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392.1 Scope
This article covers cable tray systems, including ladder, ventilated trough, ventilated channel, solid bottom, and other similar structures.
Informational Note: For further information on cable trays, see ANSI/NEMA-VE 1-2017, Metal Cable Tray Systems, and NECA/NEMA 105-2015, Standard for Installing Metal Cable Tray Systems.
392.2 Definition
The definition in this section shall apply within this article and throughout the Code.
Cable Tray System. A unit or assembly of units or sections and associated fittings forming a structural system used to securely fasten or support cables and raceways.
392.10 Uses Permitted
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.
(A) Wiring Methods
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.
Table 392.10(A) Wiring Methods
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
(B) In Industrial Establishments
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.
(1) Single-Conductor Cables
Single-conductor cables shall be permitted to be installed in accordance with (B)(1)(a) through (B)(1)(c).
(a) Single-conductor cables shall be 1/0 AWG or larger and shall be of a type listed and marked on the surface for use in cable trays. Where 1/0 AWG through 4/0 AWG single-conductor cables are installed in ladder cable tray, the maximum allowable rung spacing for the ladder cable tray shall be 225 mm (9 in.).
(b) Welding cables shall comply with Article 630, Part IV.
(c) Single conductors used as equipment grounding conductors shall be insulated, covered, or bare, and they shall be 4 AWG or larger.
(2) Single- And Multiconductor Medium Voltage Cables
Single- and multiconductor medium voltage cables shall be Type MV cable. Single conductors shall be installed in accordance with 392.10(B)(1).
(C) Hazardous (Classified) Locations
Cable trays in hazardous (classified) locations shall contain only the cable types and raceways permitted by other articles in this Code.
(D) Nonmetallic Cable Tray
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.
(E) Airfield Lighting Cable Tray
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.
Informational Note: Federal Aviation Administration (FAA) Advisory Circulars (ACs) provide additional practices and methods for airport lighting.
392.12 Uses Not Permitted
Cable tray systems shall not be used in hoistways or where subject to severe physical damage.
392.18 Cable Tray Installation
(A) Complete System
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.
(B) Completed Before Installation
Each run of cable tray shall be completed before the installation of cables.
(C) Covers
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.
(D) Through Partitions and Walls
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.
(E) Exposed and Accessible
Cable trays shall be exposed and accessible, except as permitted by 392.18(D).
(F) Adequate Access
Sufficient space shall be provided and maintained about cable trays to permit adequate access for installing and maintaining the cables.
(G) 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.
(H) Marking
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).
Exception: Where not accessible (as applied to equipment), in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation, cable tray system warning notices shall be located where necessary for the installation to ensure safe maintenance and operation.
392.20 Cable and Conductor Installation
(A) Multiconductor Cables Operating at 1000 Volts or Less
Multiconductor cables operating at 1000 volts or less shall be permitted to be installed in the same tray.
(B) Cables Operating at Over 1000 Volts
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.
(C) Connected in Parallel
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.
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.
(D) 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.
392.22 Number of Conductors or Cables
(A) Number of Multiconductor Cables, Rated 2000 Volts or Less, in Cable Trays
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.
Table 392.22(A) Allowable Cable Fill Area for Multiconductor Cables in Ladder, Ventilated Trough, or Solid Bottom Cable Trays for Cables Rated 2000 Volts or Less
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.
(1) Ladder or Ventilated Trough Cable Trays Containing 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 of cables shall conform to the following:
(a) Where all of the cables are 4/0 AWG or larger, the sum of the diameters of all cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Where the cable ampacity is determined according to 392.80(A)(1)(c), the cable tray width shall not be less than the sum of the diameters of the cables and the sum of the required spacing widths between the cables.
(b) Where all of the cables are smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables shall not exceed the maximum allowable cable fill area in Column 1 of Table 392.22(A) for the appropriate cable tray width.
(c) Where 4/0 AWG or larger cables are installed in the same cable tray with cables smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables smaller than 4/0 AWG shall not exceed the maximum allowable fill area resulting from the calculation in Column 2 of Table 392.22(A) for the appropriate cable tray width. The 4/0 AWG and larger cables shall be installed in a single layer, and no other cables shall be placed on them.
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