Article 392 Cable Trays

This article covers cable tray systems, including ladder, ventilated trough, ventilated channel, solid bottom, and other similar structures.

The definition in this section shall apply within this article and throughout the Code.

Cable tray shall be permitted to be used as a support system for wiring methods containing service conductors, feeders, branch circuits, communications circuits, control circuits, and signaling circuits. Single insulated conductors shall be permitted in cable tray only when installed in accordance with 392.10(B)(1). Cable tray installations shall not be limited to industrial establishments. Where exposed to direct rays of the sun, insulated conductors and jacketed cables shall be identified as being sunlight resistant. Cable trays and their associated fittings shall be identified for the intended use.

The wiring methods in Table 392.10(A) shall be permitted to be installed in cable tray systems under the conditions described in their respective articles and sections.

Wiring Method	Article
Armored cable: Type AC	320
CATV cables	820
Class 2 and Class 3 cables	725
Communications cables	800
Communications raceways	725, 770, and 800
Electrical metallic tubing: Type EMT	358
Electrical nonmetallic tubing: Type ENT	362
Fire alarm cables	760
Flexible metal conduit: Type FMC	348
Flexible metallic tubing: Type FMT	360
Instrumentation tray cable: Type ITC	727
Intermediate metal conduit: Type IMC	342
Liquidtight flexible metal conduit: Type LFMC	350
Liquidtight flexible nonmetallic conduit: Type LFNC	356
Metal-clad cable: Type MC	330
Mineral-insulated, metal-sheathed cable: Type MI	332
Network-powered broadband communications cables	830
Nonmetallic-sheathed cable: Types NM, NMC, and NMS	334
Non—power-limited fire alarm cable	760
Optical fiber cables	770
Other factory-assembled, multiconductor control, signal, or power cables that are specifically approved for installation in cable trays
Power and control tray cable: Type TC	336
Power-limited fire alarm cable	760
Power-limited tray cable	725
Rigid metal conduit: Type RMC	344
Rigid polyvinyl chloride conduit: Type PVC	352
Reinforced thermosetting resin conduit: Type RTRC	355
Service-entrance cable: Types SE and USE	338
Underground feeder and branch-circuit cable: Type UF	340

The wiring methods in Table 392.10(A) shall be permitted to be used in any industrial establishment under the conditions described in their respective articles. In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified persons service the installed cable tray system, any of the cables in 392.10(B)(1) and (B)(2) shall be permitted to be installed in ladder, ventilated trough, solid bottom, or ventilated channel cable trays.

Cable trays in hazardous (classified) locations shall contain only the cable types and raceways permitted by other articles in this Code.

In addition to the uses permitted elsewhere in 392.10, nonmetallic cable tray shall be permitted in corrosive areas and in areas requiring voltage isolation.

In airports where maintenance and supervision conditions ensure that only qualified persons can access, install, or service the cable, airfield lighting cable used in series circuits that are rated up to 5000 volts and are powered by constant current regulators shall be permitted to be installed in cable trays.

Cable tray systems shall not be used in hoistways or where subject to severe physical damage.

Cable trays shall be installed as a complete system. Field bends or modifications shall be so made that the electrical continuity of the cable tray system and support for the cables is maintained. Cable tray systems shall be permitted to have mechanically discontinuous segments between cable tray runs or between cable tray runs and equipment.

Each run of cable tray shall be completed before the installation of cables.

In portions of runs where additional protection is required, covers or enclosures providing the required protection shall be of a material that is compatible with the cable tray.

Cable trays shall be permitted to extend transversely through partitions and walls or vertically through platforms and floors in wet or dry locations where the installations, complete with installed cables, are made in accordance with the requirements of 300.21.

Cable trays shall be exposed and accessible, except as permitted by 392.18(D).

Sufficient space shall be provided and maintained about cable trays to permit adequate access for installing and maintaining the cables.

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.

Cable trays containing conductors operating over 600 volts shall have a permanent, legible warning notice carrying the wording "DANGER — HIGH VOLTAGE — KEEP AWAY" placed in a readily visible position on all cable trays, with the spacing of warning notices not to exceed 3 m (10 ft). The danger marking(s) or labels shall comply with 110.21(B).

Multiconductor cables operating at 1000 volts or less shall be permitted to be installed in the same tray.

Cables operating at over 1000 volts and those operating at 1000 volts or less installed in the same cable tray shall comply with either of the following:

1. The cables operating at over 1000 volts are Type MC.
2. The cables operating at over 1000 volts are separated from the cables operating at 1000 volts or less by a solid fixed barrier of a material compatible with the cable tray.

Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), 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.

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.

The number of multiconductor cables, rated 2000 volts or less, permitted in a single cable tray shall not exceed the requirements of this section. The conductor sizes shall apply to both aluminum and copper conductors. Where dividers are used, fill calculations shall apply to each divided section of the cable tray.

Inside Width of Cable Tray		Maximum Allowable Fill Area for Multiconductor Cables
		Ladder or Ventilated Trough or Wire Mesh Cable Trays, 392.22(A)(1)				Solid Bottom Cable Trays, 392.22(A)(3)
		Column 1 Applicable for 392.22(A)(1)(b) Only		Column 2a Applicable for 392.22(A)(1)(c) Only		Column 3 Applicable for 392.22(A)(3)(b) Only		Column 4a Applicable for 392.22(A)(3)(c) Only
mm	in.	mm2	in.2	mm2	in.2	mm2	in.2	mm2	in.2
50	2.0	1,500	2.5	1,500 — (30 Sd)b	2.5 — (1.2 Sd)b	1,200	2.0	1,200 — (25 Sd)b	2.0 — Sdb
100	4.0	3,000	4.5	3,000 — (30 Sd)b	4.5 — (1.2 Sd)	2,300	3.5	2,300 — (25 Sd)	3.5 — Sd
150	6.0	4,500	7.0	4,500 — (30 Sd)b	7 — (1.2 Sd)	3,500	5.5	3,500 — (25 Sd)b	5.5—Sd
200	8.0	6,000	9.5	6,000 — (30 Sd)b	9.5 — (1.2 Sd)	4,500	7.0	4,500 — (25 Sd)	7.0 — Sd
225	9.0	6,800	10.5	6,800 — (30 Sd)	10.5 — (1.2 Sd)	5,100	8.0	5,100 — (25 Sd)	8.0 — Sd
300	12.0	9,000	14.0	9,000 — (30 Sd)	14 — (1.2 Sd)	7,100	11.0	7,100 — (25 Sd)	11.0 — Sd
400	16.0	12,000	18.5	12,000 — (30 Sd)	18.5 — (1.2 Sd)	9,400	14.5	9,400 — (25 Sd)	14.5 — Sd
450	18.0	13,500	21.0	13,500 — (30 Sd)	21 — (1.2 Sd)	10,600	16.5	10,600 — (25 Sd)	16.5 — Sd
500	20.0	15,000	23.5	15,000 — (30 Sd)	23.5 — (1.2 Sd)	11,800	18.5	11,800 — (25 Sd)	18.5 — Sd
600	24.0	18,000	28.0	18,000 — (30 Sd)	28 — (1.2 Sd)	14,200	22.0	14,200 — (25 Sd)	22.0 — Sd
750	30.0	22,500	35.0	22,500 — (30 Sd)	35 — (1.2 Sd)	17,700	27.5	17,700 — (25 Sd)	27.5 — Sd
900	36.0	27,000	42.0	27,000 — (30 Sd)	42 — (1.2 Sd)	21,300	33.0	21,300 — (25 Sd)	33.0 — Sd
aThe maximum allowable fill areas in Columns 2 and 4 shall be calculated. For example, the maximum allowable fill in mm2 for a 150-mm wide cable tray in Column 2 shall be 4500 minus (30 multiplied by Sd) [the maximum allowable fill, in square inches, for a 6-in. wide cable tray in Column 2 shall be 7 minus (1.2 multiplied by Sd)].
bThe term Sd in Columns 2 and 4 is equal to the sum of the diameters, in mm, of all cables 107.2 mm (in inches, of all 4/0 AWG) and larger multiconductor cables in the same cable tray with smaller cables.