements for systems, circuits, and equipment.
(1)
Systems
to be grounded.
The following systems which supply premises wiring shall be
grounded:
(i)
Three-wire
DC systems.
All 3-wire DC systems shall have their neutral conductor
grounded.
(ii)
Two-wire
DC systems.
Two-wire DC systems operating at over 50 volts through 300
volts between conductors shall be grounded unless they are
rectifier-derived from an AC system complying with paragraphs
(f)(1)(iii), (f)(1)(iv), and (f)(1)(v) of this section.
(iii)
AC
circuits, less than 50 volts.
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, 50 volts to 1000 volts.
AC systems of 50 volts to 1000 volts shall be grounded under
any of the following conditions, unless exempted by paragraph
(f)(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 480Y/277 volt, 3-phase,
4-wire in which the neutral is used as a circuit conductor;
(C)
If the system is nominally rated 240/120 volt, 3-phase, 4-wire
in which the midpoint of one phase is used as a circuit
conductor; or
(D)
If a service conductor is uninsulated.
(v)
Exceptions.
AC systems of 50 volts to 1000 volts are not required to be
grounded 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:
(A)
The system is used exclusively for control circuits,
(B)
The conditions of maintenance and supervision assure that only
qualified persons will service the installation,
(C)
Continuity of control power is required, and
(D)
Ground detectors are installed on the control system.
(2)
Separately
derived systems.
Where paragraph (f)(1) of this section requires grounding of
wiring systems whose power is derived from generator,
transformer, or converter windings and has no direct
electrical connection, including a solidly connected grounded
circuit conductor, to supply conductors originating in another
system, paragraph (f)(5) of this section shall also apply.
(3)
Portable
and vehicle-mounted generators—(i)
Portable
generators.
Under the following conditions, the frame of a portable
generator need not be grounded and may serve as the grounding
electrode for a system supplied by the generator:
(A)
The generator supplies only equipment mounted on the generator
and/or cord- and plug-connected equipment through receptacles
mounted on the generator, and
(B)
The noncurrent-carrying metal parts of equipment and the
equipment grounding conductor terminals of the receptacles are
bonded to the generator frame.
(ii)
Vehicle-mounted
generators.
Under the following conditions the frame of a vehicle may
serve as the grounding electrode for a system supplied by a
generator located on the vehicle:
(A)
The frame of the generator is bonded to the vehicle frame, and
(B)
The generator supplies only equipment located on the vehicle
and/or cord- and plug-connected equipment through receptacles
mounted on the vehicle or on the generator, and
(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 this section.
(iii)
Neutral
conductor bonding.
A neutral conductor shall be bonded to the generator frame if
the generator is a component of a separately derived system.
No other conductor need be bonded to the generator frame.
(4)
Conductors
to be grounded.
For AC premises wiring systems the identified conductor shall
be grounded.
(5)
Grounding
connections—(i)
Grounded
system.
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)
Ungrounded
systems.
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.
(6)
Grounding
path.
The path to ground from circuits, equipment, and enclosures
shall be permanent and continuous.
(7)
Supports,
enclosures, and equipment to be grounded—(i)
Supports
and enclosures for conductors.
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 25 feet (7.62 m);
(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)
Service
equipment enclosures.
Metal enclosures for service equipment shall be grounded.
(iii)
Fixed
equipment.
Exposed noncurrent-carrying metal parts of fixed equipment
which may become energized shall be grounded under any of the
following conditions:
(A)
If within 8 feet (2.44 m) vertically or 5 feet (1.52 m)
horizontally of ground or grounded metal objects and subject
to employee contact.
(B)
If located in a wet or damp location and subject to employee
contact.
(C)
If in electrical contact with metal.
(D)
If in a hazardous (classified) location.
(E)
If supplied by a metal-clad, metal-sheathed, or grounded metal
raceway wiring method.
(F)
If equipment operates with any terminal at over 150 volts to
ground; however, the following need not be grounded:
(1)
Enclosures for switches or circuit breakers used for other
than service equipment and accessible to qualified persons
only;
(2)
Metal frames of electrically heated appliances which are
permanently and effectively insulated from ground; and
(3)
The cases of distribution apparatus such as transformers and
capacitors mounted on wooden poles at a height exceeding 8
feet (2.44 m) above ground or grade level.
(iv)
Equipment
connected by cord and plug.
Under any of the conditions described in paragraphs
(f)(7)(iv)(A) through (f)(7)(iv)(C) of this section, exposed
noncurrent-carrying metal parts of cord- and plug-connected
equipment which may become energized shall be grounded:
(A)
If in a hazardous (classified) location (see §1926.407).
(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 one of the types listed in paragraphs
(f)(7)(iv)(C)(1)
through (f)(7)(iv)(C)(5)
of this section. However, even though the equipment may be one
of these types, it need not be grounded if it is exempted by
paragraph (f)(7)(iv)(C)(6).
(1)
Hand held motor-operated tools;
(2)
Cord- and plug-connected equipment 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;
(3)
Portable and mobile X-ray and associated equipment;
(4)
Tools likely to be used in wet and/or conductive locations;
and
(5)
Portable hand lamps.
(6)
Tools likely to be used in wet and/or conductive locations
need not be grounded if supplied through an isolating
transformer with an ungrounded secondary of not over 50 volts.
Listed or labeled portable tools and appliances protected by a
system of double insulation, or its equivalent, need not be
grounded. If such a system is employed, the equipment shall be
distinctively marked to indicate that the tool or appliance
utilizes a system of double insulation.
(v)
Nonelectrical
equipment.
The metal parts of the following nonelectrical equipment shall
be grounded: Frames and tracks of electrically operated
cranes; frames of nonelectrically driven elevator cars to
which electric conductors are attached; hand-operated metal
shifting ropes or cables of electric elevators, and metal
partitions, grill work, and similar metal enclosures around
equipment of over IkV between conductors.
(8)
Methods
of grounding equipment—(i)
With
circuit conductors.
Noncurrent-carrying metal parts of fixed equipment, if
required to be grounded by this subpart, shall be grounded by
an equipment grounding conductor which 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)
Grounding
conductor.
A conductor used for grounding fixed or movable equipment
shall have capacity to conduct safely any fault current which
may be imposed on it.
(iii)
Equipment
considered effectively grounded.
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
noncurrent-carrying metal parts of fixed equipment in
paragraph (f)(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.
(9)
Bonding.
If bonding conductors are used to assure electrical
continuity, they shall have the capacity to conduct any fault
current which may be imposed.
(10)
Made
electrodes.
If made electrodes are used, they shall be free from
nonconductive coatings, such as paint or enamel; and, if
practicable, they shall be embedded below permanent moisture
level. A single electrode consisting of a rod, pipe or plate
which has a resistance to ground greater than 25 ohms shall be
augmented by one additional electrode installed no closer than
6 feet (1.83 m) to the first electrode.
(11)
Grounding
of systems and circuits of 1000 volts and over (high
voltage)—(i)
General.
If high voltage systems are grounded, they shall comply with
all applicable provisions of paragraphs (f)(1) through (f)(10)
of this section as supplemented and modified by this paragraph
(f)(11).
(ii)
Grounding
of systems supplying portable or mobile equipment.
Systems supplying portable or mobile high voltage equipment,
other than substations installed on a temporary basis, shall
comply with the following:
(A)
Portable and mobile high voltage equipment shall be supplied
from a system having 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 de-energize any high voltage system component
which has developed a ground fault. The continuity of the
equipment grounding conductor shall be continuously monitored
so as to de-energize 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 or mobile
equipment system neutral impedance is connected shall be
isolated from and separated in the ground by at least 20 feet
(6.1 m) from any other system or equipment grounding
electrode, and there shall be no direct connection between the
grounding electrodes, such as buried pipe, fence or like
objects.
(iii)
Grounding
of equipment.
All noncurrent-carrying metal parts of portable equipment and
fixed equipment including their associated fences, housings,
enclosures, and supporting structures shall be grounded.
However, equipment which is guarded by location and isolated
from ground need not be grounded. Additionally, pole-mounted
distribution apparatus at a height exceeding 8 feet (2.44 m)
above ground or grade level need not be grounded.
[51
FR 25318, July 11, 1986, as amended at 54 FR 24334, June 7,
1989; 61 FR 5510, Feb. 13, 1996]
Back
to Top
§1926.405 Wiring
methods, components, and equipment for general use.
(a)
Wiring
methods.
The provisions of this paragraph do not apply to conductors
which form an integral part of equipment such as motors,
controllers, motor control centers and like equipment.
(1)
General
requirements—(i)
Electrical
continuity of metal raceways and enclosures.
Metal raceways, cable armor, and other metal enclosures for
conductors shall be metallically joined together into a
continuous electric conductor and shall be so connected to all
boxes, fittings, and cabinets as to provide effective
electrical continuity.
(ii)
Wiring
in ducts.
No wiring systems of any type shall be installed in ducts used
to transport dust, loose stock or flammable vapors. No wiring
system of any type shall be installed in any duct used for
vapor removal or in any shaft containing only such ducts.
(2)
Temporary
wiring—(i)
Scope.
The provisions of paragraph (a)(2) of this section apply to
temporary electrical power and lighting wiring methods which
may be of a class less than would be required for a permanent
installation. Except as specifically modified in paragraph
(a)(2) of this section, all other requirements of this subpart
for permanent wiring shall apply to temporary wiring
installations. Temporary wiring shall be removed immediately
upon completion of construction or the purpose for which the
wiring was installed.
(ii)
General
requirements for temporary wiring—(A)
Feeders shall originate in a distribution center. The
conductors shall be run as multiconductor cord or cable
assemblies or within raceways; or, where not subject to
physical damage, they may be run as open conductors on
insulators not more than 10 feet (3.05 m) apart.
(B)
Branch circuits shall originate in a power outlet or
panelboard. Conductors shall be run as multiconductor cord or
cable assemblies or open conductors, or shall be run in
raceways. All conductors shall be protected by overcurrent
devices at their ampacity. Runs of open conductors shall be
located where the conductors will not be subject to physical
damage, and the conductors shall be fastened at intervals not
exceeding 10 feet (3.05 m). No branch-circuit conductors shall
be laid on the floor. Each branch circuit that supplies
receptacles or fixed equipment shall contain a separate
equipment grounding conductor if the branch circuit is run as
open conductors.
(C)
Receptacles shall be of the grounding type. Unless installed
in a complete metallic raceway, each branch circuit shall
contain a separate equipment grounding conductor, and all
receptacles shall be electrically connected to the grounding
conductor. Receptacles for uses other than temporary lighting
shall not be installed on branch circuits which supply
temporary lighting. Receptacles shall not be connected to the
same ungrounded conductor of multiwire circuits which supply
temporary lighting.
(D)
Disconnecting switches or plug connectors shall be installed
to permit the disconnection of all ungrounded conductors of
each temporary circuit.
(E)
All lamps for general illumination shall be protected from
accidental contact or breakage. Metal-case sockets shall be
grounded.
(F)
Temporary lights shall not be suspended by their electric
cords unless cords and lights are designed for this means of
suspension.
(G)
Portable electric lighting used in wet and/or other conductive
locations, as for example, drums, tanks, and vessels, shall be
operated at 12 volts or less. However, 120-volt lights may be
used if protected by a ground-fault circuit interrupter.
(H)
A box shall be used wherever a change is made to a raceway
system or a cable system which is metal clad or metal
sheathed.
(I)
Flexible cords and cables shall be protected from damage.
Sharp corners and projections shall be avoided. Flexible cords
and cables may pass through doorways or other pinch points, if
protection is provided to avoid damage.
(J)
Extension cord sets used with portable electric tools and
appliances shall be of three-wire type and shall be designed
for hard or extra-hard usage. Flexible cords used with
temporary and portable lights shall be designed for hard or
extra-hard usage.
Note:
The National Electrical Code, ANSI/NFPA 70, in Article 400,
Table 400-4, lists various types of flexible cords, some of
which are noted as being designed for hard or extra-hard
usage. Examples of these types of flexible cords include hard
service cord (types S, ST, SO, STO) and junior hard service
cord (types SJ, SJO, SJT, SJTO).
(iii)
Guarding.
For temporary wiring over 600 volts, nominal, fencing,
barriers, or other effective means shall be provided to
prevent access of other than authorized and qualified
personnel.
(b)
Cabinets,
boxes, and fittings—(1)
Conductors
entering boxes, cabinets, or fittings.
Conductors entering boxes, cabinets, or fittings shall be
protected from abrasion, and openings through which conductors
enter shall be effectively closed. Unused openings in
cabinets, boxes, and fittings shall also be effectively
closed.
(2)
Covers
and canopies.
All pull boxes, junction boxes, and fittings shall be provided
with covers. If metal covers are used, they shall be grounded.
In energized installations each outlet box shall have a cover,
faceplate, or fixture canopy. Covers of outlet boxes having
holes through which flexible cord pendants pass shall be
provided with bushings designed for the purpose or shall have
smooth, well-rounded surfaces on which the cords may bear.
(3)
Pull
and junction boxes for systems over 600 volts, nominal.
In addition to other requirements in this section for pull and
junction boxes, the following shall apply to these boxes for
systems over 600 volts, nominal:
(i)
Complete
enclosure.
Boxes shall provide a complete enclosure for the contained
conductors or cables.
(ii)
Covers.
Boxes shall be closed by covers securely fastened in place.
Underground box covers that weigh over 100 pounds (43.6 kg)
meet this requirement. Covers for boxes shall be permanently
marked “HIGH VOLTAGE.” The marking shall be on the
outside of the box cover and shall be readily visible and
legible.
(c)
Knife
switches.
Single-throw knife switches shall be so connected that the
blades are dead when the switch is in the open position.
Single-throw knife switches shall be so placed that gravity
will not tend to close them. Single-throw knife switches
approved for use in the inverted position shall be provided
with a locking device that will ensure that the blades remain
in the open position when so set. Double-throw knife switches
may be mounted so that the throw will be either vertical or
horizontal. However, if the throw is vertical, a locking
device shall be provided to ensure that the blades remain in
the open position when so set.
(d)
Switchboards
and panelboards.
Switchboards that have any exposed live parts shall be located
in permanently dry locations and accessible only to qualified
persons. Panelboards shall be mounted in cabinets, cutout
boxes, or enclosures 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. Exposed blades of knife switches shall
be dead when open.
(e)
Enclosures
for damp or wet locations—(1)
Cabinets,
fittings, and boxes.
Cabinets, cutout boxes, fittings, boxes, and panelboard
enclosures in damp or wet locations shall be installed so as
to prevent moisture or water from entering and accumulating
within the enclosures. In wet locations the enclosures shall
be weatherproof.
(2)
Switches
and circuit breakers.
Switches, circuit breakers, and switchboards installed in wet
locations shall be enclosed in weatherproof enclosures.
(f)
Conductors
for general wiring.
All conductors used for general wiring shall be insulated
unless otherwise permitted in this subpart. The conductor
insulation shall be of a type that is suitable for the
voltage, operating temperature, and location of use. Insulated
conductors shall be distinguishable by appropriate color or
other means as being grounded conductors, ungrounded
conductors, or equipment grounding conductors.
(g)
Flexible
cords and cables—(1)
Use
of flexible cords and cables—(i)
Permitted
uses.
Flexible cords and cables shall be suitable for conditions of
use and location. Flexible cords and cables shall be used only
for:
(A)
Pendants;
(B)
Wiring of fixtures;
(C)
Connection of portable lamps or appliances;
(D)
Elevator cables;
(E)
Wiring of cranes and hoists;
(F)
Connection of stationary equipment to facilitate their
frequent interchange;
(G)
Prevention of the transmission of noise or vibration; or
(H)
Appliances where the fastening means and mechanical
connections are designed to permit removal for maintenance and
repair.
(ii)
Attachment
plugs for cords.
If used as permitted in paragraphs (g)(1)(i)(C), (g)(1)(i)(F),
or (g)(1)(i)(H) of this section, the flexible cord shall be
equipped with an attachment plug and shall be energized from a
receptacle outlet.
(iii)
Prohibited
uses.
Unless necessary for a use permitted in paragraph (g)(1)(i) of
this section, flexible cords and cables shall 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,
except as permitted in paragraph (a)(2)(ii)(1) of this
section;
(D)
Where attached to building surfaces; or
(E)
Where concealed behind building walls, ceilings, or floors.
(2)
Identification,
splices, and terminations—(i)
Identification.
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.
(ii)
Marking.
Type SJ, SJO, SJT, SJTO, S, SO, ST, and STO cords shall not be
used unless durably marked on the surface with the type
designation, size, and number of conductors.
(iii)
Splices.
Flexible cords shall be used only in continuous lengths
without splice or tap. Hard service flexible cords No. 12 or
larger may be repaired if spliced so that the splice retains
the insulation, outer sheath properties, and usage
characteristics of the cord being spliced.
(iv)
Strain
relief.
Flexible cords shall be connected to devices and fittings so
that strain relief is provided which will prevent pull from
being directly transmitted to joints or terminal screws.
(v)
Cords
passing through holes.
Flexible cords and cables shall be protected by bushings or
fittings where passing through holes in covers, outlet boxes,
or similar enclosures.
(h)
Portable
cables over 600 volts, nominal.
Multiconductor portable cable for use in supplying power to
portable or mobile equipment at over 600 volts, nominal, shall
consist of No. 8 or larger conductors employing flexible
stranding. Cables operated at over 2000 volts shall be
shielded for the purpose of confining the voltage stresses to
the insulation. Grounding conductors shall be provided.
Connectors for these cables shall be of a locking type with
provisions to prevent their opening or closing while
energized. Strain relief shall be provided at connections and
terminations. Portable cables shall not be operated with
splices unless the splices are of the permanent molded,
vulcanized, or other equivalent type. Termination enclosures
shall be marked with a high voltage hazard warning, and
terminations shall be accessible only to authorized and
qualified personnel.
(i)
Fixture
wires—(1)
General.
Fixture wires shall be suitable for the voltage, temperature,
and location of use. A fixture wire which is used as a
grounded conductor shall be identified.
(2)
Uses
permitted.
Fixture wires may be used:
(i)
For installation in lighting, fixtures and in similar
equipment where enclosed or protected and not subject to
bending or twisting in use; or
(ii)
For connecting lighting fixtures to the branch-circuit
conductors supplying the fixtures.
(3)
Uses
not permitted.
Fixture wires shall not be used as branch-circuit conductors
except as permitted for Class 1 power-limited circuits.
(j)
Equipment
for general use—(1)
Lighting
fixtures, lampholders, lamps, and receptacles—(i)
Live
parts.
Fixtures, lampholders, lamps, rosettes, and receptacles shall
have no live parts normally exposed to employee contact.
However, rosettes and cleat-type lampholders and receptacles
located at least 8 feet (2.44 m) above the floor may have
exposed parts.
(ii)
Support.
Fixtures, lampholders, rosettes, and receptacles shall be
securely supported. A fixture that weighs more than 6 pounds
(2.72 kg) or exceeds 16 inches (406 mm) in any dimension shall
not be supported by the screw shell of a lampholder.
(iii)
Portable
lamps.
Portable lamps shall be wired with flexible cord and an
attachment plug of the polarized or grounding type. If the
portable lamp uses an Edison-based lampholder, the grounded
conductor shall be identified and attached to the screw shell
and the identified blade of the attachment plug. In addition,
portable handlamps shall comply with the following:
(A)
Metal shell, paperlined lampholders shall not be used;
(B)
Handlamps shall be equipped with a handle of molded
composition or other insulating material;
(C)
Handlamps shall be equipped with a substantial guard attached
to the lampholder or handle;
(D)
Metallic guards shall be grounded by the means of an equipment
grounding conductor run within the power supply cord.
(iv)
Lampholders.
Lampholders of the screw-shell type shall be installed for use
as lampholders only. Lampholders installed in wet or damp
locations shall be of the weatherproof type.
(v)
Fixtures.
Fixtures installed in wet or damp locations shall be
identified for the purpose and shall be installed so that
water cannot enter or accumulate in wireways, lampholders, or
other electrical parts.
(2)
Receptacles,
cord connectors, and attachment plugs (caps)—(i)
Configuration.
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.
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.
(ii)
Damp
and wet locations.
A receptacle installed in a wet or damp location shall be
designed for the location.
(3)
Appliances—(i)
Live
parts.
Appliances, other than those in which the current-carrying
parts at high temperatures are necessarily exposed, shall have
no live parts normally exposed to employee contact.
(ii)
Disconnecting
means.
A means shall be provided to disconnect each appliance.
(iii)
Rating.
Each appliance shall be marked with its rating in volts and
amperes or volts and watts.
(4)
Motors.
This paragraph applies to motors, motor circuits, and
controllers.
(i)
In
sight from.
If specified that one piece of equipment shall be “in
sight from” another piece of equipment, one shall be
visible and not more than 50 feet (15.2 m) from the other.
(ii)
Disconnecting
means—(A)
A disconnecting means shall be located in sight from the
controller location. The controller disconnecting means for
motor branch circuits over 600 volts, nominal, may be out of
sight of the controller, if the controller is marked with a
warning label giving the location and identification of the
disconnecting means which is to be locked in the open
position.
(B)
The disconnecting means shall disconnect the motor and the
controller from all ungrounded supply conductors and shall be
so designed that no pole can be operated independently.
(C)
If a motor and the driven machinery are not in sight from the
controller location, the installation shall comply with one of
the following conditions:
(1)
The controller disconnecting means shall be capable of being
locked in the open position.
(2)
A manually operable switch that will disconnect the motor from
its source of supply shall be placed in sight from the motor
location.
(D)
The disconnecting means shall plainly indicate whether it is
in the open (off) or closed (on) position.
(E)
The disconnecting means shall be readily accessible. If more
than one disconnect is provided for the same equipment, only
one need be readily accessible.
(F)
An individual disconnecting means shall be provided for each
motor, but a single disconnecting means may be used for a
group of motors under any one of the following conditions:
(1)
If a number of motors drive special parts of a single machine
or piece of apparatus, such as a metal or woodworking machine,
crane, or hoist;
(2)
If a group of motors is under the protection of one set of
branch-circuit protective devices; or
(3)
If a group of motors is in a single room in sight from the
location of the disconnecting means.
(iii)
Motor
overload, short-circuit, and ground-fault protection.
Motors, 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.
(iv)
Protection
of live parts—all voltages—(A)
Stationary motors having commutators, collectors, and brush
rigging located inside of motor end brackets and not
conductively connected to supply circuits operating at more
than 150 volts to ground need not have such parts guarded.
Exposed live parts of motors and controllers operating at 50
volts or more between terminals shall be guarded against
accidental contact by any of the following:
(1)
By installation in a room or enclosure that is accessible only
to qualified persons;
(2)
By installation on a balcony, gallery, or platform, so
elevated and arranged as to exclude unqualified persons; or
(3)
By elevation 8 feet (2.44 m) or more above the floor.
(B)
Where live parts of motors or controllers operating at over
150 volts to ground are guarded against accidental contact
only by location, and where adjustment or other attendance may
be necessary during the operation of the apparatus, 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)
Application.
The following paragraphs cover the installation of all
transformers, except:
(A)
Current transformers;
(B)
Dry-type transformers installed as a component part of other
apparatus;
(C)
Transformers which are an integral part of an X-ray, high
frequency, or electrostatic-coating apparatus;
(D)
Transformers used with Class 2 and Class 3 circuits, sign and
outline lighting, electric discharge lighting, and
power-limited fire-protective signaling circuits.
(ii)
Operating
voltage.
The operating voltage of exposed live parts of transformer
installations shall be indicated by warning signs or visible
markings on the equipment or structure.
(iii)
Transformers
over 35 kV.
Dry-type, high fire point liquid-insulated, and
askarel-insulated transformers installed indoors and rated
over 35 kV shall be in a vault.
(iv)
Oil-insulated
transformers.
If they present a fire hazard to employees, oil-insulated
transformers installed indoors shall be in a vault.
(v)
Fire
protection.
Combustible material, combustible buildings and parts of
buildings, fire escapes, and door and window openings shall be
safeguarded from fires which may originate in oil-insulated
transformers attached to or adjacent to a building or
combustible material.
(vi)
Transformer
vaults.
Transformer vaults shall be constructed so as to contain fire
and combustible liquids within the vault and to prevent
unauthorized access. Locks and latches shall be so arranged
that a vault door can be readily opened from the inside.
(vii)
Pipes
and ducts.
Any pipe or duct system foreign to the vault installation
shall not enter or pass through a transformer vault.
(viii)
Material
storage.
Materials shall not be stored in transformer vaults.
(6)
Capacitors—(i)
Drainage
of stored charge.
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 and
maintaining the discharged state after the capacitor is
disconnected from its source of supply.
(ii)
Over
600 volts.
Capacitors rated over 600 volts, nominal, shall comply with
the following additional requirements:
(A)
Isolating or disconnecting switches (with no interrupting
rating) shall be interlocked with the load interrupting device
or shall be provided with prominently displayed caution signs
to prevent switching load current.
(B)
For series capacitors the proper switching shall be assured by
use of at least one of the following:
(1)
Mechanically sequenced isolating and bypass switches,
(2)
Interlocks, or
(3)
Switching procedure prominently displayed at the switching
location.
[51
FR 25318, July 11, 1986, as amended at 61 FR 5510, Feb. 13,
1996]
Back
to Top
§1926.406 Specific
purpose equipment and installations.
(a)
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—(i)
Runway
conductor disconnecting means.
A readily accessible disconnecting means shall be provided
between the runway contact conductors and the power supply.
(ii)
Disconnecting
means for cranes and monorail hoists.
A disconnecting means, capable of being locked in the open
position, shall be provided in the leads from the runway
contact conductors or other power supply on any crane or
monorail hoist.
(A)
If this additional disconnecting means is not readily
accessible from the crane or monorail hoist operating station,
means shall be provided at the operating station to open the
power circuit to all motors of the crane or monorail hoist.
(B)
The additional disconnect may be omitted if a monorail hoist
or hand-propelled crane bridge installation meets all of the
following:
(1)
The unit is floor controlled;
(2)
The unit is within view of the power supply disconnecting
means; and
(3)
No fixed work platform has been provided for servicing the
unit.
(2)
Control.
A limit switch or other device shall be provided to prevent
the load block from passing the safe upper limit of travel of
any hoisting mechanism.
(3)
Clearance.
The dimension of the working space in the direction of access
to live parts which may require examination, adjustment,
servicing, or maintenance while alive shall be a minimum of 2
feet 6 inches (762 mm). Where controls are enclosed in
cabinets, the door(s) shall open at least 90 degrees or be
removable, or the installation shall provide equivalent
access.
(4)
Grounding.
All exposed metal parts of cranes, monorail hoists, hoists and
accessories including pendant controls shall be metallically
joined together into a continuous electrical conductor so that
the entire crane or hoist will be grounded in accordance with
§1926.404(f). Moving parts, other than removable
accessories or attachments, having metal-to-metal bearing
surfaces shall be considered to be electrically connected to
each other through the bearing surfaces for grounding
purposes. The trolley frame and bridge frame shall be
considered as electrically grounded through the bridge and
trolley wheels and its respective tracks unless conditions
such as paint or other insulating materials prevent reliable
metal-to-metal contact. In this case a separate bonding
conductor shall be provided.
(b)
Elevators,
escalators, and moving walks—(1)
Disconnecting
means.
Elevators, escalators, and moving walks shall have a single
means for disconnecting all ungrounded main power supply
conductors for each unit.
(2)
Control
panels.
If control panels are not located in the same space as the
drive machine, they shall be located in cabinets with doors or
panels capable of being locked closed.
(c)
Electric
welders—disconnecting means—(1)
Motor-generator,
AC transformer, and DC rectifier arc welders.
A disconnecting means shall be provided in the supply circuit
for each motor-generator arc welder, and for each AC
transformer and DC rectifier arc welder which is not equipped
with a disconnect mounted as an integral part of the welder.
(2)
Resistance
welders.
A switch or circuit breaker shall be provided by which each
resistance welder and its control equipment can be isolated
from the supply circuit. The ampere rating of this
disconnecting means shall not be less than the supply
conductor ampacity.
(d)
X-Ray
equipment—(1)
Disconnecting
means—(i)
General.
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)
More
than one piece of equipment.
If more than one piece of equipment is operated from the same
high-voltage circuit, each piece or each group of equipment as
a unit shall be provided with a high-voltage switch or
equivalent disconnecting means. This disconnecting means shall
be constructed, enclosed, or located so as to avoid contact by
employees with its live parts.
(2)
Control—Radiographic
and fluoroscopic types.
Radiographic and fluoroscopic-type equipment shall be
effectively enclosed or shall have interlocks that deenergize
the equipment automatically to prevent ready access to live
current-carrying parts.
§1926.407 Hazardous
(classified) locations.
(a)
Scope.
This section sets forth requirements for electric equipment
and wiring in locations which are classified depending on the
properties of the flammable vapors, liquids or gases, or
combustible dusts or fibers which may be present therein and
the likelihood that a flammable or combustible concentration
or quantity is present. Each room, section or area shall be
considered individually in determining its classification.
These hazardous (classified) locations are assigned six
designations as follows:
Class
I, Division 1
Class
I, Division 2
Class
II, Division 1
Class
II, Division 2
Class
III, Division l
Class
III, Division 2
For
definitions of these locations see §1926.449. All
applicable requirements in this subpart apply to all hazardous
(classified) locations, unless modified by provisions of this
section.
(b)
Electrical
installations.
Equipment, wiring methods, and installations of equipment in
hazardous (classified) locations shall be approved as
intrinsically safe or 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 included
in its listing or labeling.
(2)
Approved
for the hazardous (classified) location—(i)
General.
Equipment shall be approved not only for the class of location
but also for the ignitible or combustible properties of the
specific gas, vapor, dust, or fiber that will be present.
Note:
NFPA 70, the National Electrical Code, lists or defines
hazardous gases, vapors, and dusts by “Groups”
characterized by their ignitible or combustible properties.
(ii)
Marking.
Equipment shall not be used unless it is 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 shall not exceed the
ignition temperature of the specific gas, vapor, or dust to be
encountered. However, the following provisions modify this
marking requirement for specific equipment:
(A)
Equipment of the non-heat-producing type (such as junction
boxes, conduit, and fitting) and equipment of the
heat-producing type having a maximum temperature of not more
than 100 degrees C (212 degrees F) need not have a marked
operating temperature or temperature range.
(B)
Fixed lighting fixtures marked for use only in Class I,
Division 2 locations need not be marked to indicate the group.
(C)
Fixed general-purpose equipment in Class I locations, other
than lighting fixtures, which is acceptable for use in Class
I, Division 2 locations need not be marked with the class,
group, division, or operating temperature.
(D)
Fixed dust-tight equipment, other than lighting fixtures,
which is acceptable for use in Class II, Division 2 and Class
III locations need not be marked with the class, group,
division, or operating temperature.
(3)
Safe
for the hazardous (classified) location.
Equipment which is safe for the location shall be of a type
and design which the employer demonstrates will provide
protection from the hazards arising from the combustibility
and flammability of vapors, liquids, gases, dusts, or fibers.
Note:
The National Electrical Code, NFPA 70, contains guidelines for
determining the type and design of equipment and installations
which will meet this requirement. The guidelines of this
document address electric wiring, equipment, and systems
installed in hazardous (classified) locations and contain
specific provisions for the following: wiring methods, wiring
connections, conductor insulation, flexible cords, sealing and
drainage, transformers, capacitors, switches, circuit
breakers, fuses, motor controllers, receptacles, attachment
plugs, meters, relays, instruments, resistors, generators,
motors, lighting fixtures, storage battery charging equipment,
electric cranes, electric hoists and similar equipment,
utilization equipment, signaling systems, alarm systems,
remote control systems, local loud speaker and communication
systems, ventilation piping, live parts, lightning surge
protection, and grounding. Compliance with these guidelines
will constitute one means, but not the only means, of
compliance with this paragraph.
(c)
Conduits.
All conduits shall be threaded and shall be made wrench-tight.
Where it is impractical to make a threaded joint tight, a
bonding jumper shall be utilized.
[51
FR 25318, July 11, 1986, as amended at 61 FR 5510, Feb. 13,
1996]
§1926.408 Special
systems.
(a)
Systems
over 600 volts, nominal.
Paragraphs (a)(1) through (a)(4) of this section contain
general requirements for all circuits and equipment operated
at over 600 volts.
(1)
Wiring
methods for fixed installations—(i)
Above
ground.
Above-ground conductors shall be installed in rigid metal
conduit, in intermediate metal conduit, in cable trays, in
cablebus, in other suitable raceways, or as open runs of
metal-clad cable designed for the use and purpose. However,
open runs of non-metallic-sheathed cable or of bare conductors
or busbars may be installed in locations which are accessible
only to qualified persons. Metallic shielding components, such
as tapes, wires, or braids for conductors, shall be grounded.
Open runs of insulated wires and cables having a bare lead
sheath or a braided outer covering shall be supported in a
manner designed to prevent physical damage to the braid or
sheath.
(ii)
Installations
emerging from the ground.
Conductors emerging from the ground shall be enclosed in
raceways. Raceways installed on poles shall be of rigid metal
conduit, intermediate metal conduit, PVC schedule 80 or
equivalent extending from the ground line up to a point 8 feet
(2.44 m) above finished grade. Conductors entering a building
shall be protected by an enclosure from the ground line to the
point of entrance. Metallic enclosures shall be grounded.
(2)
Interrupting
and isolating devices—(i)
Circuit
breakers.
Circuit breakers located indoors shall consist of
metal-enclosed or fire-resistant, cell-mounted units. In
locations accessible only to qualified personnel, open
mounting of circuit breakers is permitted. A means of
indicating the open and closed position of circuit breakers
shall be provided.
(ii)
Fused
cutouts.
Fused cutouts installed in buildings or transformer vaults
shall be of a type identified for the purpose. They shall be
readily accessible for fuse replacement.
(iii)
Equipment
isolating means.
A means shall be provided to completely isolate equipment for
inspection and repairs. Isolating means which are not designed
to interrupt the load current of the circuit shall be either
interlocked with a circuit interrupter or provided with a sign
warning against opening them under load.
(3)
Mobile
and portable equipment—(i)
Power
cable connections to mobile machines.
A metallic enclosure shall be provided on the mobile machine
for enclosing the terminals of the power cable. The enclosure
shall include provisions for a solid connection for the ground
wire(s) terminal to ground effectively the machine frame. The
method of cable termination used shall prevent any strain or
pull on the cable from stressing the electrical connections.
The enclosure shall have provision for locking so only
authorized qualified persons may open it and shall be marked
with a sign warning of the presence of energized parts.
(ii)
Guarding
live parts.
All energized switching and control parts shall be enclosed in
effectively grounded metal cabinets or enclosures. Circuit
breakers and protective equipment shall have the operating
means projecting through the metal cabinet or enclosure so
these units can be reset without locked doors being opened.
Enclosures and metal cabinets shall be locked so that only
authorized qualified persons have access and shall be marked
with a sign warning of the presence of energized parts.
Collector ring assemblies on revolving-type machines (shovels,
draglines, etc.) shall be guarded.
(4)
Tunnel
installations—(i)
Application.
The provisions of this paragraph apply to installation and use
of high-voltage power distribution and utilization equipment
which is associated with tunnels and which is portable and/or
mobile, such as substations, trailers, cars, mobile shovels,
draglines, hoists, drills, dredges, compressors, pumps,
conveyors, and underground excavators.
(ii)
Conductors.
Conductors in tunnels shall be installed in one or more of the
following:
(A)
Metal conduit or other metal raceway,
(B)
Type MC cable, or
(C)
Other suitable multiconductor cable.
Conductors
shall also be so located or guarded as to protect them from
physical damage. Multiconductor portable cable may supply
mobile equipment. An equipment grounding conductor shall be
run with circuit conductors inside the metal raceway or inside
the multiconductor cable jacket. The equipment grounding
conductor may be insulated or bare.
(iii)
Guarding
live parts.
Bare terminals of transformers, switches, motor controllers,
and other equipment shall be enclosed to prevent accidental
contact with energized parts. Enclosures for use in tunnels
shall be drip-proof, weatherproof, or submersible as required
by the environmental conditions.
(iv)
Disconnecting
means.
A disconnecting means that simultaneously opens all ungrounded
conductors shall be installed at each transformer or motor
location.
(v)
Grounding
and bonding.
All nonenergized metal parts of electric equipment and metal
raceways and cable sheaths shall be grounded and bonded to all
metal pipes and rails at the portal and at intervals not
exceeding 1000 feet (305 m) throughout the tunnel.
(b)
Class
1, Class 2, and Class 3 remote control, signaling, and
power-limited circuits—(1)
Classification.
Class 1, Class 2, or Class 3 remote control, signaling, or
power-limited circuits are characterized by their usage and
electrical power limitation which differentiates them from
light and power circuits. These circuits are classified in
accordance with their respective voltage and power limitations
as summarized in paragraphs (b)(1)(i) through (b)(1)(iii) of
this section.
(i)
Class
1 circuits—(A)
A Class 1 power-limited circuit is supplied from a source
having a rated output of not more than 30 volts and 1000
volt-amperes.
(B)
A Class 1 remote control circuit or a Class 1 signaling
circuit has a voltage which does not exceed 600 volts;
however, the power output of the source need not be limited.
(ii)
Class
2 and Class 3 circuits—(A)
Power for Class 2 and Class 3 circuits is limited either
inherently (in which no overcurrent protection is required) or
by a combination of a power source and overcurrent protection.
(B)
The maximum circuit voltage is 150 volts AC or DC for a Class
2 inherently limited power source, and 100 volts AC or DC for
a Class 3 inherently limited power source.
(C)
The maximum circuit voltage is 30 volts AC and 60 volts DC for
a Class 2 power source limited by overcurrent protection, and
150 volts AC or DC for a Class 3 power source limited by
overcurrent protection.
(iii)
Application.
The maximum circuit voltages in paragraphs (b)(1)(i) and
(b)(1)(ii) of this section apply to sinusoidal AC or
continuous DC power sources, and where wet contact occurrence
is not likely.
(2)
Marking.
A Class 2 or Class 3 power supply unit shall not be used
unless it is durably marked where plainly visible to indicate
the class of supply and its electrical rating.
(c)
Communications
systems—(1)
Scope.
These provisions for communication systems apply to such
systems as central-station-connected and
non-central-station-connected telephone circuits, radio
receiving and transmitting equipment, and outside wiring for
fire and burglar alarm, and similar central station systems.
These installations need not comply with the provisions of
§§1926.403 through 1926.408(b), except
§1926.404(c)(1)(ii) and §1926.407.
(2)
Protective
devices—(i)
Circuits
exposed to power conductors.
Communication circuits so located as to be exposed to
accidental contact with light or power conductors operating at
over 300 volts shall have each circuit so exposed provided
with an approved protector.
(ii)
Antenna
lead-ins.
Each conductor of a lead-in from an outdoor antenna shall be
provided with an antenna discharge unit or other means that
will drain static charges from the antenna system.
(3)
Conductor
location—(i)
Outside
of buildings—(A)
Receiving distribution lead-in or aerial-drop cables attached
to buildings and lead-in conductors to radio transmitters
shall be so installed as to avoid the possibility of
accidental contact with electric light or power conductors.
(B)
The clearance between lead-in conductors and any lightning
protection conductors shall not be less than 6 feet (1.83 m).
(ii)
On
poles.
Where practicable, communication conductors on poles shall be
located below the light or power conductors. Communications
conductors shall not be attached to a crossarm that carries
light or power conductors.
(iii)
Inside
of buildings.
Indoor antennas, lead-ins, and other communication conductors
attached as open conductors to the inside of buildings shall
be located at least 2 inches (50.8 mm) from conductors of any
light or power or Class 1 circuits unless a special and
equally protective method of conductor separation is employed.
(4)
Equipment
location.
Outdoor metal structures supporting antennas, as well as
self-supporting antennas such as vertical rods or dipole
structures, shall be located as far away from overhead
conductors of electric light and power circuits of over 150
volts to ground as necessary to avoid the possibility of the
antenna or structure falling into or making accidental contact
with such circuits.
(5)
Grounding—(i)
Lead-in
conductors.
If exposed to contact with electric light or 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.
(ii)
Antenna
structures.
Masts and metal structures supporting antennas shall be
permanently and effectively grounded without splice or
connection in the grounding conductor.
(iii)
Equipment
enclosures.
Transmitters shall be enclosed in a metal frame or grill or
separated from the operating space by a barrier, all metallic
parts of which are effectively connected to ground. All
external metal handles and controls accessible to the
operating personnel shall be effectively grounded. Unpowered
equipment and enclosures shall be considered grounded where
connected to an attached coaxial cable with an effectively
grounded metallic shield.
[51
FR 25318, July 11, 1986, as amended at 61 FR 5510, Feb. 13,
1996]
§§1926.409-1926.415 [Reserved]
Safety-Related
Work Practices
§1926.416 General
requirements.
(a)
Protection
of employees—(1)
No employer shall permit an employee to work in such proximity
to any part of an electric power circuit that the employee
could contact the electric power circuit in the course of
work, unless the employee is protected against electric shock
by deenergizing the circuit and grounding it or by guarding it
effectively by insulation or other means.
(2)
In work areas where the exact location of underground electric
powerlines is unknown, employees using jack-hammers, bars, or
other hand tools which may contact a line shall be provided
with insulated protective gloves.
(3)
Before work is begun the employer shall ascertain by inquiry
or direct observation, or by instruments, whether any part of
an energized electric power circuit, exposed or concealed, is
so located that the performance of the work may bring any
person, tool, or machine into physical or electrical contact
with the electric power circuit. The employer shall post and
maintain proper warning signs where such a circuit exists. The
employer shall advise employees of the location of such lines,
the hazards involved, and the protective measures to be taken.
(b)
Passageways
and open spaces—-(1)
Barriers or other means of guarding shall be provided to
ensure that workspace for electrical equipment will not be
used as a passageway during periods when energized parts of
electrical equipment are exposed.
(2)
Working spaces, walkways, and similar locations shall be kept
clear of cords so as not to create a hazard to employees.
(c)
Load
ratings.
In existing installations, no changes in circuit protection
shall be made to increase the load in excess of the load
rating of the circuit wiring.
(d)
Fuses.
When fuses are installed or removed with one or both terminals
energized, special tools insulated for the voltage shall be
used.
(e)
Cords
and cables.
(1) Worn or frayed electric cords or cables shall not be used.
(2)
Extension cords shall not be fastened with staples, hung from
nails, or suspended by wire.
[44
FR 8577, Feb. 9, 1979; 44 FR 20940, Apr. 6, 1979, as amended
at 55 FR 42328, Oct. 18, 1990; 58 FR 35179, June 30, 1993; 61
FR 9251, Mar. 7, 1996; 61 FR 41738, Aug. 12, 1996]
Back
to Top
§1926.417 Lockout
and tagging of circuits.
(a)
Controls.
Controls that are to be deactivated during the course of work
on energized or deenergized equipment or circuits shall be
tagged.
(b)
Equipment
and circuits.
Equipment or circuits that are deenergized shall be rendered
inoperative and shall have tags attached at all points where
such equipment or circuits can be energized.
(c)
Tags.
Tags shall be placed to identify plainly the equipment or
circuits being worked on.
[44
FR 8577, Feb. 9, 1979; 44 FR 20940, Apr. 6, 1979, as amended
at 55 FR 42328, Oct. 18, 1990; 58 FR 35181, June 30, 1993; 61
FR 9251, Mar. 7, 1996; 61 FR 41739, Aug. 12, 1996]]
§§1926.418-1926.430 [Reserved]
Safety-Related
Maintenance and Environmental Considerations
§1926.431 Maintenance
of equipment.
The
employer shall ensure that all wiring components and
utilization equipment in hazardous locations are maintained in
a dust-tight, dust-ignition-proof, or explosion-proof
condition, as appropriate. There shall be no loose or missing
screws, gaskets, threaded connections, seals, or other
impairments to a tight condition.
§1926.432 Environmental
deterioration of equipment.
(a)
Deteriorating
agents—(1)
Unless identified for use in the operating environment, no
conductors or equipment shall be located:
(i)
In damp or wet locations;
(ii)
Where exposed to gases, fumes, vapors, liquids, or other
agents having a deteriorating effect on the conductors or
equipment; or
(iii)
Where exposed to excessive temperatures.
(2)
Control equipment, utilization equipment, and busways approved
for use in dry locations only shall be protected against
damage from the weather during building construction.
(b)
Protection
against corrosion.
Metal raceways, cable armor, boxes, cable sheathing, cabinets,
elbows, couplings, fittings, supports, and support hardware
shall be of materials appropriate for the environment in which
they are to be installed.
§§1926.433-1926.440 [Reserved]
Safety
Requirements for Special Equipment
§1926.441 Batteries
and battery charging.
(a)
General
requirements—(1)
Batteries of the unsealed type shall be located in enclosures
with outside vents or in well ventilated rooms and shall be
arranged so as to prevent the escape of fumes, gases, or
electrolyte spray into other areas.
(2)
Ventilation shall be provided to ensure diffusion of the gases
from the battery and to prevent the accumulation of an
explosive mixture.
(3)
Racks and trays shall be substantial and shall be treated to
make them resistant to the electrolyte.
(4)
Floors shall be of acid resistant construction unless
protected from acid accumulations.
(5)
Face shields, aprons, and rubber gloves shall be provided for
workers handling acids or batteries.
(6)
Facilities for quick drenching of the eyes and body shall be
provided within 25 feet (7.62 m) of battery handling areas.
(7)
Facilities shall be provided for flushing and neutralizing
spilled electrolyte and for fire protection.
(b)
Charging—(1)
Battery charging installations shall be located in areas
designated for that purpose.
(2)
Charging apparatus shall be protected from damage by trucks.
(3)
When batteries are being charged, the vent caps shall be kept
in place to avoid electrolyte spray. Vent caps shall be
maintained in functioning condition.
§§1926.442-1926.448 [Reserved]
Definitions
§1926.449 Definitions
applicable to this subpart.
The
definitions given in this section apply to the terms used in
subpart K. The definitions given here for “approved”
and “qualified person” apply, instead of the
definitions given in §1926.32, to the use of these terms
in subpart K.
Acceptable.
An installation or equipment is acceptable to the Assistant
Secretary of Labor, and approved within the meaning of this
subpart K:
(a)
If it is accepted, or certified, or listed, or labeled, or
otherwise determined to be safe by a qualified testing
laboratory capable of determining the suitability of materials
and equipment for installation and use in accordance with this
standard; or
(b)
With respect to an installation or equipment of a kind which
no qualified 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 those provisions; or
(c)
With respect to custom-made equipment or related installations
which are designed, fabricated for, and intended for use by a
particular customer, if it is determined to be safe for its
intended use by its manufacturer on the basis of test data
which the employer keeps and makes available for inspection to
the Assistant Secretary and his authorized representatives.
Accepted.
An installation is “accepted” if it has been
inspected and found to be safe by a qualified testing
laboratory.
Accessible.
(As applied to wiring methods.) Capable of being removed or
exposed without damaging the building structure or finish, or
not permanently closed in by the structure or finish of the
building. (See “concealed”
and “exposed.”)
Accessible.
(As applied to equipment.) Admitting close approach; not
guarded by locked doors, elevation, or other effective means.
(See“Readily
accessible.”)
Ampacity.
The current in amperes 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, which is
installed or connecetcd 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.
Askarel.
A generic term for a group of nonflammable synthetic
chlorinated hydrocarbons used as electrical insulating media.
Askarels of various compositional types are used. Under arcing
conditions the gases produced, while consisting predominantly
of noncombustible hydrogen chloride, can include varying
amounts of combustible gases depending upon the askarel type.
Attachment
plug (Plug cap)(Cap).
A device which, by insertion in a receptacle, establishes
connection between the conductors of the attached flexible
cord and the conductors connected permanently to the
receptacle.
Automatic.
Self-acting, operating by its own mechanism when actuated by
some impersonal influence, as for example, a change in current
strength, pressure, temperature, or mechanical configuration.
Bare
conductor.
See “Conductor.”
Bonding.
The permanent joining of metallic parts to form an
electrically conductive path which will assure electrical
continuity and the capacity to conduct safely any current
likely to be imposed.
Bonding
jumper.
A reliable conductor to assure the required electrical
conductivity between metal parts required to be electrically
connected.
Branch
circuit.
The circuit conductors between the final overcurrent device
protecting the circuit and the outlet(s).
Building.
A structure which stands alone or which is cut off from
adjoining structures by fire walls with all openings therein
protected by approved fire doors.
Cabinet.
An enclosure designed either for surface or flush mounting,
and provided with a frame, mat, or trim in which a swinging
door or doors are or may be hung.
Certified.
Equipment is “certified” if it:
(a)
Has been tested and found by a qualified testing laboratory to
meet applicable test standards or to be safe for use in a
specified manner, and
(b)
Is of a kind whose production is periodically inspected by a
qualified testing laboratory. Certified equipment must bear a
label, tag, or other record of certification.
Circuit
breaker—(a)
(600 volts nominal, or less.) A device designed to open and
close a circuit by nonautomatic means and to open the circuit
automatically on a predetermined overcurrent without injury to
itself when properly applied within its rating.
(b)
(Over 600 volts, nominal.) A switching device capable of
making, carrying, and breaking currents under normal circuit
conditions, and also making, carrying for a specified time,
and breaking currents under specified abnormal circuit
conditions, such as those of short circuit.
Class
I locations.
Class I locations are those in which flammable gases or vapors
are or may be present in the air in quantities sufficient to
produce explosive or ignitible mixtures. Class I locations
include the following:
(a)
Class
I, Division 1.
A Class I, Division 1 location is a location:
(1)
In which ignitible concentrations of flammable gases or vapors
may exist under normal operating conditions; or
(2)
In which ignitible concentrations of such gases or vapors may
exist frequently because of repair or maintenance operations
or because of leakage; or
(3)
In which breakdown or faulty operation of equipment or
processes might release ignitible concentrations of flammable
gases or vapors, and might also cause simultaneous failure of
electric equipment.
Note:
This classification usually includes locations where volatile
flammable liquids or liquefied flammable gases are transferred
from one container to another; interiors of spray booths and
areas in the vicinity of spraying and painting operations
where volatile flammable solvents are used; locations
containing open tanks or vats of volatile flammable liquids;
drying rooms or compartments for the evaporation of flammable
solvents; inadequately ventilated pump rooms for flammable gas
or for volatile flammable liquids; and all other locations
where ignitible concentrations of flammable vapors or gases
are likely to occur in the course of normal operations.
(b)
Class
I, Division 2.
A Class I, Division 2 location is a location:
(1)
In which volatile flammable liquids or flammable gases are
handled, processed, or used, but in which the hazardous
liquids, vapors, or gases will normally be confined within
closed containers or closed systems from which they can escape
only in case of accidental rupture or breakdown of such
containers or systems, or in case of abnormal operation of
equipment; or
(2)
In which ignitible 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
(3)
That is adjacent to a Class I, Division 1 location, and to
which ignitible concentrations of gases or vapors might
occasionally be communicated unless such communication is
prevented by adequate positive-pressure ventilation from a
source of clean air, and effective safeguards against
ventilation failure are provided.
Note:
This classification usually includes locations where volatile
flammable liquids or flammable gases or vapors are used, but
which would become hazardous only in case of an accident or of
some unusual operating condition. The quantity of flammable
material that might escape in case of accident, the adequacy
of ventilating equipment, the total area involved, and the
record of the industry or business with respect to explosions
or fires are all factors that merit consideration in
determining the classification and extent of each location.
Piping
without valves, checks, meters, and similar devices would not
ordinarily introduce a hazardous condition even though used
for flammable liquids or gases. Locations used for the storage
of flammable liquids or of liquefied or compressed gases in
sealed containers would not normally be considered hazardous
unless also subject to other hazardous conditions.
Electrical
conduits and their associated enclosures separated from
process fluids by a single seal or barrier are classed as a
Division 2 location if the outside of the conduit and
enclosures is a nonhazardous location.
Class
II locations.
Class II locations are those that are hazardous because of the
presence of combustible dust. Class II locations include the
following:
(a)
Class
II, Division 1.
A Class II, Division 1 location is a location:
(1)
In which combustible dust is or may be in suspension in the
air under normal operating conditions, in quantities
sufficient to produce explosive or ignitible mixtures; or
(2)
Where mechanical failure or abnormal operation of machinery or
equipment might cause such explosive or ignitible mixtures to
be produced, and might also provide a source of ignition
through simultaneous failure of electric equipment, operation
of protection devices, or from other causes, or
(3)
In which combustible dusts of an electrically conductive
nature may be present.
Note:
Combustible dusts which are electrically nonconductive include
dusts produced in the handling and processing of grain and
grain products, pulverized sugar and cocoa, dried egg and milk
powders, pulverized spices, starch and pastes, potato and
woodflour, oil meal from beans and seed, dried hay, and other
organic materials which 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.
(b)
Class
II, Division 2.
A Class II, Division 2 location is a location in which:
(1)
Combustible dust will not normally be in suspension in the air
in quantities sufficient to produce explosive or ignitible
mixtures, and dust accumulations are normally insufficient to
interfere with the normal operation of electrical equipment or
other apparatus; or
(2)
Dust may be in suspension in the air as a result of infrequent
malfunctioning of handling or processing equipment, and dust
accumulations resulting therefrom may be ignitible by abnormal
operation or failure of electrical equipment or other
apparatus.
Note:
This classification includes locations where dangerous
concentrations of suspended dust would not be likely but where
dust accumulations might form on or in the vicinity of
electric equipment. These areas may contain equipment from
which appreciable quantities of dust would escape under
abnormal operating conditions or be adjacent to a Class II
Division 1 location, as described above, into which an
explosive or ignitible concentration of dust may be put into
suspension under abnormal operating conditions.
Class
III locations.
Class III locations are those that are hazardous because of
the presence of easily ignitible fibers or flyings but in
which such fibers or flyings are not likely to be in
suspension in the air in quantities sufficient to produce
ignitible mixtures. Class 111 locations include the following:
(a)
Class
III, Division 1.
A Class III, Division 1 location is a location in which easily
ignitible fibers or materials producing combustible flyings
are handled, manufactured, or used.
Note:
Easily ignitible fibers and flyings include rayon, cotton
(including cotton linters and cotton waste), sisal or
henequen, istle, jute, hemp, tow, cocoa fiber, oakum, baled
waste kapok, Spanish moss, excelsior, sawdust, woodchips, and
other material of similar nature.
(b)
Class
III, Division 2.
A Class III, Division 2 location is a location in which easily
ignitible fibers are stored or handled, except in process of
manufacture.
Collector
ring.
A collector ring is an assembly of slip rings for transferring
electrical energy from a stationary to a rotating member.
Concealed.
Rendered inaccessible by the structure or finish of the
building. Wires in concealed raceways are considered
concealed, even though they may become accessible by
withdrawing them. [See “Accessible.
(As applied to wiring methods.)”]
Conductor—(a)
Bare.
A conductor having no covering or electrical insulation
whatsoever.
(b)
Covered.
A conductor encased within material of composition or
thickness that is not recognized as electrical insulation.
(c)
Insulated.
A conductor encased within material of composition and
thickness that is recognized as electrical insulation.
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.
Device.
A unit of an electrical system which is intended to carry but
not utilize electric energy.
Disconnecting
means.
A device, or group of devices, or other means by which the
conductors of a circuit can be disconnected from their source
of supply.
Disconnecting
(or Isolating) switch.
(Over 600 volts, nominal.) A mechanical switching device used
for isolating a circuit or equipment from a source of power.
Dry
location.
See “Location.”
Enclosed.
Surrounded by a case, housing, fence or walls which will
prevent persons from accidentally contacting energized parts.
Enclosure.
The case or housing of apparatus, or the fence or walls
surrounding an installation to prevent personnel from
accidentally contacting energized parts, or to protect the
equipment from physical damage.
Equipment.
A general term including material, fittings, devices,
appliances, fixtures, apparatus, and the like, used as a part
of, or in connection with, an electrical installation.
Equipment
grounding conductor.
See “Grounding
conductor, equipment.”
Explosion-proof
apparatus.
Apparatus enclosed in a case that is capable of withstanding
an explosion of a specified gas or vapor which may occur
within it and of preventing the ignition of a specified gas or
vapor surrounding the enclosure by sparks, flashes, or
explosion of the gas or vapor within, and which operates at
such an external temperature that it will not ignite a
surrounding flammable atmosphere.
Exposed.
(As applied to live parts.) Capable of being inadvertently
touched or approached nearer than a safe distance by a person.
It is applied to parts not suitably guarded, isolated, or
insulated. (See “Accessible
and “Concealed.”)
Exposed.
(As applied to wiring methods.) On or attached to the surface
or behind panels designed to allow access. [See “Accessible.
(As applied to wiring methods.)”]
Exposed.
(For the purposes of §1926.408(d), Communications
systems.) Where the circuit is in such a position that in case
of failure of supports or insulation, contact with another
circuit may result.
Externally
operable.
Capable of being operated without exposing the operator to
contact with live parts.
Feeder.
All circuit conductors between the service equipment, or the
generator switchboard of an isolated plant, and the final
branch-circuit overcurrent device.
Festoon
lighting.
A string of outdoor lights suspended between two points more
than 15 feet (4.57 m) apart.
Fitting.
An accessory such as a locknut, bushing, or other part of a
wiring system that is intended primarily to perform a
mechanical rather than an electrical function.
Fuse.
(Over 600 volts, nominal.) An overcurrent protective device
with a circuit opening fusible part that is heated and severed
by the passage of overcurrent through it. A fuse comprises all
the parts that form a unit capable of performing the
prescribed functions. It may or may not be the complete device
necessary to connect it into an electrical circuit.
Ground.
A conducting connection, whether intentional or accidental,
between an electrical circuit or equipment and the earth, or
to some conducting body that serves in place of the earth.
Grounded.
Connected to earth or to some conducting body that serves in
place of the earth.
Grounded,
effectively
(Over 600 volts, nominal.) Permanently connected to earth
through a ground connection of sufficiently low impedance and
having sufficient ampacity that ground fault current which may
occur cannot build up to voltages dangerous to personnel.
Grounded
conductor.
A system or circuit conductor that is intentionally grounded.
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 and/or the grounding electrode
conductor at the service equipment or at the source of a
separately derived system.
Grounding
electrode conductor.
The conductor used to connect the grounding electrode to the
equipment grounding conductor and/or to the grounded conductor
of the circuit at the service equipment or at the source of a
separately derived system.
Ground-fault
circuit interrupter.
A device for the protection of personnel that functions to
deenergize a circuit or portion thereof 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.
Hoistway.
Any shaftway, hatchway, well hole, or other vertical opening
or space in which an elevator or dumbwaiter is designed to
operate.
Identified
(conductors or terminals).
Identified, as used in reference to a conductor or its
terminal, means that such conductor or terminal can be
recognized as grounded.
Identified
(for the use).
Recognized as suitable for the specific purpose, function,
use, environment, application, etc. where described as a
requirement in this standard. Suitability of equipment for a
specific purpose, environment, or application is determined by
a qualified testing laboratory where such identification
includes labeling or listing.
Insulated
conductor.
See “Conductor.”
Interrupter
switch.
(Over 600 volts, nominal.) A switch capable of making,
carrying, and interrupting specified currents.
Intrinsically
safe equipment and associated wiring.
Equipment and associated wiring in which any spark or thermal
effect, produced either normally or in specified fault
conditions, is incapable, under certain prescribed test
conditions, of causing ignition of a mixture of flammable or
combustible material in air in its most easily ignitible
concentration.
Isolated.
Not readily accessible to persons unless special means for
access are used.
Isolated
power system.
A system comprising an isolating transformer or its
equivalent, a line isolation monitor, and its ungrounded
circuit conductors.
Labeled.
Equipment or materials to which has been attached a label,
symbol or other identifying mark of a qualified testing
laboratory which indicates compliance with appropriate
standards or performance 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.
Listed.
Equipment or materials included in a list published by a
qualified testing laboratory whose listing states either that
the equipment or material meets appropriate standards or has
been tested and found suitable for use in a specified manner.
Location—(a)
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.
(b)
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.
(c)
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 locations
exposed to weather and unprotected.
Mobile
X-ray.
X-ray equipment mounted on a permanent base with wheels and/or
casters 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.
Outlet.
A point on the wiring system at which current is taken to
supply utilization equipment.
Overcurrent.
Any current in excess of the rated current of equipment or the
ampacity of a conductor. It may result from overload (see
definition), short circuit, or ground fault. A current in
excess of rating may be accommodated by certain equipment and
conductors for a given set of conditions. Hence the rules for
overcurrent protection are specific for particular situations.
Overload.
Operation of equipment in excess of normal, full load rating,
or of a conductor in excess of rated ampacity which, when it
persists for a sufficient length of time, would cause damage
or dangerous overheating. A fault, such as a short circuit or
ground fault, is not an overload. (See“Overcurrent.”)
Panelboard.
A single panel or group of panel units designed for assembly
in the form of a single panel; including buses, automatic
overcurrent devices, and with or without switches for the
control of light, heat, or power circuits; designed to be
placed in a cabinet or cutout box placed in or against a wall
or partition and accessible only from the front. (See
“Switchboard.”)
Portable
X-ray.
X-ray equipment designed to be hand-carried.
Power
fuse.
(Over 600 volts, nominal.) See “Fuse.”
Power
outlet.
An enclosed assembly which may include receptacles, circuit
breakers, fuseholders, fused switches, buses and watt-hour
meter mounting means; intended to serve as a means for
distributing power required to operate mobile or temporarily
installed equipment.
Premises
wiring system.
That interior and exterior wiring, including power, lighting,
control, and signal circuit wiring together with all of its
associated hardware, fittings, and wiring devices, both
permanently and temporarily installed, which extends from the
load end of the service drop, or load end of the service
lateral conductors to the outlet(s). Such wiring does not
include wiring internal to appliances, fixtures, motors,
controllers, motor control centers, and similar equipment.
Qualified
person.
One familiar with the construction and operation of the
equipment and the hazards involved.
Qualified
testing laboratory.
A properly equipped and staffed testing laboratory which has
capabilities for and which provides the following services:
(a)
Experimental testing for safety of specified items of
equipment and materials referred to in this standard to
determine compliance with appropriate test standards or
performance in a specified manner;
(b)
Inspecting the run of such items of equipment and materials at
factories for product evaluation to assure compliance with the
test standards;
(c)
Service-value determinations through field inspections to
monitor the proper use of labels on products and with
authority for recall of the label in the event a hazardous
product is installed;
(d)
Employing a controlled procedure for identifying the listed
and/or labeled equipment or materials tested; and
(e)
Rendering creditable reports or findings that are objective
and without bias of the tests and test methods employed.
Raceway.
A channel designed expressly for holding wires, cables, or
busbars, with additional functions as permitted in this
subpart. Raceways may be of metal or insulating material, and
the term includes rigid metal conduit, rigid nonmetallic
conduit, intermediate metal conduit, liquidtight flexible
metal conduit, flexible metallic tubing, flexible metal
conduit, electrical metallic tubing, underfloor raceways,
cellular concrete floor raceways, cellular metal floor
raceways, surface raceways, wireways, and busways.
Readily
accessible.
Capable of being reached quickly for operation, renewal, or
inspections, without requiring those to whom ready access is
requisite to climb over or remove obstacles or to resort to
portable ladders, chairs, etc. (See “Accessible.”)
Receptacle.
A receptacle is a contact device installed at the outlet for
the connection of a single attachment plug. A single
receptacle is a single contact device with no other contact
device on the same yoke. A multiple receptacle is a single
device containing two or more receptacles.
Receptacle
outlet.
An outlet where one or more receptacles are installed.
Remote-control
circuit.
Any electric circuit that controls any other circuit through a
relay or an equivalent device.
Sealable
equipment.
Equipment enclosed in a case or cabinet that is provided with
a means of sealing or locking so that live parts cannot be
made accessible without opening the enclosure. The equipment
may or may not be operable without opening the enclosure.
Separately
derived system.
A premises wiring system whose power is derived from
generator, transformer, or converter windings and has no
direct electrical connection, including a solidly connected
grounded circuit conductor, to supply conductors originating
in another system.
Service.
The conductors and equipment for delivering energy from the
electricity supply system to the wiring system of the premises
served.
Service
conductors.
The supply conductors that extend from the street main or from
transformers to the service equipment of the premises
supplied.
Service
drop.
The overhead service conductors from the last pole or other
aerial support to and including the splices, if any,
connecting to the service-entrance conductors at the building
or other structure.
Service-entrance
conductors, overhead system.
The service conductors between the terminals of the service
equipment and a point usually outside the building, clear of
building walls, where joined by tap or splice to the service
drop.
Service-entrance
conductors, underground system.
The service conductors between the terminals of the service
equipment and the point of connection to the service lateral.
Where service equipment is located outside the building walls,
there may be no service-entrance conductors, or they may be
entirely outside the building.
Service
equipment.
The necessary equipment, usually consisting of a circuit
breaker or switch and fuses, and their accessories, located
near the point of entrance of supply conductors to a building
or other structure, or an otherwise defined area, and intended
to constitute the main control and means of cutoff of the
supply.
Service
raceway.
The raceway that encloses the service-entrance conductors.
Signaling
circuit.
Any electric circuit that energizes signaling equipment.
Switchboard.
A large single panel, frame, or assembly of panels which have
switches, buses, instruments, overcurrent and other protective
devices mounted on the face or back or both. Switchboards are
generally accessible from the rear as well as from the front
and are not intended to be installed in cabinets. (See
“Panelboard.”)
Switches—(a)
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.
(b)
General-use
snap switch.
A form of general-use switch so constructed that it can be
installed in flush device boxes or on outlet box covers, or
otherwise used in conjunction with wiring systems recognized
by this subpart.
(c)
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.
(d)
Motor-circuit
switch.
A switch, rated in horsepower, capable of interrupting the
maximum operating overload current of a motor of the same
horsepower rating as the switch at the rated voltage.
Switching
devices.
(Over 600 volts, nominal.) Devices designed to close and/or
open one or more electric circuits. Included in this category
are circuit breakers, cutouts, disconnecting (or isolating)
switches, disconnecting means, and interrupter switches.
Transportable
X-ray.
X-ray equipment installed in a vehicle or that may readily be
disassembled for transport in a vehicle.
Utilization
equipment.
Utilization equipment means equipment which utilizes electric
energy for mechanical, chemical, heating, lighting, or similar
useful purpose.
Utilization
system.
A utilization system is a system which provides electric power
and light for employee workplaces, and includes the premises
wiring system and utilization equipment.
Ventilated.
Provided with a means to permit circulation of air sufficient
to remove an excess of heat, fumes, or vapors.
Volatile
flammable liquid.
A flammable liquid having a flash point below 38 degrees C
(100 degrees F) or whose temperature is above its flash point,
or a Class II combustible liquid having a vapor pressure not
exceeding 40 psia (276 kPa) at 38 °C (100 °F) whose
temperature is above its flash point.
Voltage.
(Of a circuit.) The greatest root-mean-square (effective)
difference of potential between any two conductors of the
circuit concerned.
Voltage,
nominal.
A nominal value assigned to a circuit or system for the
purpose of conveniently designating its voltage class (as
120/240, 480Y/277, 600, etc.). The actual voltage at which a
circuit operates can vary from the nominal within a range that
permits satisfactory operation of equipment.
Voltage
to ground.
For grounded circuits, the voltage between the given conductor
and that point or conductor of the circuit that is grounded;
for ungrounded circuits, the greatest voltage between the
given conductor and any other conductor of the circuit.
Watertight.
So constructed that moisture will not enter the enclosure.
Weatherproof.
So constructed or protected that exposure to the weather will
not interfere with successful operation. Rainproof, raintight,
or watertight equipment can fulfill the requirements for
weatherproof where varying weather conditions other than
wetness, such as snow, ice, dust, or temperature extremes, are
not a factor.
Wet
location.
See “Location.”
|