[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: 29CFR1926.408]
[Page 261-263]
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. 1926.408 Special systems.
(a) Systems over 600 volts, nominal. Paragraphs (a)(1) through
(a)(4) of this section contain general requirements for all circuits and
equipment operated at over 600 volts.
(1) Wiring methods for fixed installations--(i) Above ground. Above-
ground conductors shall be installed in rigid metal conduit, in
intermediate metal conduit, in cable trays, in cablebus, in other
suitable raceways, or as open runs of metal-clad cable designed for the
use and purpose. However, open runs of non-metallic-sheathed cable or of
bare conductors or busbars may be installed in locations which are
accessible only to qualified persons. Metallic shielding components,
such as tapes, wires, or braids for conductors, shall be grounded. Open
runs of insulated wires and cables having a bare lead sheath or a
braided outer covering shall be supported in a manner designed to
prevent physical damage to the braid or sheath.
(ii) Installations emerging from the ground. Conductors emerging
from the ground shall be enclosed in raceways. Raceways installed on
poles shall be of rigid metal conduit, intermediate metal conduit, PVC
schedule 80 or equivalent extending from the ground line up to a point 8
feet (2.44 m) above finished grade. Conductors entering a building shall
be protected by an enclosure from the ground line to the point of
entrance. Metallic enclosures shall be grounded.
(2) Interrupting and isolating devices--(i) Circuit breakers.
Circuit breakers located indoors shall consist of metal-enclosed or
fire-resistant, cell-mounted units. In locations accessible only to
qualified personnel, open mounting of circuit breakers is permitted. A
means of indicating the open and closed position of circuit breakers
shall be provided.
(ii) Fused cutouts. Fused cutouts installed in buildings or
transformer vaults shall be of a type identified for the purpose. They
shall be readily accessible for fuse replacement.
(iii) Equipment isolating means. A means shall be provided to
completely isolate equipment for inspection and repairs. Isolating means
which are not designed to interrupt the load current of the circuit
shall be either
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interlocked with a circuit interrupter or provided with a sign warning
against opening them under load.
(3) Mobile and portable equipment--(i) Power cable connections to
mobile machines. A metallic enclosure shall be provided on the mobile
machine for enclosing the terminals of the power cable. The enclosure
shall include provisions for a solid connection for the ground wire(s)
terminal to ground effectively the machine frame. The method of cable
termination used shall prevent any strain or pull on the cable from
stressing the electrical connections. The enclosure shall have provision
for locking so only authorized qualified persons may open it and shall
be marked with a sign warning of the presence of energized parts.
(ii) Guarding live parts. All energized switching and control parts
shall be enclosed in effectively grounded metal cabinets or enclosures.
Circuit breakers and protective equipment shall have the operating means
projecting through the metal cabinet or enclosure so these units can be
reset without locked doors being opened. Enclosures and metal cabinets
shall be locked so that only authorized qualified persons have access
and shall be marked with a sign warning of the presence of energized
parts. Collector ring assemblies on revolving-type machines (shovels,
draglines, etc.) shall be guarded.
(4) Tunnel installations--(i) Application. The provisions of this
paragraph apply to installation and use of high-voltage power
distribution and utilization equipment which is associated with tunnels
and which is portable and/or mobile, such as substations, trailers,
cars, mobile shovels, draglines, hoists, drills, dredges, compressors,
pumps, conveyors, and underground excavators.
(ii) Conductors. Conductors in tunnels shall be installed in one or
more of the following:
(A) Metal conduit or other metal raceway,
(B) Type MC cable, or
(C) Other suitable multiconductor cable.
Conductors shall also be so located or guarded as to protect them from
physical damage. Multiconductor portable cable may supply mobile
equipment. An equipment grounding conductor shall be run with circuit
conductors inside the metal raceway or inside the multiconductor cable
jacket. The equipment grounding conductor may be insulated or bare.
(iii) Guarding live parts. Bare terminals of transformers, switches,
motor controllers, and other equipment shall be enclosed to prevent
accidental contact with energized parts. Enclosures for use in tunnels
shall be drip-proof, weatherproof, or submersible as required by the
environmental conditions.
(iv) Disconnecting means. A disconnecting means that simultaneously
opens all ungrounded conductors shall be installed at each transformer
or motor location.
(v) Grounding and bonding. All nonenergized metal parts of electric
equipment and metal raceways and cable sheaths shall be grounded and
bonded to all metal pipes and rails at the portal and at intervals not
exceeding 1000 feet (305 m) throughout the tunnel.
(b) Class 1, Class 2, and Class 3 remote control, signaling, and
power-limited circuits--(1) Classification. Class 1, Class 2, or Class 3
remote control, signaling, or power-limited circuits are characterized
by their usage and electrical power limitation which differentiates them
from light and power circuits. These circuits are classified in
accordance with their respective voltage and power limitations as
summarized in paragraphs (b)(1)(i) through (b)(1)(iii) of this section.
(i) Class 1 circuits--(A) A Class 1 power-limited circuit is
supplied from a source having a rated output of not more than 30 volts
and 1000 volt-amperes.
(B) A Class 1 remote control circuit or a Class 1 signaling circuit
has a voltage which does not exceed 600 volts; however, the power output
of the source need not be limited.
(ii) Class 2 and Class 3 circuits--(A) Power for Class 2 and Class 3
circuits is limited either inherently (in which no overcurrent
protection is required) or by a combination of a power source and
overcurrent protection.
(B) The maximum circuit voltage is 150 volts AC or DC for a Class 2
inherently limited power source, and 100
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volts AC or DC for a Class 3 inherently limited power source.
(C) The maximum circuit voltage is 30 volts AC and 60 volts DC for a
Class 2 power source limited by overcurrent protection, and 150 volts AC
or DC for a Class 3 power source limited by overcurrent protection.
(iii) Application. The maximum circuit voltages in paragraphs
(b)(1)(i) and (b)(1)(ii) of this section apply to sinusoidal AC or
continuous DC power sources, and where wet contact occurrence is not
likely.
(2) Marking. A Class 2 or Class 3 power supply unit shall not be
used unless it is durably marked where plainly visible to indicate the
class of supply and its electrical rating.
(c) Communications systems--(1) Scope. These provisions for
communication systems apply to such systems as central-station-connected
and non-central-station-connected telephone circuits, radio receiving
and transmitting equipment, and outside wiring for fire and burglar
alarm, and similar central station systems. These installations need not
comply with the provisions of Sec. Sec. 1926.403 through 1926.408(b),
except Sec. 1926.404(c)(1)(ii) and Sec. 1926.407.
(2) Protective devices--(i) Circuits exposed to power conductors.
Communication circuits so located as to be exposed to accidental contact
with light or power conductors operating at over 300 volts shall have
each circuit so exposed provided with an approved protector.
(ii) Antenna lead-ins. Each conductor of a lead-in from an outdoor
antenna shall be provided with an antenna discharge unit or other means
that will drain static charges from the antenna system.
(3) Conductor location--(i) Outside of buildings--(A) Receiving
distribution lead-in or aerial-drop cables attached to buildings and
lead-in conductors to radio transmitters shall be so installed as to
avoid the possibility of accidental contact with electric light or power
conductors.
(B) The clearance between lead-in conductors and any lightning
protection conductors shall not be less than 6 feet (1.83 m).
(ii) On poles. Where practicable, communication conductors on poles
shall be located below the light or power conductors. Communications
conductors shall not be attached to a crossarm that carries light or
power conductors.
(iii) Inside of buildings. Indoor antennas, lead-ins, and other
communication conductors attached as open conductors to the inside of
buildings shall be located at least 2 inches (50.8 mm) from conductors
of any light or power or Class 1 circuits unless a special and equally
protective method of conductor separation is employed.
(4) Equipment location. Outdoor metal structures supporting
antennas, as well as self-supporting antennas such as vertical rods or
dipole structures, shall be located as far away from overhead conductors
of electric light and power circuits of over 150 volts to ground as
necessary to avoid the possibility of the antenna or structure falling
into or making accidental contact with such circuits.
(5) Grounding--(i) Lead-in conductors. If exposed to contact with
electric light or power conductors, the metal sheath of aerial cables
entering buildings shall be grounded or shall be interrupted close to
the entrance to the building by an insulating joint or equivalent
device. Where protective devices are used, they shall be grounded.
(ii) Antenna structures. Masts and metal structures supporting
antennas shall be permanently and effectively grounded without splice or
connection in the grounding conductor.
(iii) Equipment enclosures. Transmitters shall be enclosed in a
metal frame or grill or separated from the operating space by a barrier,
all metallic parts of which are effectively connected to ground. All
external metal handles and controls accessible to the operating
personnel shall be effectively grounded. Unpowered equipment and
enclosures shall be considered grounded where connected to an attached
coaxial cable with an effectively grounded metallic shield.
[51 FR 25318, July 11, 1986, as amended at 61 FR 5510, Feb. 13, 1996]
[[Page 264]]
