Chapter 3 Wiring Methods and Materials

ARTICLE 392 -
CABLE TRAYS
392.8
(H) Exposed and Accessible. Cable trays shall be exposed
and accessible except as permitted by 392.6(G).
(I) Adequate Access. Sufficient space shall be provided
and maintained about cable trays to permit adequate access
for installing and maintaining the cables.
(J) Raceways, Cables, Boxes, and Conduit Bodies Supported
from Cable Tray Systems. In industrial facilities
where conditions of maintenance and supervision ensure
that only qualified persons service the installation and
where the cable tray systems are designed and installed to
support the load, such systems shall be permitted to support
raceways and cables, and boxes and conduit bodies covered
in 314.1. For raceways terminating at the tray, a listed cable
tray clamp or adapter shall be used to securely fasten the
raceway to the cable tray system. Additional supporting and
securing of the raceway shall be in accordance with the
requirements of the appropriate raceway article.
For raceways or cables running parallel to and attached
to the bottom or side of a cable tray system, fastening and
supporting shall be in accordance with the requirements of
the appropriate raceway or cable article.
For boxes and conduit bodies attached to the bottom or
side of a cable tray system, fastening and supporting shall
be in accordance with the requirements of 314.23.
392.7 Grounding.
(A) Metallic Cable Trays. Metallic cable trays that support
electrical conductors shall be grounded as required for
conductor enclosures in accordance with 250.96 and ~
(B) Steel or Aluminum Cable Tray Systems. Steel or
aluminum cable tray systems shall be permitted to be used
as equipment grounding conductors, provided all the following
requirements are met:
(1) The cable tray sections and fittings ~ identified ~':g
~~~nt grounding W.',~{jf.
(2) The minimum cross-sectional area of cable trays conform
to the requirements in Table 392.7(B).
(3) All cable tray sections and fittings ~ legibly and durably
marked to show the cross-sectional area of metal
in channel cable trays, or cable trays of one-piece construction,
and Ithe total cross-sectional area of both side
rails for ladder or trough cable trays.
(4) Cable tray sections, fittings, and connected raceways
~ bonded in accordance with 250.96, using bolted
mechanical connectors or bonding jumpers sized and
installed in accordance with 250.102.
392.8 Cable Insuallation.
(A) Cable Splices. Cable splices made and insulated by
approved methods shall be permitted to be located within a
Table 392.7(B) Metal Area Requirements for Cable Trays
Used as Equipment Grounding Conductor
Maximum Fuse
Ampere Rating, Minimum Cl'Oss-Sectional
Circuit Breaker
Ampere Trip Setting,
Area of Metal B
_
or Circuit Breaker
Protective Relay
Ampere Trip Setting
Aluminum
for Ground-Fault Steel Cable Trays Cable Trays
Protection of Any
Cable Circuit in the
Cable Tray System mm 2 in. 2 mm 2 in. 2
60 129 0.20 129 0.20
100 258 0.40 129 0.20
200 451.5 0.70 129 0.20
400 645 1.00 258 0.40
600 967.5 l.50 b 258 0.40
1000 387 0.60
1200 645 1.00
1600 967.5 1.50
2000 1290 2.oo b
"Total cross-sectional area of both side rails for ladder or trough cable
trays; or the minimum cross-sectional area of metal in channel cable
trays or cable trays of one-piece construction.
bSteel cable trays shall not be used as equipment grounding conduc­
tors for circuits with ground-fault protection above 600 amperes. Alu­
minum cable trays shall not be used as equipmtmt grounding conduc­
tors for circuits with ground-fault protection above 2000 amperes.
cable tray, provided they are accessible.
(B) Fastened Securely. In other than horizontal runs, the
cables shall be fastened securely to transverse members of
the cable trays.
(C) Bushed Conduit and Thbing. A box shall not be required
where cables or conductors are installed in bushed
conduit and tubing used for support or for protection
against physical damage.
(D) Connected in Parallel. Where singIe conductor cables
comprising each phase, neutral, or grounded conductor of n
alternating-current circuit are connected in parallel as permitted
in 310.4, the conductors shall be installed in groups consisting
of not more than one conductor pt:r phase, neutral, or
grounded conductor to prevent current imbalance in the paralleled
conductors due to inductive reactance.
Single conductors shall be securely bound in circuit
groups to prevent excessive movement due to fault-current
magnetic forces unless single conductors are cabled together,
such as triplexed assemblies.
(E) Single Conductors. Where any of the single conductors
installed in ladder or ventilated trough cable trays are 1/0
through 4/0 AWG, all single conductors shall be installed in a
2008 Edition NATIONAL ELECTRICAL CODE
76-231