(ii) Working space required by this standard may not be used for
storage. When normally enclosed live parts are exposed for inspection
or servicing, the working space, if in a passageway or general open
space, shall be suitably guarded.
    (iii) At least one entrance of sufficient area shall be provided to
give access to the working space about electric equipment.
    (iv) For equipment rated 1200 amperes or more and over 1.83 m (6.0
ft) wide, containing overcurrent devices, switching devices, or control
devices, there shall be one entrance not less than 610 mm (24 in.) wide
and 1.98 m (6.5 ft) high at each end of the working space, except that:
    (A) Where the location permits a continuous and unobstructed way of
exit travel, one means of exit is permitted; or
    (B) Where the working space required by paragraph (g)(1)(i) of this
section is doubled, only one entrance to the working space is required;
however, the entrance shall be located so that the edge of the entrance
nearest the equipment is the minimum clear distance given in Table S-1
away from such equipment.
    (v) Illumination shall be provided for all working spaces about
service equipment, switchboards, panelboards, and motor control centers
installed indoors. Additional lighting fixtures are not required where
the working space is illuminated by an adjacent light source. In
electric equipment rooms, the illumination may not be controlled by
automatic means only.
    (vi) The minimum headroom of working spaces about service
equipment, switchboards, panelboards, or motor control centers shall be
as follows:
    (A) For installations built before August 13, 2007, 1.91 m (6.25
ft); and
    (B) For installations built on or after August 13, 2007, 1.98 m
(6.5 ft), except that where the electrical equipment exceeds 1.98 m
(6.5 ft) in height, the minimum headroom may not be less than the
height of the equipment.

              Table S-1.--Minimum Depth of Clear Working Space at Electric Equipment, 600 V or Less
----------------------------------------------------------------------------------------------------------------
                                                          Minimum clear distance for condition \2\ \3\
                                               -----------------------------------------------------------------
           Nominal voltage to ground                 Condition A           Condition B           Condition C
                                               -----------------------------------------------------------------
                                                    m          ft         m          ft         m          ft
----------------------------------------------------------------------------------------------------------------
0-150.........................................     \1\0.9     \1\3.0     \1\0.9     \1\3.0        0.9        3.0
151-600.......................................     \1\0.9     \1\3.0        1.0        3.5        1.2       4.0
----------------------------------------------------------------------------------------------------------------
 Notes to Table S-1:
 1. Minimum clear distances may be 0.7 m (2.5 ft) for installations built before April 16, 1981.
 2. Conditions A, B, and C are as follows:
 Condition A--Exposed live parts on one side and no live or grounded parts on the other side of the working
  space, or exposed live parts on both sides effectively guarded by suitable wood or other insulating material.
  Insulated wire or insulated busbars operating at not over 300 volts are not considered live parts.
 Condition B--Exposed live parts on one side and grounded parts on the other side.
 Condition C--Exposed live parts on both sides of the work space (not guarded as provided in Condition A) with
  the operator between.
 3. Working space is not required in back of assemblies such as dead-front switchboards or motor control centers
  where there are no renewable or adjustable parts (such as fuses or switches) on the back and where all
  connections are accessible from locations other than the back. Where rear access is required to work on
  deenergized parts on the back of enclosed equipment, a minimum working space of 762 mm (30 in.) horizontally
  shall be provided.

    (vii) Switchboards, panelboards, and distribution boards installed
for the control of light and power circuits, and motor control centers
shall be located in dedicated spaces and protected from damage.
    (A) For indoor installation, the dedicated space shall comply with
the following:
    (1) The space equal to the width and depth of the equipment and
extending from the floor to a height of 1.83 m (6.0 ft) above the
equipment or to the structural ceiling, whichever is lower, shall be
dedicated to the electrical installation. Unless isolated from
equipment by height or physical enclosures or covers that will afford
adequate mechanical protection from vehicular traffic or accidental
contact by unauthorized personnel or that complies with paragraph
(g)(1)(vii)(A)(2) of this section, piping, ducts, or equipment foreign
to the electrical installation may not be located in this area;
    (2) The space equal to the width and depth of the equipment shall
be kept clear of foreign systems unless protection is provided to avoid
damage from condensation, leaks, or breaks in such foreign systems.
This area shall extend from the top of the electric equipment to the
structural ceiling;
    (3) Sprinkler protection is permitted for the dedicated space where
the piping complies with this section; and
    (4) Control equipment that by its very nature or because of other
requirements in this subpart must be adjacent to or within sight of its
operating machinery is permitted in the dedicated space.

    Note to paragraph (g)(1)(vii)(A) of this section: A dropped,
suspended, or similar ceiling that does not add strength to the
building structure is not considered a structural ceiling.

    (B) Outdoor electric equipment shall be installed in suitable
enclosures and shall be protected from accidental contact by
unauthorized personnel, or by vehicular traffic, or by accidental
spillage or leakage from piping systems. No architectural appurtenance
or other equipment may be located in the working space required by
paragraph (g)(1)(i) of this section.
    (2) Guarding of live parts. (i) Except as elsewhere required or
permitted by this standard, live parts of electric equipment operating
at 50 volts or more shall be guarded against accidental

contact by use of approved cabinets or other forms of approved
enclosures or by any of the following means:
    (A) By location in a room, vault, or similar enclosure that is
accessible only to qualified persons;
    (B) By suitable permanent, substantial partitions or screens so
arranged so that only qualified persons will have access to the space
within reach of the live parts. Any openings in such partitions or
screens shall be so sized and located that persons are not likely to
come into accidental contact with the live parts or to bring conducting
objects into contact with them;
    (C) By placement on a suitable balcony, gallery, or platform so
elevated and otherwise located as to prevent access by unqualified
persons; or
    (D) By elevation of 2.44 m (8.0 ft) or more above the floor or
other working surface.
    (ii) In locations where electric equipment is likely to be exposed
to physical damage, enclosures or guards shall be so arranged and of
such strength as to prevent such damage.
    (iii) Entrances to rooms and other guarded locations containing
exposed live parts shall be marked with conspicuous warning signs
forbidding unqualified persons to enter.
    (h) Over 600 volts, nominal--(1) General. Conductors and equipment
used on circuits exceeding 600 volts, nominal, shall comply with all
applicable provisions of the paragraphs (a) through (g) of this section
and with the following provisions, which supplement or modify the
preceding requirements. However, paragraphs (h)(2), (h)(3), and (h)(4)
of this section do not apply to the equipment on the supply side of the
service point.
    (2) Enclosure for electrical installations. (i) Electrical
installations in a vault, room, or closet or in an area surrounded by a
wall, screen, or fence, access to which is controlled by lock and key
or other approved means, are considered to be accessible to qualified
persons only. The type of enclosure used in a given case shall be
designed and constructed according to the hazards associated with the
installation.
    (ii) For installations other than equipment described in paragraph
(h)(2)(v) of this section, a wall, screen, or fence shall be used to
enclose an outdoor electrical installation to deter access by persons
who are not qualified. A fence may not be less than 2.13 m (7.0 ft) in
height or a combination of 1.80 m (6.0 ft) or more of fence fabric and
a 305-mm (1-ft) or more extension utilizing three or more strands of
barbed wire or equivalent.
    (iii) The following requirements apply to indoor installations that
are accessible to other than qualified persons:
    (A) The installations shall be made with metal-enclosed equipment
or shall be enclosed in a vault or in an area to which access is
controlled by a lock;
    (B) Metal-enclosed switchgear, unit substations, transformers, pull
boxes, connection boxes, and other similar associated equipment shall
be marked with appropriate caution signs; and
    (C) Openings in ventilated dry-type transformers and similar
openings in other equipment shall be designed so that foreign objects
inserted through these openings will be deflected from energized parts.
    (iv) Outdoor electrical installations having exposed live parts
shall be accessible to qualified persons only.
    (v) The following requirements apply to outdoor enclosed equipment
accessible to unqualified employees:
    (A) Ventilating or similar openings in equipment shall be so
designed that foreign objects inserted through these openings will be
deflected from energized parts;
    (B) Where exposed to physical damage from vehicular traffic,
suitable guards shall be provided;
    (C) Nonmetallic or metal-enclosed equipment located outdoors and
accessible to the general public shall be designed so that exposed nuts
or bolts cannot be readily removed, permitting access to live parts;
    (D) Where nonmetallic or metal-enclosed equipment is accessible to
the general public and the bottom of the enclosure is less than 2.44 m
(8.0 ft) above the floor or grade level, the enclosure door or hinged
cover shall be kept locked; and
    (E) Except for underground box covers that weigh over 45.4 kg (100
lb), doors and covers of enclosures used solely as pull boxes, splice
boxes, or junction boxes shall be locked, bolted, or screwed on.
    (3) Work space about equipment. Sufficient space shall be provided
and maintained about electric equipment to permit ready and safe
operation and maintenance of such equipment. Where energized parts are
exposed, the minimum clear work space may not be less than 1.98 m (6.5
ft) high (measured vertically from the floor or platform) or less than
914 mm (3.0 ft) wide (measured parallel to the equipment). The depth
shall be as required in paragraph (h)(5)(i) of this section. In all
cases, the work space shall be adequate to permit at least a 90-degree
opening of doors or hinged panels.
    (4) Entrance and access to work space. (i) At least one entrance
not less than 610 mm (24 in.) wide and 1.98 m (6.5 ft) high shall be
provided to give access to the working space about electric equipment.
    (A) On switchboard and control panels exceeding 1.83 m (6.0 ft) in
width, there shall be one entrance at each end of such boards unless
the location of the switchboards and control panels permits a
continuous and unobstructed way of exit travel, or unless the work
space required in paragraph (h)(5)(i) of this section is doubled.
    (B) Where one entrance to the working space is permitted under the
conditions described in paragraph (h)(4)(i)(A) of this section, the
entrance shall be located so that the edge of the entrance nearest the
switchboards and control panels is at least the minimum clear distance
given in Table S-2 away from such equipment.
    (C) Where bare energized parts at any voltage or insulated
energized parts above 600 volts, nominal, to ground are located
adjacent to such entrance, they shall be suitably guarded.
    (ii) Permanent ladders or stairways shall be provided to give safe
access to the working space around electric equipment installed on
platforms, balconies, mezzanine floors, or in attic or roof rooms or
spaces.
    (5) Working space and guarding. (i)(vi) Except as elsewhere
required or permitted in this subpart, the minimum clear working space
in the direction of access to live parts of electric equipment may not
be less than specified in Table S-2. Distances shall be measured from
the live parts, if they are exposed, or from the enclosure front or
opening, if they are enclosed.
    (ii) If switches, cutouts, or other equipment operating at 600
volts, nominal, or less, are installed in a room or enclosure where
there are exposed live parts or exposed wiring operating at over 600
volts, nominal, the high-voltage equipment shall be effectively
separated from the space occupied by the low-voltage equipment by a
suitable partition, fence, or screen. However, switches or other
equipment operating at 600 volts, nominal, or less, and serving only
equipment within the high-voltage vault, room, or enclosure may be
installed in the high-voltage enclosure, room, or vault if accessible
to qualified persons only.
    (iii) The following requirements apply to the entrances to all
buildings, rooms, or enclosures containing exposed live parts or
exposed conductors operating at over 600 volts, nominal:

    (A) The entrances shall be kept locked unless they are under the
observation of a qualified person at all times; and
    (B) Permanent and conspicuous warning signs shall be provided,
reading substantially as follows:
``DANGER--HIGH VOLTAGE--KEEP OUT.''
    (iv) Illumination shall be provided for all working spaces about
electric equipment.
    (A) The lighting outlets shall be arranged so that persons changing
lamps or making repairs on the lighting system will not be endangered
by live parts or other equipment.
    (B) The points of control shall be located so that persons are
prevented from contacting any live part or moving part of the equipment
while turning on the lights.
    (v) Unguarded live parts above working space shall be maintained at
elevations not less than specified in Table S-3.
    (vi) Pipes or ducts that are foreign to the electrical installation
and that require periodic maintenance or whose malfunction would
endanger the operation of the electrical system may not be located in
the vicinity of service equipment, metal-enclosed power switchgear, or
industrial control assemblies. Protection shall be provided where
necessary to avoid damage from condensation leaks and breaks in such
foreign systems.

    Note to paragraph (h)(5)(vi) of this section: Piping and other
facilities are not considered foreign if provided for fire
protection of the electrical installation.

               Table S-2.--Minimum Depth of Clear Working Space at Electric Equipment, Over 600 V
----------------------------------------------------------------------------------------------------------------
                                                          Minimum clear distance for condition \2\ \3\
                                               -----------------------------------------------------------------
           Nominal voltage to ground                 Condition A           Condition B           Condition C
                                               -----------------------------------------------------------------
                                                    m          ft         m          ft         m          ft
----------------------------------------------------------------------------------------------------------------
601-2500 V....................................        0.9        3.0        1.2        4.0        1.5        5.0
2501-9000 V...................................        1.2        4.0        1.5        5.0        1.8        6.0
9001 V-25 kV..................................        1.5        5.0        1.8        6.0        2.8        9.0
Over 25-75 kV \1\.............................        1.8        6.0        2.5        8.0        3.0       10.0
Above 75 kV \1\...............................        2.5        8.0        3.0       10.0        3.7      12.0
----------------------------------------------------------------------------------------------------------------
Notes to Table S-2:
\1\ Minimum depth of clear working space in front of electric equipment with a nominal voltage to ground above
  25,000 volts may be the same as that for 25,000 volts under Conditions A, B, and C for installations built
  before April 16, 1981.
\2\ Conditions A, B, and C are as follows:
Condition A--Exposed live parts on one side and no live or grounded parts on the other side of the working
  space, or exposed live parts on both sides effectively guarded by suitable wood or other insulating material.
  Insulated wire or insulated busbars operating at not over 300 volts are not considered live parts.
Condition B--Exposed live parts on one side and grounded parts on the other side. Concrete, brick, and tile
  walls are considered as grounded surfaces.
Condition C--Exposed live parts on both sides of the work space (not guarded as provided in Condition A) with
  the operator between.
\3\ Working space is not required in back of equipment such as dead-front switchboards or control assemblies
  that has no renewable or adjustable parts (such as fuses or switches) on the back and where all connections
  are accessible from locations other than the back. Where rear access is required to work on the deenergized
  parts on the back of enclosed equipment, a minimum working space 762 mm (30 in.) horizontally shall be
  provided.

    Table S-3.--Elevation of Unguarded Live Parts Above Working Space
------------------------------------------------------------------------
                                                 Elevation
 Nominal voltage between phases  ---------------------------------------
                                           m                  ft
------------------------------------------------------------------------
601-7500 V......................  \1\ 2.81..........  \1\ 9.01.
7501 V-35 kV....................  2.8...............  9.0.
Over 35 kV......................  2.8 + 9.5 mm/kV     9.0 + 0.37 in./kV
                                   over 35 kV.         over 35 kV.
------------------------------------------------------------------------
\1\ The minimum elevation may be 2.6 m (8.5 ft) for installations built
  before August 13, 2007. The minimum elevation may be 2.4 m (8.0 ft)
  for installations built before April 16, 1981, if the nominal voltage
  between phases is in the range of 601-6600 volts.

Sec.  1910.304  Wiring design and protection.

    (a) Use and identification of grounded and grounding conductors--
(1) Identification of conductors. (i) A conductor used as a grounded
conductor shall be identifiable and distinguishable from all other
conductors.
    (ii) A conductor used as an equipment grounding conductor shall be
identifiable and distinguishable from all other conductors.
    (2) Polarity of connections. No grounded conductor may be attached
to any terminal or lead so as to reverse designated polarity.
    (3) Use of grounding terminals and devices. A grounding terminal or
grounding-type device on a receptacle, cord connector, or attachment
plug may not be used for purposes other than grounding.
    (b) Branch circuits--(1) Identification of multiwire branch
circuits. Where more than one nominal voltage system exists in a
building containing multiwire branch circuits, each ungrounded
conductor of a multiwire branch circuit, where accessible, shall be
identified by phase and system. The means of identification shall be
permanently posted at each branch-circuit panelboard.
    (2) Receptacles and cord connectors. (i) Receptacles installed on
15- and 20-ampere branch circuits shall be of the grounding type except
as permitted for replacement receptacles in paragraph (b)(2)(iv) of
this section. Grounding-type receptacles shall be installed only on
circuits of the voltage class and current for which they are rated,
except as provided in Table S-4 and Table S-5.
    (ii) Receptacles and cord connectors having grounding contacts
shall have those contacts effectively grounded except for receptacles
mounted on portable and vehicle-mounted generators in accordance with
paragraph (g)(3) of this section and replacement

receptacles installed in accordance with paragraph (b)(2)(iv) of this
section.
    (iii) The grounding contacts of receptacles and cord connectors
shall be grounded by connection to the equipment grounding conductor of
the circuit supplying the receptacle or cord connector. The branch
circuit wiring method shall include or provide an equipment grounding
conductor to which the grounding contacts of the receptacle or cord
connector shall be connected.
    (iv) Replacement of receptacles shall comply with the following
requirements:
    (A) Where a grounding means exists in the receptacle enclosure or a
grounding conductor is installed, grounding-type receptacles shall be
used and shall be connected to the grounding means or conductor;
    (B) Ground-fault circuit-interrupter protected receptacles shall be
provided where replacements are made at receptacle outlets that are
required to be so protected elsewhere in this subpart; and
    (C) Where a grounding means does not exist in the receptacle
enclosure, the installation shall comply with one of the following
provisions:
    (1) A nongrounding-type receptacle may be replaced with another
nongrounding-type receptacle; or
    (2) A nongrounding-type receptacle may be replaced with a ground-
fault circuit-interrupter-type of receptacle that is marked ``No
Equipment Ground;'' an equipment grounding conductor may not be
connected from the ground-fault circuit-interrupter-type receptacle to
any outlet supplied from the ground-fault circuit-interrupter
receptacle; or
    (3) A nongrounding-type receptacle may be replaced with a
grounding-type receptacle where supplied through a ground-fault
circuit-interrupter; the replacement receptacle shall be marked ``GFCI
Protected'' and ``No Equipment Ground;'' an equipment grounding
conductor may not be connected to such grounding-type receptacles.
    (v) Receptacles connected to circuits having different voltages,
frequencies, or types of current (ac or dc) on the same premises shall
be of such design that the attachment plugs used on these circuits are
not interchangeable.
    (3) Ground-fault circuit interrupter protection for personnel. (i)
All 125-volt, single-phase, 15- and 20-ampere receptacles installed in
bathrooms or on rooftops shall have ground-fault circuit-interrupter
protection for personnel.
    (ii) The following requirements apply to temporary wiring
installations that are used during maintenance, remodeling, or repair
of buildings, structures, or equipment or during similar construction-
like activities.
    (A) All 125-volt, single-phase, 15-, 20-, and 30-ampere receptacle
outlets that are not part of the permanent wiring of the building or
structure and that are in use by personnel shall have ground-fault
circuit-interrupter protection for personnel.

    Note 1 to paragraph (b)(3)(ii)(A) of this section: A cord
connector on an extension cord set is considered to be a receptacle
outlet if the cord set is used for temporary electric power.

    Note 2 to paragraph (b)(3)(ii)(A) of this section: Cord sets and
devices incorporating the required ground-fault circuit-interrupter
that are connected to the receptacle closest to the source of power
are acceptable forms of protection.

    (B) Receptacles other than 125 volt, single-phase, 15-, 20-, and
30-ampere receptacles that are not part of the permanent wiring of the
building or structure and that are in use by personnel shall have
ground-fault circuit-interrupter protection for personnel.
    (C) Where the ground-fault circuit-interrupter protection required
by paragraph (b)(3)(ii)(B) of this section is not available for
receptacles other than 125-volt, single-phase, 15-, 20-, and 30-ampere,
the employer shall establish and implement an assured equipment
grounding conductor program covering cord sets, receptacles that are
not a part of the building or structure, and equipment connected by
cord and plug that are available for use or used by employees on those
receptacles. This program shall comply with the following requirements:
    (1) A written description of the program, including the specific
procedures adopted by the employer, shall be available at the jobsite
for inspection and copying by the Assistant Secretary of Labor and any
affected employee;
    (2) The employer shall designate one or more competent persons to
implement the program;
    (3) Each cord set, attachment cap, plug, and receptacle of cord
sets, and any equipment connected by cord and plug, except cord sets
and receptacles which are fixed and not exposed to damage, shall be
visually inspected before each day's use for external defects, such as
deformed or missing pins or insulation damage, and for indications of
possible internal damage. Equipment found damaged or defective shall
not be used until repaired;
    (4) The following tests shall be performed on all cord sets and
receptacles which are not a part of the permanent wiring of the
building or structure, and cord- and plug-connected equipment required
to be grounded:
    (i) All equipment grounding conductors shall be tested for
continuity and shall be electrically continuous;
    (ii) Each receptacle and attachment cap or plug shall be tested for
correct attachment of the equipment grounding conductor. The equipment
grounding conductor shall be connected to its proper terminal; and
    (iii) All required tests shall be performed before first use;
before equipment is returned to service following any repairs; before
equipment is used after any incident which can be reasonably suspected
to have caused damage (for example, when a cord set is run over); and
at intervals not to exceed 3 months, except that cord sets and
receptacles which are fixed and not exposed to damage shall be tested
at intervals not exceeding 6 months;
    (5) The employer shall not make available or permit the use by
employees of any equipment which has not met the requirements of
paragraph (b)(3)(ii)(C) of this section; and
    (6) Tests performed as required in paragraph (b)(3)(ii)(C) of this
section shall be recorded. This test record shall identify each
receptacle, cord set, and cord- and plug-connected equipment that
passed the test and shall indicate the last date it was tested or the
interval for which it was tested. This record shall be kept by means of
logs, color coding, or other effective means and shall be maintained
until replaced by a more current record. The record shall be made
available on the jobsite for inspection by the Assistant Secretary and
any affected employee.
    (4) Outlet devices. Outlet devices shall have an ampere rating not
less than the load to be served and shall comply with the following
provisions:
    (i) Where connected to a branch circuit having a rating in excess
of 20 amperes, lampholders shall be of the heavy-duty type. A heavy-
duty lampholder shall have a rating of not less than 660 watts if of
the admedium type and not less than 750 watts if of any other type; and
    (ii) Receptacle outlets shall comply with the following provisions:
    (A) A single receptacle installed on an individual branch circuit
shall have an ampere rating of not less than that of the branch
circuit;
    (B) Where connected to a branch circuit supplying two or more
receptacles or outlets, a receptacle may not supply a total cord- and
plug-connected load in excess of the maximum specified in Table S-4;
and

    (C) Where connected to a branch circuit supplying two or more
receptacles or outlets, receptacle ratings shall conform to the values
listed in Table S-5; or, where larger than 50 amperes, the receptacle
rating may not be less than the branch-circuit rating. However,
receptacles of cord- and plug-connected arc welders may have ampere
ratings not less than the minimum branch-circuit conductor ampacity.
    (5) Cord connections. A receptacle outlet shall be installed
wherever flexible cords with attachment plugs are used. Where flexible
cords are permitted to be permanently connected, receptacles may be
omitted.

     Table S-4.--Maximum Cord- and Plug-Connected Load to Receptacle
------------------------------------------------------------------------
                                                 Receptacle    Maximum
           Circuit rating  (amperes)               rating        load
                                                 (amperes)    (amperes)
------------------------------------------------------------------------
15 or 20......................................           15           12
20............................................           20           16
30............................................           30           24
------------------------------------------------------------------------

        Table S-5.--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, 600 volts, nominal, or less. The following
requirements apply to branch-circuit, feeder, and service conductors
rated 600 volts, nominal, or less and run outdoors as open conductors.
    (1) Conductors on poles. Conductors on poles shall have a
separation of not less than 305 mm (1.0 ft) where not placed on racks
or brackets. Conductors supported on poles shall provide a horizontal
climbing space not less than the following:
    (i) Power conductors below communication conductors--762 mm (30
in.);
    (ii) Power conductors alone or above communication conductors:
    (A) 300 volts or less--610 mm (24 in.),
    (B) Over 300 volts--762 mm (30 in.);
    (iii) Communication conductors below power conductors--same as
power conductors; and
    (iv) Communications conductors alone--no requirement.
    (2) Clearance from ground. Open conductors, open multiconductor
cables, and service-drop conductors of not over 600 volts, nominal,
shall conform to the minimum clearances specified in Table S-6.

                                       Table S-66.--Clearances From Ground
----------------------------------------------------------------------------------------------------------------
                                     Installations built before August 13,     Installations built on or after
                                                      2007                             August 13, 2007
              Distance              ----------------------------------------------------------------------------
                                       Maximum voltage       Conditions      Voltage to ground     Conditions
----------------------------------------------------------------------------------------------------------------
3.05 m (10.0 ft)...................  <  600 V...........  Above finished     <  150 V...........  Above finished
                                                          grade or                               grade or
                                                          sidewalks, or                          sidewalks, or
                                                          from any                               from any
                                                          platform or                            platform or
                                                          projection from                        projection from
                                                          which they might                       which they
                                                          be reached. (If                        might be
                                                          these areas are                        reached. (If
                                                          accessible to                          these areas are
                                                          other than                             accessible to
                                                          pedestrian                             other than
                                                          traffic, then                          pedestrian
                                                          one of the other                       traffic, then
                                                          conditions                             one of the
                                                          applies).                              other
                                                                                conditions
                                                                                applies.)
3.66 m (12.0 ft)...................  <  600 V...........  Over areas, other  <  300 V...........  Over residential
                                                          than public                            property and
                                                          streets, alleys,                       driveways. Over
                                                          roads, and                             commercial
                                                          driveways,                             areas subject
                                                          subject to                             to pedestrian
                                                          vehicular                              traffic or to
                                                          traffic other                          vehicular
                                                          than truck                             traffic other
                                                          traffic.                               than truck
                                                                                traffic. (This
                                                                                category
                                                                                includes
                                                                                conditions
                                                                                covered under
                                                                                the 3.05-m
                                                                                (10.0-ft)
                                                                                category where
                                                                                the voltage
                                                                                exceeds 150 V.)
4.57 m (15.0 ft)...................  <  600 V...........  Over areas, other  301 to 600 V......  Over residential
                                                          than public                            property and
                                                          streets, alleys,                       driveways. Over
                                                          roads, and                             commercial
                                                          driveways,                             areas subject
                                                          subject to truck                       to pedestrian
                                                          traffic.                               traffic or to
                                                                                vehicular
                                                                                traffic other
                                                                                than truck
                                                                                traffic. (This
                                                                                category
                                                                                includes
                                                                                conditions
                                                                                covered under
                                                                                the 3.05-m
                                                                                (10.0-ft)
                                                                                category where
                                                                                the voltage
                                                                                exceeds 300 V.)
5.49 m (18.0 ft)...................  <  600 V...........  Over public        <  600 V...........  Over public
                                                          streets, alleys,                       streets,
                                                          roads, and                             alleys, roads,
                                                          driveways.                             and driveways.
                                                                                Over commercial
                                                                                areas subject
                                                                                to truck
                                                                                traffic. Other
                                                                                land traversed
                                                                                by vehicles,
                                                                                including land
                                                                                used for
                                                                                cultivating or
                                                                                grazing and
                                                                                forests and
                                                                                orchards.
----------------------------------------------------------------------------------------------------------------

    (3) Clearance from building openings. (i) Service conductors
installed as open conductors or multiconductor cable without an overall
outer jacket shall have a clearance of not less than 914 mm (3.0 ft)
from windows that are designed to be opened, doors, porches, balconies,
ladders, stairs, fire escapes, and similar locations. However,
conductors that run above the top level of a window may be less than
914 mm (3.0 ft) from the window. Vertical clearance of final spans
above, or within 914 mm (3.0 ft) measured horizontally of, platforms,
projections, or surfaces from which they might be reached shall be
maintained in accordance with paragraph (c)(2) of this section.
    (ii) Overhead service conductors may not be installed beneath
openings through which materials may be moved,

such as openings in farm and commercial buildings, and may not be
installed where they will obstruct entrance to these building openings.
    (4) Above roofs. Overhead spans of open conductors and open
multiconductor cables shall have a vertical clearance of not less than
2.44 m (8.0 ft) above the roof surface. The vertical clearance above
the roof level shall be maintained for a distance not less than 914 mm
(3.0 ft) in all directions from the edge of the roof.
    (i) The area above a roof surface subject to pedestrian or
vehicular traffic shall have a vertical clearance from the roof surface
in accordance with the clearance requirements of paragraph (c)(2) of
this section.
    (ii) A reduction in clearance to 914 mm (3.0 ft) is permitted where
the voltage between conductors does not exceed 300 and the roof has a
slope of 102 mm (4 in.) in 305 mm (12 in.) or greater.
    (iii) A reduction in clearance above only the overhanging portion
of the roof to not less than 457 mm (18 in.) is permitted where the
voltage between conductors does not exceed 300 if:
    (A) The conductors do not pass above the roof overhang for a
distance of more than 1.83 m (6.0 ft), 1.22 m (4.0 ft) horizontally,
and
    (B) The conductors are terminated at a through-the-roof raceway or
approved support.
    (iv) The requirement for maintaining a vertical clearance of 914 mm
(3.0 ft) from the edge of the roof does not apply to the final
conductor span, where the conductors are attached to the side of a
building.
    (d) Location of outdoor lamps. Lamps for outdoor lighting shall be
located below all energized conductors, transformers, or other electric
equipment, unless such equipment is controlled by a disconnecting means
that can be locked in the open position, or unless adequate clearances
or other safeguards are provided for relamping operations.
    (e) Services--(1) Disconnecting means. (i) Means shall be provided
to disconnect all conductors in a building or other structure from the
service-entrance conductors. The service disconnecting means shall
plainly indicate whether it is in the open or closed position and shall
be installed at a readily accessible location nearest the point of
entrance of the service-entrance conductors.
    (ii) Each service disconnecting means shall simultaneously
disconnect all ungrounded conductors.
    (iii) Each service disconnecting means shall be suitable for the
prevailing conditions.
    (2) Services over 600 volts, nominal. The following additional
requirements apply to services over 600 volts, nominal.
    (i) Service-entrance conductors installed as open wires shall be
guarded to make them accessible only to qualified persons.
    (ii) Signs warning of high voltage shall be posted where
unqualified employees might come in contact with live parts.
    (f) Overcurrent protection--(1) 600 volts, nominal, or less. The
following requirements apply to overcurrent protection of circuits
rated 600 volts, nominal, or less.
    (i) Conductors and equipment shall be protected from overcurrent in
accordance with their ability to safely conduct current.
    (ii) Except for motor running overload protection, overcurrent
devices may not interrupt the continuity of the grounded conductor
unless all conductors of the circuit are opened simultaneously.
    (iii) A disconnecting means shall be provided on the supply side of
all fuses in circuits over 150 volts to ground and cartridge fuses in
circuits of any voltage where accessible to other than qualified
persons so that each individual circuit containing fuses can be
independently disconnected from the source of power. However, a
current-limiting device without a disconnecting means is permitted on
the supply side of the service disconnecting means. In addition, a
single disconnecting means is permitted on the supply side of more than
one set of fuses as permitted by the exception in Sec.
1910.305(j)(4)(vi) for group operation of motors, and a single
disconnecting means is permitted for fixed electric space-heating
equipment.
    (iv) Overcurrent devices shall be readily accessible to each
employee or authorized building management personnel. These overcurrent
devices may not be located where they will be exposed to physical
damage or in the vicinity of easily ignitable material.
    (v) Fuses and circuit breakers shall be so located or shielded that
employees will not be burned or otherwise injured by their operation.
Handles or levers of circuit breakers, and similar parts that may move
suddenly in such a way that persons in the vicinity are likely to be
injured by being struck by them, shall be guarded or isolated.
    (vi) Circuit breakers shall clearly indicate whether they are in
the open (off) or closed (on) position.
    (vii) Where circuit breaker handles on switchboards are operated
vertically rather than horizontally or rotationally, the up position of
the handle shall be the closed (on) position.
    (viii) Circuit breakers used as switches in 120-volt and 277-volt,
fluorescent lighting circuits shall be listed and marked ``SWD.''
    (ix) A circuit breaker with a straight voltage rating, such as 240
V or 480 V, may only be installed in a circuit in which the nominal
voltage between any two conductors does not exceed the circuit
breaker's voltage rating. A two-pole circuit breaker may not be used
for protecting a 3-phase, corner-grounded delta circuit unless the
circuit breaker is marked 1[Phi]--3[Phi] to indicate such suitability.
A circuit breaker with a slash rating, such as 120/240 V or 480Y/277 V,
may only be installed in a circuit where the nominal voltage of any
conductor to ground does not exceed the lower of the two values of the
circuit breaker's voltage rating and the nominal voltage between any
two conductors does not exceed the higher value of the circuit
breaker's voltage rating.
    (2) Feeders and branch circuits over 600 volts, nominal. The
following requirements apply to feeders and branch circuits energized
at more than 600 volts, nominal:
    (i) Feeder and branch-circuit conductors shall have overcurrent
protection in each ungrounded conductor located at the point where the
conductor receives its supply or at a location in the circuit
determined under engineering supervision;
    (A) Circuit breakers used for overcurrent protection of three-phase
circuits shall have a minimum of three overcurrent relays operated from
three current transformers. On three-phase, three-wire circuits, an
overcurrent relay in the residual circuit of the current transformers
may replace one of the phase relays. An overcurrent relay, operated
from a current transformer that links all phases of a three-phase,
three-wire circuit, may replace the residual relay and one other phase-
conductor current transformer. Where the neutral is not grounded on the
load side of the circuit, the current transformer may link all three
phase conductors and the grounded circuit conductor (neutral); and
    (B) If fuses are used for overcurrent protection, a fuse shall be
connected in series with each ungrounded conductor;
    (ii) Each protective device shall be capable of detecting and
interrupting all values of current that can occur at its location in
excess of its trip setting or melting point;
    (iii) The operating time of the protective device, the available
short-circuit current, and the conductor used

shall be coordinated to prevent damaging or dangerous temperatures in
conductors or conductor insulation under short-circuit conditions; and
    (iv) The following additional requirements apply to feeders only:
    (A) The continuous ampere rating of a fuse may not exceed three
times the ampacity of the conductors. The long-time trip element
setting of a breaker or the minimum trip setting of an electronically
actuated fuse may not exceed six times the ampacity of the conductor.
For fire pumps, conductors may be protected for short circuit only; and
    (B) Conductors tapped to a feeder may be protected by the feeder
overcurrent device where that overcurrent device also protects the tap
conductor.
    (g) Grounding. Paragraphs (g)(1) through (g)(9) of this section
contain grounding requirements for systems, circuits, and equipment.
    (1) Systems to be grounded. Systems that supply premises wiring
shall be grounded as follows:
    (i) All 3-wire dc systems shall have their neutral conductor
grounded;
    (ii) Two-wire dc systems operating at over 50 volts through 300
volts between conductors shall be grounded unless:
    (A) They supply only industrial equipment in limited areas and are
equipped with a ground detector;
    (B) They are rectifier-derived from an ac system complying with
paragraphs (g)(1)(iii), (g)(1)(iv), and (g)(1)(v) of this section; or
    (C) They are fire-alarm circuits having a maximum current of 0.030
amperes;
    (iii) AC circuits of less than 50 volts shall be grounded if they
are installed as overhead conductors outside of buildings or if they
are supplied by transformers and the transformer primary supply system
is ungrounded or exceeds 150 volts to ground;
    (iv) AC systems of 50 volts to 1000 volts shall be grounded under
any of the following conditions, unless exempted by paragraph (g)(1)(v)
of this section:
    (A) If the system can be so grounded that the maximum voltage to
ground on the ungrounded conductors does not exceed 150 volts;
    (B) If the system is nominally rated three-phase, four-wire wye
connected in which the neutral is used as a circuit conductor;
    (C) If the system is nominally rated three-phase, four-wire delta
connected in which the midpoint of one phase is used as a circuit
conductor; or
    (D) If a service conductor is uninsulated;
    (v) AC systems of 50 volts to 1000 volts are not required to be
grounded under any of the following conditions:
    (A) If the system is used exclusively to supply industrial electric
furnaces for melting, refining, tempering, and the like;
    (B) If the system is separately derived and is used exclusively for
rectifiers supplying only adjustable speed industrial drives;
    (C) If the system is separately derived and is supplied by a
transformer that has a primary voltage rating less than 1000 volts,
provided all of the following conditions are met:
    (1) The system is used exclusively for control circuits;
    (2) The conditions of maintenance and supervision ensure that only
qualified persons will service the installation;
    (3) Continuity of control power is required; and
    (4) Ground detectors are installed on the control system;
    (D) If the system is an isolated power system that supplies
circuits in health care facilities; or
    (E) If the system is a high-impedance grounded neutral system in
which a grounding impedance, usually a resistor, limits the ground-
fault current to a low value for 3-phase ac systems of 480 volts to
1000 volts provided all of the following conditions are met:
    (1) The conditions of maintenance and supervision ensure that only
qualified persons will service the installation;
    (2) Continuity of power is required;
    (3) Ground detectors are installed on the system; and
    (4) Line-to-neutral loads are not served.
    (2) Conductor to be grounded. The conductor to be grounded for ac
premises wiring systems required to be grounded by paragraph (g)(1) of
this section shall be as follows:
    (i) One conductor of a single-phase, two-wire system shall be
grounded;
    (ii) The neutral conductor of a single-phase, three-wire system
shall be grounded;
    (iii) The common conductor of a multiphase system having one wire
common to all phases shall be grounded;
    (iv) One phase conductor of a multiphase system where one phase is
grounded shall be grounded; and
    (v) The neutral conductor of a multiphase system in which one phase
is used as a neutral conductor shall be grounded.
    (3) Portable and vehicle-mounted generators. (i) The frame of a
portable generator need not be grounded and may serve as the grounding
electrode for a system supplied by the generator under the following
conditions:
    (A) The generator supplies only equipment mounted on the generator
or cord- and plug-connected equipment through receptacles mounted on
the generator, or both; and
    (B) The noncurrent-carrying metal parts of equipment and the
equipment grounding conductor terminals of the receptacles are bonded
to the generator frame.
    (ii) The frame of a vehicle need not be grounded and may serve as
the grounding electrode for a system supplied by a generator located on
the vehicle under the following conditions:
    (A) The frame of the generator is bonded to the vehicle frame;
    (B) The generator supplies only equipment located on the vehicle
and cord- and plug-connected equipment through receptacles mounted on
the vehicle;
    (C) The noncurrent-carrying metal parts of equipment and the
equipment grounding conductor terminals of the receptacles are bonded
to the generator frame; and
    (D) The system complies with all other provisions of paragraph (g)
of this section.
    (iii) A system conductor that is required to be grounded by the
provisions of paragraph (g)(2) of this section shall be bonded to the
generator frame where the generator is a component of a separately
derived system.
    (4) Grounding connections. (i) For a grounded system, a grounding
electrode conductor shall be used to connect both the equipment
grounding conductor and the grounded circuit conductor to the grounding
electrode. Both the equipment grounding conductor and the grounding
electrode conductor shall be connected to the grounded circuit
conductor on the supply side of the service disconnecting means or on
the supply side of the system disconnecting means or overcurrent
devices if the system is separately derived.
    (ii) For an ungrounded service-supplied system, the equipment
grounding conductor shall be connected to the grounding electrode
conductor at the service equipment. For an ungrounded separately
derived system, the equipment grounding conductor shall be connected to
the grounding electrode conductor at, or ahead of, the system
disconnecting means or overcurrent devices.
    (iii) On extensions of existing branch circuits that do not have an
equipment grounding conductor, grounding-type receptacles may be
grounded to a grounded cold water pipe near the equipment if the
extension was installed before August 13, 2007. When any

element of this branch circuit is replaced, the entire branch circuit
shall use an equipment grounding conductor that complies with all other
provisions of paragraph (g) of this section.
    (5) Grounding path. The path to ground from circuits, equipment,
and enclosures shall be permanent, continuous, and effective.
    (6) Supports, enclosures, and equipment to be grounded. (i) Metal
cable trays, metal raceways, and metal enclosures for conductors shall
be grounded, except that:
    (A) Metal enclosures such as sleeves that are used to protect cable
assemblies from physical damage need not be grounded; and
    (B) Metal enclosures for conductors added to existing installations
of open wire, knob-and-tube wiring, and nonmetallic-sheathed cable need
not be grounded if all of the following conditions are met:
    (1) Runs are less than 7.62 meters (25.0 ft);
    (2) Enclosures are free from probable contact with ground, grounded
metal, metal laths, or other conductive materials; and
    (3) Enclosures are guarded against employee contact.
    (ii) Metal enclosures for service equipment shall be grounded.
    (iii) Frames of electric ranges, wall-mounted ovens, counter-
mounted cooking units, clothes dryers, and metal outlet or junction
boxes that are part of the circuit for these appliances shall be
grounded.
    (iv) Exposed noncurrent-carrying metal parts of fixed equipment
that may become energized shall be grounded under any of the following
conditions:
    (A) If within 2.44 m (8 ft) vertically or 1.52 m (5 ft)
horizontally of ground or grounded metal objects and subject to
employee contact;
    (B) If located in a wet or damp location and not isolated;
    (C) If in electrical contact with metal;
    (D) If in a hazardous (classified) location;
    (E) If supplied by a metal-clad, metal-sheathed, or grounded metal
raceway wiring method; or
    (F) If equipment operates with any terminal at over 150 volts to
ground.
    (v) Notwithstanding the provisions of paragraph (g)(6)(iv) of this
section, exposed noncurrent-carrying metal parts of the following types
of fixed equipment need not be grounded:
    (A) Enclosures for switches or circuit breakers used for other than
service equipment and accessible to qualified persons only;
    (B) Electrically heated appliances that are permanently and
effectively insulated from ground;
    (C) Distribution apparatus, such as transformer and capacitor
cases, mounted on wooden poles, at a height exceeding 2.44 m (8.0 ft)
above ground or grade level; and
    (D) Listed equipment protected by a system of double insulation, or
its equivalent, and distinctively marked as such.
    (vi) Exposed noncurrent-carrying metal parts of cord- and plug-
connected equipment that may become energized shall be grounded under
any of the following conditions:
    (A) If in hazardous (classified) locations (see Sec.  1910.307);
    (B) If operated at over 150 volts to ground, except for guarded
motors and metal frames of electrically heated appliances if the
appliance frames are permanently and effectively insulated from ground;
    (C) If the equipment is of the following types:
    (1) Refrigerators, freezers, and air conditioners;
    (2) Clothes-washing, clothes-drying, and dishwashing machines, sump
pumps, and electric aquarium equipment;
    (3) Hand-held motor-operated tools, stationary and fixed motor-
operated tools, and light industrial motor-operated tools;
    (4) Motor-operated appliances of the following types: hedge
clippers, lawn mowers, snow blowers, and wet scrubbers;
    (5) Cord- and plug-connected appliances used in damp or wet
locations, or by employees standing on the ground or on metal floors or
working inside of metal tanks or boilers;
    (6) Portable and mobile X-ray and associated equipment;
    (7) Tools likely to be used in wet and conductive locations; and
    (8) Portable hand lamps.
    (vii) Notwithstanding the provisions of paragraph (g)(6)(vi) of
this section, the following equipment need not be grounded:
    (A) Tools likely to be used in wet and conductive locations if
supplied through an isolating transformer with an ungrounded secondary
of not over 50 volts; and
    (B) Listed or labeled portable tools and appliances if protected by
an approved system of double insulation, or its equivalent, and
distinctively marked.
    (7) Nonelectrical equipment. The metal parts of the following
nonelectrical equipment shall be grounded: frames and tracks of
electrically operated cranes and hoists; frames of nonelectrically
driven elevator cars to which electric conductors are attached; hand-
operated metal shifting ropes or cables of electric elevators; and
metal partitions, grill work, and similar metal enclosures around
equipment of over 750 volts between conductors.
    (8) Methods of grounding fixed equipment. (i) Noncurrent-carrying
metal parts of fixed equipment, if required to be grounded by this
subpart, shall be grounded by an equipment grounding conductor that is
contained within the same raceway, cable, or cord, or runs with or
encloses the circuit conductors. For dc circuits only, the equipment
grounding conductor may be run separately from the circuit conductors.
    (ii) Electric equipment is considered to be effectively grounded if
it is secured to, and in electrical contact with, a metal rack or
structure that is provided for its support and the metal rack or
structure is grounded by the method specified for the noncurrent-
carrying metal parts of fixed equipment in paragraph (g)(8)(i) of this
section. Metal car frames supported by metal hoisting cables attached
to or running over metal sheaves or drums of grounded elevator machines
are also considered to be effectively grounded.
    (iii) For installations made before April 16, 1981, electric
equipment is also considered to be effectively grounded if it is
secured to, and in metallic contact with, the grounded structural metal
frame of a building. When any element of this branch circuit is
replaced, the entire branch circuit shall use an equipment grounding
conductor that complies with all other provisions of paragraph (g) of
this section.
    (9) Grounding of systems and circuits of 1000 volts and over (high
voltage). If high voltage systems are grounded, they shall comply with
all applicable provisions of paragraphs (g)(1) through (g)(8) of this
section as supplemented and modified by the following requirements:
    (i) Systems supplying portable or mobile high voltage equipment,
other than substations installed on a temporary basis, shall comply
with the following:
    (A) The system shall have its neutral grounded through an
impedance. If a delta-connected high voltage system is used to supply
the equipment, a system neutral shall be derived.
    (B) Exposed noncurrent-carrying metal parts of portable and mobile
equipment shall be connected by an equipment grounding conductor to the
point at which the system neutral impedance is grounded.
    (C) Ground-fault detection and relaying shall be provided to

automatically deenergize any high voltage system component that has
developed a ground fault. The continuity of the equipment grounding
conductor shall be continuously monitored so as to deenergize
automatically the high voltage feeder to the portable equipment upon
loss of continuity of the equipment grounding conductor.
    (D) The grounding electrode to which the portable equipment system
neutral impedance is connected shall be isolated from and separated in
the ground by at least 6.1 m (20.0 ft) from any other system or
equipment grounding electrode, and there shall be no direct connection
between the grounding electrodes, such as buried pipe, fence, and so
forth.
    (ii) All noncurrent-carrying metal parts of portable equipment and
fixed equipment, including their associated fences, housings,
enclosures, and supporting structures, shall be grounded. However,
equipment that is guarded by location and isolated from ground need not
be grounded. Additionally, pole-mounted distribution apparatus at a
height exceeding 2.44 m (8.0 ft) above ground or grade level need not
be grounded.

Sec.  1910.305  Wiring methods, components, and equipment for general
use.

    (a) Wiring methods. The provisions of this section do not apply to
conductors that are an integral part of factory-assembled equipment.
    (1) General requirements. (i) Metal raceways, cable trays, cable
armor, cable sheath, enclosures, frames, fittings, and other metal
noncurrent-carrying parts that are to serve as grounding conductors,
with or without the use of supplementary equipment grounding
conductors, shall be effectively bonded where necessary to ensure
electrical continuity and the capacity to conduct safely any fault
current likely to be imposed on them. Any nonconductive paint, enamel,
or similar coating shall be removed at threads, contact points, and
contact surfaces or be connected by means of fittings designed so as to
make such removal unnecessary.
    (ii) Where necessary for the reduction of electrical noise
(electromagnetic interference) of the grounding circuit, an equipment
enclosure supplied by a branch circuit may be isolated from a raceway
containing circuits supplying only that equipment by one or more listed
nonmetallic raceway fittings located at the point of attachment of the
raceway to the equipment enclosure. The metal raceway shall be
supplemented by an internal insulated equipment grounding conductor
installed to ground the equipment enclosure.
    (iii) No wiring systems of any type may be installed in ducts used
to transport dust, loose stock, or flammable vapors. No wiring system
of any type may be installed in any duct used for vapor removal or for
ventilation of commercial-type cooking equipment, or in any shaft
containing only such ducts.
    (2) Temporary wiring. Except as specifically modified in this
paragraph, all other requirements of this subpart for permanent wiring
shall also apply to temporary wiring installations.
    (i) Temporary electrical power and lighting installations of 600
volts, nominal, or less may be used only as follows:
    (A) During and for remodeling, maintenance, or repair of buildings,
structures, or equipment, and similar activities;
    (B) For a period not to exceed 90 days for Christmas decorative
lighting, carnivals, and similar purposes; or
    (C) For experimental or development work, and during emergencies.
    (ii) Temporary wiring shall be removed immediately upon completion
of the project or purpose for which the wiring was installed.
    (iii) Temporary electrical installations of more than 600 volts may
be used only during periods of tests, experiments, emergencies, or
construction-like activities.
    (iv) The following requirements apply to feeders:
    (A) Feeders shall originate in an approved distribution center.
    (B) Conductors shall be run as multiconductor cord or cable
assemblies. However, if installed as permitted in paragraph
(a)(2)(i)(C) of this section, and if accessible only to qualified
persons, feeders may be run as single insulated conductors.
    (v) The following requirements apply to branch circuits:
    (A) Branch circuits shall originate in an approved power outlet or
panelboard.
    (B) Conductors shall be multiconductor cord or cable assemblies or
open conductors. If run as open conductors, they shall be fastened at
ceiling height every 3.05 m (10.0 ft).
    (C) No branch-circuit conductor may be laid on the floor.
    (D) Each branch circuit that supplies receptacles or fixed
equipment shall contain a separate equipment grounding conductor if run
as open conductors.
    (vi) Receptacles shall be of the grounding type. Unless installed
in a continuous grounded metallic raceway or metallic covered cable,
each branch circuit shall contain a separate equipment grounding
conductor and all receptacles shall be electrically connected to the
grounding conductor.
    (vii) No bare conductors nor earth returns may be used for the
wiring of any temporary circuit.
    (viii) Suitable disconnecting switches or plug connectors shall be
installed to permit the disconnection of all ungrounded conductors of
each temporary circuit. Multiwire branch circuits shall be provided
with a means to disconnect simultaneously all ungrounded conductors at
the power outlet or panelboard where the branch circuit originated.

    Note to paragraph (a)(2)(viii) of this section. Circuit breakers
with their handles connected by approved handle ties are considered
a single disconnecting means for the purpose of this requirement.

    (ix) All lamps for general illumination shall be protected from
accidental contact or breakage by a suitable fixture or lampholder with
a guard. Brass shell, paper-lined sockets, or other metal-cased sockets
may not be used unless the shell is grounded.
    (x) Flexible cords and cables shall be protected from accidental
damage, as might be caused, for example, by sharp corners, projections,
and doorways or other pinch points.
    (xi) Cable assemblies and flexible cords and cables shall be
supported in place at intervals that ensure that they will be protected
from physical damage. Support shall be in the form of staples, cables
ties, straps, or similar type fittings installed so as not to cause
damage.
    (3) Cable trays. (i) Only the following wiring methods may be
installed in cable tray systems: armored cable; electrical metallic
tubing; electrical nonmetallic tubing; fire alarm cables; flexible
metal conduit; flexible metallic tubing; instrumentation tray cable;
intermediate metal conduit; liquidtight flexible metal conduit;
liquidtight flexible nonmetallic conduit; metal-clad cable; mineral-
insulated, metal-sheathed cable; multiconductor service-entrance cable;
multiconductor underground feeder and branch-circuit cable;
multipurpose and communications cables; nonmetallic-sheathed cable;
power and control tray cable; power-limited tray cable; optical fiber
cables; and other factory-assembled, multiconductor control, signal, or
power cables that are specifically approved for installation in cable
trays, rigid metal conduit, and rigid nonmetallic conduit.
    (ii) In industrial establishments where conditions of maintenance
and supervision assure that only qualified persons will service the
installed cable

tray system, the following cables may also be installed in ladder,
ventilated-trough, or ventilated-channel cable trays:
    (A) Single conductor cable; the cable shall be No. 1/0 or larger
and shall be of a type listed and marked on the surface for use in
cable trays; where Nos. 1/0 through 4/0 single conductor cables are
installed in ladder cable tray, the maximum allowable rung spacing for
the ladder cable tray shall be 229 mm (9 in.); where exposed to direct
rays of the sun, cables shall be identified as being sunlight
resistant;
    (B) Welding cables installed in dedicated cable trays;
    (C) Single conductors used as equipment grounding conductors; these
conductors, which may be insulated, covered, or bare, shall be No. 4 or
larger; and
    (D) Multiconductor cable, Type MV; where exposed to direct rays of
the sun, the cable shall be identified as being sunlight resistant.
    (iii) Metallic cable trays may be used as equipment grounding
conductors only where continuous maintenance and supervision ensure
that qualified persons will service the installed cable tray system.
    (iv) Cable trays in hazardous (classified) locations may contain
only the cable types permitted in such locations. (See Sec.  1910.307.)
    (v) Cable tray systems may not be used in hoistways or where
subjected to severe physical damage.
    (4) Open wiring on insulators. (i) Open wiring on insulators is
only permitted on systems of 600 volts, nominal, or less for industrial
or agricultural establishments, indoors or outdoors, in wet or dry
locations, where subject to corrosive vapors, and for services.
    (ii) Conductors smaller than No. 8 shall be rigidly supported on
noncombustible, nonabsorbent insulating materials and may not contact
any other objects. Supports shall be installed as follows:
    (A) Within 152 mm (6 in.) from a tap or splice;
    (B) Within 305 mm (12 in.) of a dead-end connection to a lampholder
or receptacle; and
    (C) At intervals not exceeding 1.37 m (4.5 ft), and at closer
intervals sufficient to provide adequate support where likely to be
disturbed.
    (iii) In dry locations, where not exposed to severe physical
damage, conductors may be separately enclosed in flexible nonmetallic
tubing. The tubing shall be in continuous lengths not exceeding 4.57 m
(15.0 ft) and secured to the surface by straps at intervals not
exceeding 1.37 m (4.5 ft).
    (iv) Open conductors shall be separated from contact with walls,
floors, wood cross members, or partitions through which they pass by
tubes or bushings of noncombustible, nonabsorbent insulating material.
If the bushing is shorter than the hole, a waterproof sleeve of
nonconductive material shall be inserted in the hole and an insulating
bushing slipped into the sleeve at each end in such a manner as to keep
the conductors absolutely out of contact with the sleeve. Each
conductor shall be carried through a separate tube or sleeve.
    (v) Where open conductors cross ceiling joints and wall studs and
are exposed to physical damage (for example, located within 2.13 m (7.0
ft) of the floor), they shall be protected.
    (b) Cabinets, boxes, and fittings--(1) Conductors entering boxes,
cabinets, or fittings. (i) Conductors entering cutout boxes, cabinets,
or fittings shall be protected from abrasion, and openings through
which conductors enter shall be effectively closed.
    (ii) Unused openings in cabinets, boxes, and fittings shall be
effectively closed.
    (iii) Where cable is used, each cable shall be secured to the
cabinet, cutout box, or meter socket enclosure. However, where cable
with an entirely nonmetallic sheath enters the top of a surface-mounted
enclosure through one or more nonflexible raceways not less than 457 mm
(18 in.) or more than 3.05 m (10.0 ft) in length, the cable need not be
secured to the cabinet, box, or enclosure provided all of the following
conditions are met:
    (A) Each cable is fastened within 305 mm (12 in.) of the outer end
of the raceway, measured along the sheath;
    (B) The raceway extends directly above the enclosure and does not
penetrate a structural ceiling;
    (C) A fitting is provided on each end of the raceway to protect the
cable from abrasion, and the fittings remain accessible after
installation;
    (D) The raceway is sealed or plugged at the outer end using
approved means so as to prevent access to the enclosure through the
raceway;
    (E) The cable sheath is continuous through the raceway and extends
into the enclosure not less than 6.35 mm (0.25 in.) beyond the fitting;
    (F) The raceway is fastened at its outer end and at other points as
necessary; and
    (G) Where installed as conduit or tubing, the allowable cable fill
does not exceed that permitted for complete conduit or tubing systems.
    (2) Covers and canopies. (i) All pull boxes, junction boxes, and
fittings shall be provided with covers identified for the purpose. If
metal covers are used, they shall be grounded. In completed
installations, each outlet box shall have a cover, faceplate, or
fixture canopy. Covers of outlet boxes having holes through which
flexible cord pendants pass shall be provided with bushings designed
for the purpose or shall have smooth, well-rounded surfaces on which
the cords may bear.
    (ii) Where a fixture canopy or pan is used, any combustible wall or
ceiling finish exposed between the edge of the canopy or pan and the
outlet box shall be covered with noncombustible material.
    (3) Pull and junction boxes for systems over 600 volts, nominal. In
addition to other requirements in this section, the following
requirements apply to pull and junction boxes for systems over 600
volts, nominal:
    (i) Boxes shall provide a complete enclosure for the contained
conductors or cables.
    (ii) Boxes shall be closed by suitable covers securely fastened in
place.

    Note to paragraph (b)(3)(ii) of this section: Underground box
covers that weigh over 45.4 kg (100 lbs) meet this requirement.

    (iii) Covers for boxes shall be permanently marked ``HIGH
VOLTAGE.'' The marking shall be on the outside of the box cover and
shall be readily visible and legible.
    (c) Switches--(1) Single-throw knife switches. Single-throw knife
switches shall be so placed that gravity will not tend to close them.
Single-throw knife switches approved for use in the inverted position
shall be provided with a locking device that will ensure that the
blades remain in the open position when so set.
    (2) Double-throw knife switches. Double-throw knife switches may be
mounted so that the throw will be either vertical or horizontal.
However, if the throw is vertical, a locking device shall be provided
to ensure that the blades remain in the open position when so set.
    (3) Connection of switches. (i) Single-throw knife switches and
switches with butt contacts shall be connected so that the blades are
deenergized when the switch is in the open position.
    (ii) Single-throw knife switches, molded-case switches, switches
with butt contacts, and circuit breakers used as switches shall be
connected so that the terminals supplying the load are deenergized when
the switch is in the open position. However, blades and terminals
supplying the load of a switch

may be energized when the switch is in the open position where the
switch is connected to circuits or equipment inherently capable of
providing a backfeed source of power. For such installations, a
permanent sign shall be installed on the switch enclosure or
immediately adjacent to open switches that read, ``WARNING--LOAD SIDE
TERMINALS MAY BE ENERGIZED BY BACKFEED.''
    (4) Faceplates for flush-mounted snap switches. Snap switches
mounted in boxes shall have faceplates installed so as to completely
cover the opening and seat against the finished surface.
    (5) Grounding. Snap switches, including dimmer switches, shall be
effectively grounded and shall provide a means to ground metal
faceplates, whether or not a metal faceplate is installed. However, if
no grounding means exists within the snap-switch enclosure, or where
the wiring method does not include or provide an equipment ground, a
snap switch without a grounding connection is permitted for replacement
purposes only. Such snap switches shall be provided with a faceplate of
nonconducting, noncombustible material if they are located within reach
of conducting floors or other conducting surfaces.
    (d) Switchboards and panelboards--(1) Switchboards with exposed
live parts. Switchboards that have any exposed live parts shall be
located in permanently dry locations and shall be accessible only to
qualified persons.
    (2) Panelboard enclosures. Panelboards shall be mounted in
cabinets, cutout boxes, or enclosures designed for the purpose and
shall be dead front. However, panelboards other than the dead front
externally-operable type are permitted where accessible only to
qualified persons.
    (3) Knife switches mounted in switchboards or panelboards. Exposed
blades of knife switches mounted in switchboards or panelboards shall
be dead when open.
    (e) Enclosures for damp or wet locations--(1) Cabinets, cutout
boxes, fittings, boxes, and panelboard enclosures. Cabinets, cutout
boxes, fittings, boxes, and panelboard enclosures in damp or wet
locations shall be installed so as to prevent moisture or water from
entering and accumulating within the enclosures and shall be mounted so
there is at least 6.35-mm (0.25-in.) airspace between the enclosure and
the wall or other supporting surface. However, nonmetallic enclosures
may be installed without the airspace on a concrete, masonry, tile, or
similar surface. The enclosures shall be weatherproof in wet locations.
    (2) Switches, circuit breakers, and switchboards. Switches, circuit
breakers, and switchboards installed in wet locations shall be enclosed
in weatherproof enclosures.
    (f) Conductors for general wiring--(1) Insulation. All conductors
used for general wiring shall be insulated unless otherwise permitted
in this subpart.
    (2) Type. The conductor insulation shall be of a type that is
approved for the voltage, operating temperature, and location of use.
    (3) Distinguishable. Insulated conductors shall be distinguishable
by appropriate color or other suitable means as being grounded
conductors, ungrounded conductors, or equipment grounding conductors.
    (g) Flexible cords and cables--(1)Use of flexible cords and cables.
(i) Flexible cords and cables shall be approved for conditions of use
and location.
    (ii) Flexible cords and cables may be used only for:
    (A) Pendants;
    (B) Wiring of fixtures;
    (C) Connection of portable lamps or appliances;
    (D) Portable and mobile signs;
    (E) Elevator cables;
    (F) Wiring of cranes and hoists;
    (G) Connection of stationary equipment to facilitate their frequent
interchange;
    (H) Prevention of the transmission of noise or vibration;
    (I) Appliances where the fastening means and mechanical connections
are designed to permit removal for maintenance and repair;
    (J) Data processing cables approved as a part of the data
processing system;
    (K) Connection of moving parts; and
    (L) Temporary wiring as permitted in paragraph (a)(2) of this
section.
    (iii) If used as permitted in paragraphs (g)(1)(ii)(C),
(g)(1)(ii)(G), or (g)(1)(ii)(I) of this section, the flexible cord
shall be equipped with an attachment plug and shall be energized from
an approved receptacle outlet.
    (iv) Unless specifically permitted otherwise in paragraph
(g)(1)(ii) of this section, flexible cords and cables may not be used:
    (A) As a substitute for the fixed wiring of a structure;
    (B) Where run through holes in walls, ceilings, or floors;
    (C) Where run through doorways, windows, or similar openings;
    (D) Where attached to building surfaces;
    (E) Where concealed behind building walls, ceilings, or floors; or
    (F) Where installed in raceways, except as otherwise permitted in
this subpart.
    (v) Flexible cords used in show windows and showcases shall be Type
S, SE, SEO, SEOO, SJ, SJE, SJEO, SJEOO, SJO, SJOO, SJT, SJTO, SJTOO,
SO, SOO, ST, STO, or STOO, except for the wiring of chain-supported
lighting fixtures and supply cords for portable lamps and other
merchandise being displayed or exhibited.
    (2) Identification, splices, and terminations. (i) A conductor of a
flexible cord or cable that is used as a grounded conductor or an
equipment grounding conductor shall be distinguishable from other
conductors. Types S, SC, SCE, SCT, SE, SEO, SEOO, SJ, SJE, SJEO, SJEOO,
SJO, SJT, SJTO, SJTOO, SO, SOO, ST, STO, and STOO flexible cords and
Types G, G-GC, PPE, and W flexible cables shall be durably marked on
the surface at intervals not exceeding 610 mm (24 in.) with the type
designation, size, and number of conductors.
    (ii) Flexible cords may be used only in continuous lengths without
splice or tap. Hard-service cord and junior hard-service cord No. 14
and larger may be repaired if spliced so that the splice retains the
insulation, outer sheath properties, and usage characteristics of the
cord being spliced.
    (iii) Flexible cords and cables shall be connected to devices and
fittings so that strain relief is provided that will prevent pull from
being directly transmitted to joints or terminal screws.
    (h) Portable cables over 600 volts, nominal. This paragraph applies
to portable cables used at more than 600 volts, nominal.
    (1) Conductor construction. Multiconductor portable cable for use
in supplying power to portable or mobile equipment at over 600 volts,
nominal, shall consist of No. 8 or larger conductors employing flexible
stranding. However, the minimum size of the insulated ground-check
conductor of Type G-GC cables shall be No. 10.
    (2) Shielding. Cables operated at over 2,000 volts shall be
shielded for the purpose of confining the voltage stresses to the
insulation.
    (3) Equipment grounding conductors. Grounding conductors shall be
provided.
    (4) Grounding shields. All shields shall be grounded.
    (5) Minimum bending radii. The minimum bending radii for portable
cables during installation and handling in service shall be adequate to
prevent damage to the cable.
    (6) Fittings. Connectors used to connect lengths of cable in a run
shall

be of a type that lock firmly together. Provisions shall be made to
prevent opening or closing these connectors while energized. Strain
relief shall be provided at connections and terminations.
    (7) Splices. Portable cables may not be operated with splices
unless the splices are of the permanent molded, vulcanized, or other
approved type.
    (8) Terminations. Termination enclosures shall be suitably marked
with a high voltage hazard warning, and terminations shall be
accessible only to authorized and qualified employees.
    (i) Fixture wires--(1) General. Fixture wires shall be approved for
the voltage, temperature, and location of use. A fixture wire which is
used as a grounded conductor shall be identified.
    (2) Uses permitted. Fixture wires may be used only:
    (i) For installation in lighting fixtures and in similar equipment
where enclosed or protected and not subject to bending or twisting in
use; or
    (ii) For connecting lighting fixtures to the branch-circuit
conductors supplying the fixtures.
    (3) Uses not permitted. Fixture wires may not be used as branch-
circuit conductors except as permitted for Class 1 power limited
circuits and for fire alarm circuits.
    (j) Equipment for general use--(1) Lighting fixtures, lampholders,
lamps, and receptacles. (i) Fixtures, lampholders, lamps, rosettes, and
receptacles may have no live parts normally exposed to employee
contact. However, rosettes and cleat-type lampholders and receptacles
located at least 2.44 m (8.0 ft) above the floor may have exposed
terminals.
    (ii) Handlamps of the portable type supplied through flexible cords
shall be equipped with a handle of molded composition or other material
identified for the purpose, and a substantial guard shall be attached
to the lampholder or the handle. Metal shell, paper-lined lampholders
may not be used.
    (iii) Lampholders of the screw-shell type shall be installed for
use as lampholders only. Where supplied by a circuit having a grounded
conductor, the grounded conductor shall be connected to the screw
shell. Lampholders installed in wet or damp locations shall be of the
weatherproof type.
    (iv) Fixtures installed in wet or damp locations shall be
identified for the purpose and shall be so constructed or installed
that water cannot enter or accumulate in wireways, lampholders, or
other electrical parts.
    (2) Receptacles, cord connectors, and attachment plugs (caps). (i)
All 15- and 20-ampere attachment plugs and connectors shall be
constructed so that there are no exposed current-carrying parts except
the prongs, blades, or pins. The cover for wire terminations shall be a
part that is essential for the operation of an attachment plug or
connector (dead-front construction). Attachment plugs shall be
installed so that their prongs, blades, or pins are not energized
unless inserted into an energized receptacle. No receptacles may be
installed so as to require an energized attachment plug as its source
of supply.
    (ii) Receptacles, cord connectors, and attachment plugs shall be
constructed so that no receptacle or cord connector will accept an
attachment plug with a different voltage or current rating than that
for which the device is intended. However, a 20-ampere T-slot
receptacle or cord connector may accept a 15-ampere attachment plug of
the same voltage rating.
    (iii) Nongrounding-type receptacles and connectors may not be used
for grounding-type attachment plugs.
    (iv) A receptacle installed in a wet or damp location shall be
suitable for the location.
    (v) A receptacle installed outdoors in a location protected from
the weather or in other damp locations shall have an enclosure for the
receptacle that is weatherproof when the receptacle is covered
(attachment plug cap not inserted and receptacle covers closed).

    Note to paragraph (j)(2)(v) of this section. A receptacle is
considered to be in a location protected from the weather when it is
located under roofed open porches, canopies, marquees, or the like
and where it will not be subjected to a beating rain or water
runoff.

    (vi) A receptacle installed in a wet location where the product
intended to be plugged into it is not attended while in use (for
example, sprinkler system controllers, landscape lighting, and holiday
lights) shall have an enclosure that is weatherproof with the
attachment plug cap inserted or removed.
    (vii) A receptacle installed in a wet location where the product
intended to be plugged into it will be attended while in use (for
example, portable tools) shall have an enclosure that is weatherproof
when the attachment plug cap is removed.
    (3) Appliances. (i) Appliances may have no live parts normally
exposed to contact other than parts functioning as open-resistance
heating elements, such as the heating elements of a toaster, which are
necessarily exposed.
    (ii) Each appliance shall have a means to disconnect it from all
ungrounded conductors. If an appliance is supplied by more than one
source, the disconnecting means shall be grouped and identified.
    (iii) Each electric appliance shall be provided with a nameplate
giving the identifying name and the rating in volts and amperes, or in
volts and watts. If the appliance is to be used on a specific frequency
or frequencies, it shall be so marked. Where motor overload protection
external to the appliance is required, the appliance shall be so
marked.
    (iv) Marking shall be located so as to be visible or easily
accessible after installation.
    (4) Motors. This paragraph applies to motors, motor circuits, and
controllers.
    (i) If specified in paragraph (j)(4) of this section that one piece
of equipment shall be ``within sight of'' another piece of equipment,
the piece of equipment shall be visible and not more than 15.24 m (50.0
ft) from the other.
    (ii) An individual disconnecting means shall be provided for each
controller. A disconnecting means shall be located within sight of the
controller location. However, a single disconnecting means may be
located adjacent to a group of coordinated controllers mounted adjacent
to each other on a multi-motor continuous process machine. The
controller disconnecting means for motor branch circuits over 600
volts, nominal, may be out of sight of the controller, if the
controller is marked with a warning label giving the location and
identification of the disconnecting means that is to be locked in the
open position.
    (iii) The disconnecting means shall disconnect the motor and the
controller from all ungrounded supply conductors and shall be so
designed that no pole can be operated independently.
    (iv) The disconnecting means shall plainly indicate whether it is
in the open (off) or closed (on) position.
    (v) The disconnecting means shall be readily accessible. If more
than one disconnect is provided for the same equipment, only one need
be readily accessible.
    (vi) An individual disconnecting means shall be provided for each
motor, but a single disconnecting means may be used for a group of
motors under any one of the following conditions:
    (A) If a number of motors drive several parts of a single machine
or piece of apparatus, such as a metal or woodworking machine, crane,
or hoist;
    (B) If a group of motors is under the protection of one set of
branch-circuit protective devices; or

    (C) If a group of motors is in a single room within sight of the
location of the disconnecting means.
    (vii) Motors, motor-control apparatus, and motor branch-circuit
conductors shall be protected against overheating due to motor
overloads or failure to start, and against short-circuits or ground
faults. These provisions do not require overload protection that will
stop a motor where a shutdown is likely to introduce additional or
increased hazards, as in the case of fire pumps, or where continued
operation of a motor is necessary for a safe shutdown of equipment or
process and motor overload sensing devices are connected to a
supervised alarm.
    (viii) Where live parts of motors or controllers operating at over
150 volts to ground are guarded against accidental contact only by
location, and where adjustment or other attendance may be necessary
during the operation of the apparatus, suitable insulating mats or
platforms shall be provided so that the attendant cannot readily touch
live parts unless standing on the mats or platforms.
    (5) Transformers. (i) Paragraph (j)(5) of this section covers the
installation of all transformers except the following:
    (A) Current transformers;
    (B) Dry-type transformers installed as a component part of other
apparatus;
    (C) Transformers that are an integral part of an X-ray, high
frequency, or electrostatic-coating apparatus;
    (D) Transformers used with Class 2 and Class 3 circuits, sign and
outline lighting, electric discharge lighting, and power-limited fire-
alarm circuits; and
    (E) Liquid-filled or dry-type transformers used for research,
development, or testing, where effective safeguard arrangements are
provided.
    (ii) The operating voltage of exposed live parts of transformer
installations shall be indicated by signs or visible markings on the
equipment or structure.
    (iii) Dry-type, high fire point liquid-insulated, and askarel-
insulated transformers installed indoors and rated over 35kV shall be
in a vault.
    (iv) Oil-insulated transformers installed indoors shall be
installed in a vault.
    (v) Combustible material, combustible buildings and parts of
buildings, fire escapes, and door and window openings shall be
safeguarded from fires that may originate in oil-insulated transformers
attached to or adjacent to a building or combustible material.
    (vi) Transformer vaults shall be constructed so as to contain fire
and combustible liquids within the vault and to prevent unauthorized
access. Locks and latches shall be so arranged that a vault door can be
readily opened from the inside.
    (vii) Any pipe or duct system foreign to the electrical
installation may not enter or pass through a transformer vault.

    Note to paragraph (j)(5)(vii) of this section. Piping or other
facilities provided for vault fire protection, or for transformer
cooling, are not considered foreign to the electrical installation.

    (viii) Material may not be stored in transformer vaults.
    (6) Capacitors. (i) All capacitors, except surge capacitors or
capacitors included as a component part of other apparatus, shall be
provided with an automatic means of draining the stored charge after
the capacitor is disconnected from its source of supply.
    (ii) The following requirements apply to capacitors installed on
circuits operating at more than 600 volts, nominal:
    (A) Group-operated switches shall be used for capacitor switching
and shall be capable of the following:
    (1) Carrying continuously not less than 135 percent of the rated
current of the capacitor installation;
    (2) Interrupting the maximum continuous load current of each
capacitor, capacitor bank, or capacitor installation that will be
switched as a unit;
    (3) Withstanding the maximum inrush current, including
contributions from adjacent capacitor installations; and
    (4) Carrying currents due to faults on the capacitor side of the
switch;
    (B) A means shall be installed to isolate from all sources of
voltage each capacitor, capacitor bank, or capacitor installation that
will be removed from service as a unit. The isolating means shall
provide a visible gap in the electric circuit adequate for the
operating voltage;
    (C) Isolating or disconnecting switches (with no interrupting
rating) shall be interlocked with the load interrupting device or shall
be provided with prominently displayed caution signs to prevent
switching load current; and
    (D) For series capacitors, the proper switching shall be assured by
use of at least one of the following:
    (1) Mechanically sequenced isolating and bypass switches;
    (2) Interlocks; or
    (3) Switching procedure prominently displayed at the switching
location.
    (7) Storage Batteries. Provisions shall be made for sufficient
diffusion and ventilation of gases from storage batteries to prevent
the accumulation of explosive mixtures.

Sec.  1910.306  Specific purpose equipment and installations.

    (a) Electric signs and outline lighting--(1) Disconnecting means.
(i) Each sign and outline lighting system, or feeder circuit or branch
circuit supplying a sign or outline lighting system, shall be
controlled by an externally operable switch or circuit breaker that
will open all ungrounded conductors. However, a disconnecting means is
not required for an exit directional sign located within a building or
for cord-connected signs with an attachment plug.
    (ii) Signs and outline lighting systems located within fountains
shall have the disconnect located at least 1.52 m (5.0 ft) from the
inside walls of the fountain.
    (2) Location. (i) The disconnecting means shall be within sight of
the sign or outline lighting system that it controls. Where the
disconnecting means is out of the line of sight from any section that
may be energized, the disconnecting means shall be capable of being
locked in the open position.
    (ii) Signs or outline lighting systems operated by electronic or
electromechanical controllers located external to the sign or outline
lighting system may have a disconnecting means located within sight of
the controller or in the same enclosure with the controller. The
disconnecting means shall disconnect the sign or outline lighting
system and the controller from all ungrounded supply conductors. It
shall be designed so no pole can be operated independently and shall be
capable of being locked in the open position.
    (iii) Doors or covers giving access to uninsulated parts of indoor
signs or outline lighting exceeding 600 volts and accessible to other
than qualified persons shall either be provided with interlock switches
to disconnect the primary circuit or shall be so fastened that the use
of other than ordinary tools will be necessary to open them.
    (b) Cranes and hoists. This paragraph applies to the installation
of electric equipment and wiring used in connection with cranes,
monorail hoists, hoists, and all runways.
    (1) Disconnecting means for runway conductors. A disconnecting
means shall be provided between the runway contact conductors and the
power supply. Such disconnecting means shall consist of a motor-circuit
switch, circuit breaker, or molded case switch. The disconnecting means
shall open all ungrounded conductors simultaneously and shall be:
    (i) Readily accessible and operable from the ground or floor level;

    (ii) Arranged to be locked in the open position; and
    (iii) Placed within view of the runway contact conductors.
    (2) Disconnecting means for cranes and monorail hoists. (i) Except
as provided in paragraph (b)(2)(iv) of this section, a motor-circuit
switch, molded case switch, or circuit breaker shall be provided in the
leads from the runway contact conductors or other power supply on all
cranes and monorail hoists.
    (ii) The disconnecting means shall be capable of being locked in
the open position.
    (iii) Means shall be provided at the operating station to open the
power circuit to all motors of the crane or monorail hoist where the
disconnecting means is not readily accessible from the crane or
monorail hoist operating station.
    (iv) The disconnecting means may be omitted where a monorail hoist
or hand-propelled crane bridge installation meets all of the following
conditions:
    (A) The unit is controlled from the ground or floor level;
    (B) The unit is within view of the power supply disconnecting
means; and
    (C) No fixed work platform has been provided for servicing the
unit.
    (3) Limit switch. A limit switch or other device shall be provided
to prevent the load block from passing the safe upper limit of travel
of any hoisting mechanism.
    (4) Clearance. The dimension of the working space in the direction
of access to live parts that may require examination, adjustment,
servicing, or maintenance while alive shall be a minimum of 762 mm (2.5
ft). Where controls are enclosed in cabinets, the doors shall either
open at least 90 degrees or be removable.
    (c) Elevators, dumbwaiters, escalators, moving walks, wheelchair
lifts, and stairway chair lifts. The following requirements apply to
elevators, dumbwaiters, escalators, moving walks, wheelchair lifts, and
stairway chair lifts.
    (1) Disconnecting means. Elevators, dumbwaiters, escalators, moving
walks, wheelchair lifts, and stairway chair lifts shall have a single
means for disconnecting all ungrounded main power supply conductors for
each unit.
    (2) Control panels. Control panels not located in the same space as
the drive machine shall be located in cabinets with doors or panels
capable of being locked closed.
    (3) Type. The disconnecting means shall be an enclosed externally
operable fused motor circuit switch or circuit breaker capable of being
locked in the open position. The disconnecting means shall be a listed
device.
    (4) Operation. No provision may be made to open or close this
disconnecting means from any other part of the premises. If sprinklers
are installed in hoistways, machine rooms, or machinery spaces, the
disconnecting means may automatically open the power supply to the
affected elevators prior to the application of water. No provision may
be made to close this disconnecting means automatically (that is, power
may only be restored by manual means).
    (5) Location. The disconnecting means shall be located where it is
readily accessible to qualified persons.
    (i) On elevators without generator field control, the disconnecting
means shall be located within sight of the motor controller. Driving
machines or motion and operation controllers not within sight of the
disconnecting means shall be provided with a manually operated switch
installed in the control circuit adjacent to the equipment in order to
prevent starting. Where the driving machine is located in a remote
machinery space, a single disconnecting means for disconnecting all
ungrounded main power supply conductors shall be provided and be
capable of being locked in the open position.
    (ii) On elevators with generator field control, the disconnecting
means shall be located within sight of the motor controller for the
driving motor of the motor-generator set. Driving machines, motor-
generator sets, or motion and operation controllers not within sight of
the disconnecting means shall be provided with a manually operated
switch installed in the control circuit to prevent starting. The
manually operated switch shall be installed adjacent to this equipment.
Where the driving machine or the motor-generator set is located in a
remote machinery space, a single means for disconnecting all ungrounded
main power supply conductors shall be provided and be capable of being
locked in the open position.
    (iii) On escalators and moving walks, the disconnecting means shall
be installed in the space where the controller is located.
    (iv) On wheelchair lifts and stairway chair lifts, the
disconnecting means shall be located within sight of the motor
controller.
    (6) Identification and signs. (i) Where there is more than one
driving machine in a machine room, the disconnecting means shall be
numbered to correspond to the identifying number of the driving machine
that they control.
    (ii) The disconnecting means shall be provided with a sign to
identify the location of the supply-side overcurrent protective device.
    (7) Single-car and multicar installations. On single-car and
multicar installations, equipment receiving electrical power from more
than one source shall be provided with a disconnecting means for each
source of electrical power. The disconnecting means shall be within
sight of the equipment served.
    (8) Warning sign for multiple disconnecting means. A warning sign
shall be mounted on or next to the disconnecting means where multiple
disconnecting means are used and parts of the controllers remain
energized from a source other than the one disconnected. The sign shall
be clearly legible and shall read ``WARNING--PARTS OF THE CONTROLLER
ARE NOT DEENERGIZED BY THIS SWITCH.''
    (9) Interconnection between multicar controllers. A warning sign
worded as required in paragraph (c)(8) of this section shall be mounted
on or next to the disconnecting means where interconnections between
controllers are necessary for the operation of the system on multicar
installations that remain energized from a source other than the one
disconnected.
    (10) Motor controllers. Motor controllers may be located outside
the spaces otherwise required by paragraph (c) of this section,
provided they are in enclosures with doors or removable panels capable
of being locked closed and the disconnecting means is located adjacent
to or is an integral part of the motor controller. Motor controller
enclosures for escalators or moving walks may be located in the
balustrade on the side located away from the moving steps or moving
treadway. If the disconnecting means is an integral part of the motor
controller, it shall be operable without opening the enclosure.
    (d) Electric welders--disconnecting means--(1) Arc welders. A
disconnecting means shall be provided in the supply circuit for each
arc welder that is not equipped with a disconnect mounted as an
integral part of the welder. The disconnecting means shall be a switch
or circuit breaker, and its rating may not be less than that necessary
to accommodate overcurrent protection.
    (2) Resistance welders. A switch or circuit breaker shall be
provided by which each resistance welder and its control equipment can
be disconnected from the supply circuit. The ampere rating of this
disconnecting means may not be less than the supply conductor ampacity.
The supply circuit switch may be used as the welder

disconnecting means where the circuit supplies only one welder.
    (e) Information technology equipment--(1) Disconnecting means. A
means shall be provided to disconnect power to all electronic equipment
in an information technology equipment room. There shall also be a
similar means to disconnect the power to all dedicated heating,
ventilating, and air-conditioning (HVAC) systems serving the room and
to cause all required fire/smoke dampers to close.
    (2) Grouping. The control for these disconnecting means shall be
grouped and identified and shall be readily accessible at the principal
exit doors. A single means to control both the electronic equipment and
HVAC system is permitted.
    (3) Exception. Integrated electrical systems covered by Sec.
1910.308(g) need not have the disconnecting means required by paragraph
(e)(1) of this section.
    (f) X-Ray equipment. This paragraph applies to X-ray equipment.
    (1) Disconnecting means. (i) A disconnecting means shall be
provided in the supply circuit. The disconnecting means shall be
operable from a location readily accessible from the X-ray control. For
equipment connected to a 120-volt branch circuit of 30 amperes or less,
a grounding-type attachment plug cap and receptacle of proper rating
may serve as a disconnecting means.
    (ii) If more than one piece of equipment is operated from the same
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. The disconnecting means shall be constructed,
enclosed, or located so as to avoid contact by employees with its live
parts.
    (2) Control. The following requirements apply to industrial and
commercial laboratory equipment.
    (i) Radiographic and 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.
    (ii) Diffraction- and irradiation-type equipment shall have a pilot
light, readable meter deflection, or equivalent means to indicate when
the equipment is energized, unless the equipment or installation is
effectively enclosed or is provided with interlocks to prevent access
to live current-carrying parts during operation.
    (g) Induction and dielectric heating equipment. This paragraph
applies to induction and dielectric heating equipment and accessories
for industrial and scientific applications, but not for medical or
dental applications or for appliances.
    (1) Guarding and grounding. (i) The converting apparatus (including
the dc line) and high-frequency electric circuits (excluding the output
circuits and remote-control circuits) shall be completely contained
within enclosures of noncombustible material.
    (ii) All panel controls shall be of dead-front construction.
    (iii) Doors or detachable panels shall be employed for internal
access. Where doors are used giving access to voltages from 500 to 1000
volts ac or dc, either door locks shall be provided or interlocks shall
be installed. Where doors are used giving access to voltages of over
1000 volts ac or dc, either mechanical lockouts with a disconnecting
means to prevent access until circuit parts within the cubicle are
deenergized, or both door interlocking and mechanical door locks, shall
be provided. Detachable panels not normally used for access to such
parts shall be fastened in a manner that will make them difficult to
remove (for example, by requiring the use of tools).
    (iv) Warning labels or signs that read ``DANGER--HIGH VOLTAGE--KEEP
OUT'' shall be attached to the equipment and shall be plainly visible
where persons might contact energized parts when doors are opened or
closed or when panels are removed from compartments containing over 250
volts ac or dc.
    (v) Induction and dielectric heating equipment shall be protected
as follows:
    (A) Protective cages or adequate shielding shall be used to guard
work applicators other than induction heating coils.
    (B) Induction heating coils shall be protected by insulation or
refractory materials or both.
    (C) Interlock switches shall be used on all hinged access doors,
sliding panels, or other such means of access to the applicator, unless
the applicator is an induction heating coil at dc ground potential or
operating at less than 150 volts ac.
    (D) Interlock switches shall be connected in such a manner as to
remove all power from the applicator when any one of the access doors
or panels is open.
    (vi) A readily accessible disconnecting means shall be provided by
which each heating equipment can be isolated from its supply circuit.
The ampere rating of this disconnecting means may not be less than the
nameplate current rating of the equipment. The supply circuit
disconnecting means is permitted as a heating equipment disconnecting
means where the circuit supplies only one piece of equipment.
    (2) Remote control. (i) If remote controls are used for applying
power, a selector switch shall be provided and interlocked to provide
power from only one control point at a time.
    (ii) Switches operated by foot pressure shall be provided with a
shield over the contact button to avoid accidental closing of the
switch.
    (h) Electrolytic cells. This paragraph applies to the installation
of the electrical components and accessory equipment of electrolytic
cells, electrolytic cell lines, and process power supply for the
production of aluminum, cadmium, chlorine, copper, fluorine, hydrogen
peroxide, magnesium, sodium, sodium chlorate, and zinc. Cells used as a
source of electric energy and for electroplating processes and cells
used for production of hydrogen are not covered by this paragraph.
    (1) Application. Installations covered by paragraph (h) of this
section shall comply with all applicable provisions of this subpart,
except as follows:
    (i) Overcurrent protection of electrolytic cell dc process power
circuits need not comply with the requirements of Sec.  1910.304(f);
    (ii) Equipment located or used within the cell line working zone or
associated with the cell line dc power circuits need not comply with
the provisions of Sec.  1910.304(g); and
    (iii) Electrolytic cells, cell line conductors, cell line
attachments, and the wiring of auxiliary equipment and devices within
the cell line working zone need not comply with the provisions of Sec.
1910.303 or Sec.  1910.304(b) and (c).
    (2) Disconnecting means. If more than one dc cell line process
power supply serves the same cell line, a disconnecting means shall be
provided on the cell line circuit side of each power supply to
disconnect it from the cell line circuit. Removable links or removable
conductors may be used as the disconnecting means.
    (3) Portable electric equipment. (i) The frames and enclosures of
portable electric equipment used within the cell line working zone may
not be grounded, unless the cell line circuit voltage does not exceed
200 volts DC or the frames are guarded.
    (ii) Ungrounded portable electric equipment shall be distinctively
marked and shall employ plugs and receptacles of a configuration that
prevents connection of this equipment to grounding receptacles and that
prevents inadvertent interchange of ungrounded

and grounded portable electric equipment.
    (4) Power supply circuits and receptacles for portable electric
equipment. (i) Circuits supplying power to ungrounded receptacles for
hand-held, cord- and plug-connected equipment shall meet the following
requirements:
    (A) The circuits shall be electrically isolated from any
distribution system supplying areas other than the cell line working
zone and shall be ungrounded;
    (B) The circuits shall be supplied through isolating transformers
with primaries operating at not more than 600 volts between conductors
and protected with proper overcurrent protection;
    (C) The secondary voltage of the isolating transformers may not
exceed 300 volts between conductors; and
    (D) All circuits supplied from the secondaries shall be ungrounded
and shall have an approved overcurrent device of proper rating in each
conductor.
    (ii) Receptacles and their mating plugs for ungrounded equipment
may not have provision for a grounding conductor and shall be of a
configuration that prevents their use for equipment required to be
grounded.
    (iii) Receptacles on circuits supplied by an isolating transformer
with an ungrounded secondary:
    (A) Shall have a distinctive configuration;
    (B) Shall be distinctively marked; and
    (C) May not be used in any other location in the facility.
    (5) Fixed and portable electric equipment. (i) The following need
not be grounded:
    (A) AC systems supplying fixed and portable electric equipment
within the cell line working zone; and
    (B) Exposed conductive surfaces, such as electric equipment
housings, cabinets, boxes, motors, raceways and the like that are
within the cell line working zone.
    (ii) Auxiliary electric equipment, such as motors, transducers,
sensors, control devices, and alarms, mounted on an electrolytic cell
or other energized surface shall be connected to the premises wiring
systems by any of the following means:
    (A) Multiconductor hard usage or extra hard usage flexible cord;
    (B) Wire or cable in suitable nonmetallic raceways or cable trays;
or
    (C) Wire or cable in suitable metal raceways or metal cable trays
installed with insulating breaks such that they will not cause a
potentially hazardous electrical condition.
    (iii) Fixed electric equipment may be bonded to the energized
conductive surfaces of the cell line, its attachments, or auxiliaries.
If fixed electric equipment is mounted on an energized conductive
surface, it shall be bonded to that surface.
    (6) Auxiliary nonelectrical connections. Auxiliary nonelectrical
connections such as air hoses, water hoses, and the like, to an
electrolytic cell, its attachments, or auxiliary equipment may not have
continuous conductive reinforcing wire, armor, braids, or the like.
Hoses shall be of a nonconductive material.
    (7) Cranes and hoists. (i) The conductive surfaces of cranes and
hoists that enter the cell line working zone need not be grounded. The
portion of an overhead crane or hoist that contacts an energized
electrolytic cell or energized attachments shall be insulated from
ground.
    (ii) Remote crane or hoist controls that may introduce hazardous
electrical conditions into the cell line working zone shall employ one
or more of the following systems:
    (A) Isolated and ungrounded control circuit;
    (B) Nonconductive rope operator;
    (C) Pendant pushbutton with nonconductive supporting means and with
nonconductive surfaces or ungrounded exposed conductive surfaces; or
    (D) Radio.
    (i) Electrically driven or controlled irrigation machines--(1)
Lightning protection. If an irrigation machine has a stationary point,
a grounding electrode system shall be connected to the machine at the
stationary point for lightning protection.
    (2) Disconnecting means. (i) The main disconnecting means for a
center pivot irrigation machine shall be located at the point of
connection of electrical power to the machine or shall be visible and
not more than 15.2 m (50 ft) from the machine.
    (ii) The disconnecting means shall be readily accessible and
capable of being locked in the open position.
    (iii) A disconnecting means shall be provided for each motor and
controller.
    (j) Swimming pools, fountains, and similar installations. This
paragraph applies to electric wiring for and equipment in or adjacent
to all swimming, wading, therapeutic, and decorative pools and
fountains; hydro-massage bathtubs, whether permanently installed or
storable; and metallic auxiliary equipment, such as pumps, filters, and
similar equipment. Therapeutic pools in health care facilities are
exempt from these provisions.
    (1) Receptacles. (i) A single receptacle of the locking and
grounding type that provides power for a permanently installed swimming
pool recirculating pump motor may be located not less than 1.52 m (5
ft) from the inside walls of a pool. All other receptacles on the
property shall be located at least 3.05 m (10 ft) from the inside walls
of a pool.
    (ii) Receptacles that are located within 4.57 m (15 ft), or 6.08 m
(20 ft) if the installation was built after August 13, 2007, of the
inside walls of the pool shall be protected by ground-fault circuit
interrupters.
    (iii) Where a pool is installed permanently at a dwelling unit, at
least one 125-volt, 15- or 20-ampere receptacle on a general-purpose
branch circuit shall be located a minimum of 3.05 m (10 ft) and not
more than 6.08 m (20 ft) from the inside wall of the pool. This
receptacle shall be located not more than 1.98 m (6.5 ft) above the
floor, platform, or grade level serving the pool.

    Note to paragraph (j)(1) of this section: In determining these
dimensions, the distance to be measured is the shortest path the
supply cord of an appliance connected to the receptacle would follow
without piercing a floor, wall, or ceiling of a building or other
effective permanent barrier.

    (2) Lighting fixtures, lighting outlets, and ceiling suspended
(paddle) fans. (i) In outdoor pool areas, lighting fixtures, lighting
outlets, and ceiling-suspended (paddle) fans may not be installed over
the pool or over the area extending 1.52 m (5 ft) horizontally from the
inside walls of a pool unless no part of the lighting fixture of a
ceiling-suspended (paddle) fan is less than 3.66 m (12 ft) above the
maximum water level. However, a lighting fixture or lighting outlet
that was installed before April 16, 1981, may be located less than 1.52
m (5 ft) measured horizontally from the inside walls of a pool if it is
at least 1.52 m (5 ft) above the surface of the maximum water level and
is rigidly attached to the existing structure. It shall also be
protected by a ground-fault circuit interrupter installed in the branch
circuit supplying the fixture.
    (ii) Lighting fixtures and lighting outlets installed in the area
extending between 1.52 m (5 ft) and 3.05 m (10 ft) horizontally from
the inside walls of a pool shall be protected by a ground-fault circuit
interrupter unless installed 1.52 m (5 ft) above the maximum water
level and rigidly attached to the structure adjacent to or enclosing
the pool.
    (3) Cord- and plug-connected equipment. Flexible cords used with
the following equipment may not exceed 0.9 m (3 ft) in length and shall
have a

copper equipment grounding conductor with a grounding-type attachment
plug:
    (i) Cord- and plug-connected lighting fixtures installed within
4.88 m (16 ft) of the water surface of permanently installed pools; and
    (ii) Other cord- and plug-connected, fixed or stationary equipment
used with permanently installed pools.
    (4) Underwater equipment. (i) A ground-fault circuit interrupter
shall be installed in the branch circuit supplying underwater fixtures
operating at more than 15 volts. Equipment installed underwater shall
be identified for the purpose.
    (ii) No underwater lighting fixtures may be installed for operation
at over 150 volts between conductors.
    (iii) A lighting fixture facing upward shall have the lens
adequately guarded to prevent contact by any person.
    (5) Fountains. All electric equipment, including power supply
cords, operating at more than 15 volts and used with fountains shall be
protected by ground-fault circuit interrupters.
    (k) Carnivals, circuses, fairs, and similar events. This paragraph
covers the installation of portable wiring and equipment, including
wiring in or on all structures, for carnivals, circuses, exhibitions,
fairs, traveling attractions, and similar events.
    (1) Protection of electric equipment. Electric equipment and wiring
methods in or on rides, concessions, or other units shall be provided
with mechanical protection where such equipment or wiring methods are
subject to physical damage.
    (2) Installation. (i) Services shall be installed in accordance
with applicable requirements of this subpart, and, in addition, shall
comply with the following:
    (A) Service equipment may not be installed in a location that is
accessible to unqualified persons, unless the equipment is lockable;
and
    (B) Service equipment shall be mounted on solid backing and
installed so as to be protected from the weather, unless the equipment
is of weatherproof construction.
    (ii) Amusement rides and amusement attractions shall be maintained
not less than 4.57 m (15 ft) in any direction from overhead conductors
operating at 600 volts or less, except for the conductors supplying the
amusement ride or attraction. Amusement rides or attractions may not be
located under or within 4.57 m (15 ft) horizontally of conductors
operating in excess of 600 volts.
    (iii) Flexible cords and cables shall be listed for extra-hard
usage. When used outdoors, flexible cords and cables shall also be
listed for wet locations and shall be sunlight resistant.
    (iv) Single conductor cable shall be size No. 2 or larger.
    (v) Open conductors are prohibited except as part of a listed
assembly or festoon lighting installed in accordance with Sec.
1910.304(c).
    (vi) Flexible cords and cables shall be continuous without splice
or tap between boxes or fittings. Cord connectors may not be laid on
the ground unless listed for wet locations. Connectors and cable
connections may not be placed in audience traffic paths or within areas
accessible to the public unless guarded.
    (vii) Wiring for an amusement ride, attraction, tent, or similar
structure may not be supported by another ride or structure unless
specifically identified for the purpose.
    (viii) Flexible cords and cables run on the ground, where
accessible to the public, shall be covered with approved nonconductive
mats. Cables and mats shall be arranged so as not to present a tripping
hazard.
    (ix) A box or fitting shall be installed at each connection point,
outlet, switch point, or junction point.
    (3) Inside tents and concessions. Electrical wiring for temporary
lighting, where installed inside of tents and concessions, shall be
securely installed, and, where subject to physical damage, shall be
provided with mechanical protection. All temporary lamps for general
illumination shall be protected from accidental breakage by a suitable
fixture or lampholder with a guard.
    (4) Portable distribution and termination boxes. Employers may only
use portable distribution and termination boxes that meet the following
requirements:
    (i) Boxes shall be designed so that no live parts are exposed to
accidental contact. Where installed outdoors, the box shall be of
weatherproof construction and mounted so that the bottom of the
enclosure is not less than 152 mm (6 in.) above the ground;
    (ii) Busbars shall have an ampere rating not less than the
overcurrent device supplying the feeder supplying the box. Busbar
connectors shall be provided where conductors terminate directly on
busbars;
    (iii) Receptacles shall have overcurrent protection installed
within the box. The overcurrent protection may not exceed the ampere
rating of the receptacle, except as permitted in Sec.  1910.305(j)(4)
for motor loads;
    (iv) Where single-pole connectors are used, they shall comply with
the following:
    (A) Where ac single-pole portable cable connectors are used, they
shall be listed and of the locking type. Where paralleled sets of
current-carrying single-pole separable connectors are provided as input
devices, they shall be prominently labeled with a warning indicating
the presence of internal parallel connections. The use of single-pole
separable connectors shall comply with at least one of the following
conditions:
    (1) Connection and disconnection of connectors are only possible
where the supply connectors are interlocked to the source and it is not
possible to connect or disconnect connectors when the supply is
energized; or
    (2) Line connectors are of the listed sequential-interlocking type