[Code of Federal Regulations]
[Title 29, Volume 8]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 29CFR1926.403]
[Page 244-247]
TITLE 29--LABOR
CHAPTER XVII--OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT
OF LABOR
PART 1926_SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION--Table of Contents
Subpart K_Electrical
Sec. 1926.403 General requirements.
(a) Approval. All electrical conductors and equipment shall be
approved.
(b) Examination, installation, and use of equipment--(1)
Examination. The employer shall ensure that electrical equipment is free
from recognized hazards that are likely to cause death or serious
physical harm to employees. Safety of equipment shall be determined on
the basis of the following considerations:
(i) Suitability for installation and use in conformity with the
provisions of this subpart. Suitability of equipment for an identified
purpose may be evidenced by listing, labeling, or certification for that
identified purpose.
(ii) Mechanical strength and durability, including, for parts
designed to enclose and protect other equipment, the adequacy of the
protection thus provided.
(iii) Electrical insulation.
(iv) Heating effects under conditions of use.
(v) Arcing effects.
(vi) Classification by type, size, voltage, current capacity,
specific use.
(vii) Other factors which contribute to the practical safeguarding
of employees using or likely to come in contact with the equipment.
(2) Installation and use. Listed, labeled, or certified equipment
shall be installed and used in accordance with instructions included in
the listing, labeling, or certification.
(c) Interrupting rating. Equipment intended to break current shall
have an interrupting rating at system voltage sufficient for the current
that must be interrupted.
(d) Mounting and cooling of equipment--(1) Mounting. Electric
equipment
[[Page 245]]
shall be firmly secured to the surface on which it is mounted. Wooden
plugs driven into holes in masonry, concrete, plaster, or similar
materials shall not be used.
(2) Cooling. Electrical equipment which depends upon the natural
circulation of air and convection principles for cooling of exposed
surfaces shall be installed so that room air flow over such surfaces is
not prevented by walls or by adjacent installed equipment. For equipment
designed for floor mounting, clearance between top surfaces and adjacent
surfaces shall be provided to dissipate rising warm air. Electrical
equipment provided with ventilating openings shall be installed so that
walls or other obstructions do not prevent the free circulation of air
through the equipment.
(e) Splices. Conductors shall be spliced or joined with splicing
devices designed for the use or by brazing, welding, or soldering with a
fusible metal or alloy. Soldered splices shall first be so spliced or
joined as to be mechanically and electrically secure without solder and
then soldered. All splices and joints and the free ends of conductors
shall be covered with an insulation equivalent to that of the conductors
or with an insulating device designed for the purpose.
(f) Arcing parts. Parts of electric equipment which in ordinary
operation produce arcs, sparks, flames, or molten metal shall be
enclosed or separated and isolated from all combustible material.
(g) Marking. Electrical equipment shall not be used unless the
manufacturer's name, trademark, or other descriptive marking by which
the organization responsible for the product may be identified is placed
on the equipment and unless other markings are provided giving voltage,
current, wattage, or other ratings as necessary. The marking shall be of
sufficient durability to withstand the environment involved.
(h) Identification of disconnecting means and circuits. Each
disconnecting means required by this subpart for motors and appliances
shall be legibly marked to indicate its purpose, unless located and
arranged so the purpose is evident. Each service, feeder, and branch
circuit, at its disconnecting means or overcurrent device, shall be
legibly marked to indicate its purpose, unless located and arranged so
the purpose is evident. These markings shall be of sufficient durability
to withstand the environment involved.
(i) 600 Volts, nominal, or less. This paragraph applies to equipment
operating at 600 volts, nominal, or less.
(1) Working space about electric equipment. Sufficient access and
working space shall be provided and maintained about all electric
equipment to permit ready and safe operation and maintenance of such
equipment.
(i) Working clearances. Except as required or permitted elsewhere in
this subpart, the dimension of the working space in the direction of
access to live parts operating at 600 volts or less and likely to
require examination, adjustment, servicing, or maintenance while alive
shall not be less than indicated in Table K-1. In addition to the
dimensions shown in Table K-1, workspace shall not be less than 30
inches (762 mm) wide in front of the electric equipment. Distances shall
be measured from the live parts if they are exposed, or from the
enclosure front or opening if the live parts are enclosed. Walls
constructed of concrete, brick, or tile are considered to be grounded.
Working space is not required in back of assemblies such as dead-front
switchboards or motor control centers where there are no renewable or
adjustable parts such as fuses or switches on the back and where all
connections are accessible from locations other than the back.
Table K-1--Working Clearances
------------------------------------------------------------------------
Minimum clear distance
for conditions\1\
Nominal voltage to ground --------------------------
(a) (b) (c)
------------------------------------------------------------------------
Feet\2\ Feet\2\ Feet\2\
0-150........................................ 3 3 3
151-600...................................... 3 3\1/2\ 4
------------------------------------------------------------------------
\1\ Conditions (a), (b), and (c) are as follows: (a) Exposed live parts
on one side and no live or grounded parts on the other side of the
working space, or exposed live parts on both sides effectively guarded
by insulating material. Insulated wire or insulated busbars operating
at not over 300 volts are not considered live parts. (b) Exposed live
parts on one side and grounded parts on the other side. (c) Exposed
live parts on both sides of the workspace [not guarded as provided in
Condition (a)] with the operator between.
\2\ Note: For International System of Units (SI): one foot=0.3048m.
[[Page 246]]
(ii) Clear spaces. Working space required by this subpart shall not
be used for storage. When normally enclosed live parts are exposed for
inspection or servicing, the working space, if in a passageway or
general open space, shall be guarded.
(iii) Access and entrance to working space. At least one entrance
shall be provided to give access to the working space about electric
equipment.
(iv) Front working space. Where there are live parts normally
exposed on the front of switchboards or motor control centers, the
working space in front of such equipment shall not be less than 3 feet
(914 mm).
(v) Headroom. The minimum headroom of working spaces about service
equipment, switchboards, panelboards, or motor control centers shall be
6 feet 3 inches (1.91 m).
(2) Guarding of live parts. (i) Except as required or permitted
elsewhere in this subpart, live parts of electric equipment operating at
50 volts or more shall be guarded against accidental contact by cabinets
or other forms of enclosures, or by any of the following means:
(A) By location in a room, vault, or similar enclosure that is
accessible only to qualified persons.
(B) By partitions or screens so arranged that only qualified persons
will have access to the space within reach of the live parts. Any
openings in such partitions or screens shall be so sized and located
that persons are not likely to come into accidental contact with the
live parts or to bring conducting objects into contact with them.
(C) By location on a balcony, gallery, or platform so elevated and
arranged as to exclude unqualified persons.
(D) By elevation of 8 feet (2.44 m) or more above the floor or other
working surface and so installed as to exclude unqualified persons.
(ii) In locations where electric equipment would be exposed to
physical damage, enclosures or guards shall be so arranged and of such
strength as to prevent such damage.
(iii) Entrances to rooms and other guarded locations containing
exposed live parts shall be marked with conspicuous warning signs
forbidding unqualified persons to enter.
(j) Over 600 volts, nominal--(1) General. Conductors and equipment
used on circuits exceeding 600 volts, nominal, shall comply with all
applicable provisions of paragraphs (a) through (g) of this section and
with the following provisions which supplement or modify those
requirements. The provisions of paragraphs (j)(2), (j)(3), and (j)(4) of
this section do not apply to equipment on the supply side of the service
conductors.
(2) Enclosure for electrical installations. Electrical installations
in a vault, room, closet or in an area surrounded by a wall, screen, or
fence, access to which is controlled by lock and key or other equivalent
means, are considered to be accessible to qualified persons only. A
wall, screen, or fence less than 8 feet (2.44 m) in height is not
considered adequate to prevent access unless it has other features that
provide a degree of isolation equivalent to an 8-foot (2.44-m) fence.
The entrances to all buildings, rooms or enclosures containing exposed
live parts or exposed conductors operating at over 600 volts, nominal,
shall be kept locked or shall be under the observation of a qualified
person at all times.
(i) Installations accessible to qualified persons only. Electrical
installations having exposed live parts shall be accessible to qualified
persons only and shall comply with the applicable provisions of
paragraph (j)(3) of this section.
(ii) Installations accessible to unqualified persons. Electrical
installations that are open to unqualified persons shall be made with
metal-enclosed equipment or shall be enclosed in a vault or in an area,
access to which is controlled by a lock. Metal-enclosed switchgear, unit
substations, transformers, pull boxes, connection boxes, and other
similar associated equipment shall be marked with appropriate caution
signs. If equipment is exposed to physical damage from vehicular
traffic, guards shall be provided to prevent such damage. Ventilating or
similar openings in metal-enclosed equipment shall be designed so that
foreign objects inserted through these openings will be deflected from
energized parts.
[[Page 247]]
(3) Workspace about equipment. Sufficient space shall be provided
and maintained about electric equipment to permit ready and safe
operation and maintenance of such equipment. Where energized parts are
exposed, the minimum clear workspace shall not be less than 6 feet 6
inches (1.98 m) high (measured vertically from the floor or platform),
or less than 3 feet (914 mm) wide (measured parallel to the equipment).
The depth shall be as required in Table K-2. The workspace shall be
adequate to permit at least a 90-degree opening of doors or hinged
panels.
(i) Working space. The minimum clear working space in front of
electric equipment such as switchboards, control panels, switches,
circuit breakers, motor controllers, relays, and similar equipment shall
not be less than specified in Table K-2 unless otherwise specified in
this subpart. Distances shall be measured from the live parts if they
are exposed, or from the enclosure front or opening if the live parts
are enclosed. However, working space is not required in back of
equipment such as deadfront switchboards or control assemblies where
there are no renewable or adjustable parts (such as fuses or switches)
on the back and where all connections are accessible from locations
other than the back. Where rear access is required to work on de-
energized parts on the back of enclosed equipment, a minimum working
space of 30 inches (762 mm) horizontally shall be provided.
Table K-2--Minimum Depth of Clear Working Space in Front of Electric
Equipment
------------------------------------------------------------------------
Conditions\1\
Nominal voltage to ground --------------------------
(a) (b) (c)
------------------------------------------------------------------------
Feet\2\ Feet\2\ Feet\2\
601 to 2,500................................. 3 4 5
2,501 to 9,000............................... 4 5 6
9,001 to 25,000.............................. 5 6 9
25,001 to 75 kV.............................. 6 8 10
Above 75kV................................... 8 10 12
------------------------------------------------------------------------
\1\Conditions (a), (b), and (c) are as follows: (a) Exposed live parts
on one side and no live or grounded parts on the other side of the
working space, or exposed live parts on both sides effectively guarded
by insulating materials. Insulated wire or insulated busbars operating
at not over 300 volts are not considered live parts. (b) Exposed live
parts on one side and grounded parts on the other side. Walls
constructed of concrete, brick, or tile are considered to be grounded
surfaces. (c) Exposed live parts on both sides of the workspace [not
guarded as provided in Condition (a)] with the operator between.
\2\ Note: For SI units: one foot=0.3048 m.
(ii) Lighting outlets and points of control. The lighting outlets
shall be so arranged that persons changing lamps or making repairs on
the lighting system will not be endangered by live parts or other
equipment. The points of control shall be so located that persons are
not likely to come in contact with any live part or moving part of the
equipment while turning on the lights.
(iii) Elevation of unguarded live parts. Unguarded live parts above
working space shall be maintained at elevations not less than specified
in Table K-3.
Table K-3--Elevation of Unguarded Energized Parts Above Working Space
------------------------------------------------------------------------
Nominal voltage between phases Minimum elevation
------------------------------------------------------------------------
601-7,500................................. 8 feet 6 inches.\1\
7,501-35,000.............................. 9 feet.
Over 35kV................................. 9 feet+0.37 inches per kV
above 35kV.
------------------------------------------------------------------------
\1\ Note: For SI units: one inch=25.4 mm; one foot=0.3048 m.
(4) Entrance and access to workspace. At least one entrance not less
than 24 inches (610 mm) wide and 6 feet 6 inches (1.98 m) high shall be
provided to give access to the working space about electric equipment.
On switchboard and control panels exceeding 48 inches (1.22 m) in width,
there shall be one entrance at each end of such board where practicable.
Where bare energized parts at any voltage or insulated energized parts
above 600 volts are located adjacent to such entrance, they shall be
guarded.
[51 FR 25318, July 11, 1986, as amended at 61 FR 5510, Feb. 13, 1996]
