electrical conductors shall be grounded as required for conductor enclosures in accordance with 250.96 and Part IV of Article 250.

(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 are identified as an equipment grounding conductor.

(2) The minimum cross-sectional area of cable trays conform to the requirements in Table 392.7(B).

Ampere Trip SettingProtection of Any

Cable Circuit in the

Cable Tray System mm 2 in.2 mm2 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 1.50" 258 0.40

1000 — — 387 0.60

1200 — — 645 1.00

1600 — — 967.5 1.50

2000 — — 1290 2.00 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 conductors for circuits with ground-fault protection above 600 amperes. Aluminum cable trays shall not be used as equipment grounding conductors for circuits with ground-fault protection above 2000 amperes.

cable tray, provided they are accessible. Splices shall be permitted to project above the side rails where not subject to physical damage.

(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 Tubing. A box shall not be re- quired 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 single 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 per 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 single layer. Conductors that are bound together to comprise each circuit group shall be permitted to be installed in other than a single layer.

392.9 Number of Multiconductor Cables, Rated 2000
Volts or Less, in Cable Trays. The number of multicon-
ductor cables, rated 2000 volts or less, permitted in a
single cable tray shall not exceed the requirements of
this section. The conductor sizes herein apply to both
aluminum and copper conductors.
(A) Any Mixture of Cables. Where ladder or ventilated trough cable trays contain multiconductor power or lighting cables, or any mixture of multiconductor power, lighting, control, and signal cables, the maximum number