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Article 392

  1. Cable TraysPart I. General
    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 1-2009, Metal Cable Tray Systems; NECA/NEMA 105-2015, Standard for Installing Metal Cable Tray Systems; and NEMA–FG 1-1993, Nonmetallic Cable Tray Systems.
    2. Definition.
    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.
    Part II. Installation392.10 Uses Permitted. Cable tray shall be permitted to be used as a support system for service conductors, feeders, branch circuits, communications circuits, control circuits, and signaling circuits. 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 identi‐ fied as being sunlight resistant. Cable trays and their associated fittings shall be identified for the intended use.
    1. 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.
    2. 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 respec‐ tive 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 chan‐ nel cable trays.
      1. Single-conductor cables shall be permitted to be installed in accordance with (B)(1)(a) through (B)(1)(c).
        1. Single-conductor cable 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 maxi‐ mum allowable rung spacing for the ladder cable tray shall be 225 mm (9 in.).
        2. Welding cables shall comply with the provisions of Article 630, Part IV.
        3. 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 shall be Type MV cable. Single conductors shall be installed in accordance with 392.10(B)(1).

    Table 392.10(A) Wiring Methods
    392.18 Cable Tray Installation.Wiring MethodArticle(A) Complete System. Cable trays shall be installed as acomplete system. Field bends or modifications shall be so madeArmored cable: Type AC320that the electrical continuity of the cable tray system andCATV cables820support for the cables is maintained. Cable tray systems shall beClass 2 and Class 3 cables725permitted to have mechanically discontinuous segmentsCommunications cables800between cable tray runs or between cable tray runs and equip‐Communications raceways725, 770, and 800ment.Electrical metallic tubing: Type EMT Electrical nonmetallic tubing: Type ENT Fire alarm cables358362760(B) Completed Before Installation. Each run of cable tray shall be completed before the installation of cables.Flexible metal conduit: Type FMC348(C) Covers. In portions of runs where additional protection isFlexible metallic tubing: Type FMT360required, covers or enclosures providing the required protec‐Instrumentation tray cable: Type ITC727tion shall be of a material that is compatible with the cable tray.imageIntermediate metal conduit: Type IMC 342Liquidtight flexible metal conduit: Type LFMCLiquidtight flexible nonmetallic conduit: Type LFNC350356(D) Through Partitions and Walls. Cable trays shall be permit‐ ted to extend transversely through partitions and walls or verti‐ cally through platforms and floors in wet or dry locations where the installations, complete with installed cables, areMetal-clad cable: Type MC 330made in accordance with the requirements of 300.21.Mineral-insulated, metal-sheathed cable: Type MINetwork-powered broadband communications cablesNonmetallic-sheathed cable: Types NM, NMC, and NMS332
    830
    334
    1. Exposed and Accessible. Cable trays shall be exposed and accessible, except as permitted by 392.18(D).
    2. Adequate Access. Sufficient space shall be provided and maintained about cable trays to permit adequate access for installing and maintaining the cables.Non–power-limited fire alarm cable 760Optical fiber cables 770Power and control tray cable: Type TC336Power-limited fire alarm cable760Power-limited tray cable725Rigid metal conduit: Type RMC344Rigid polyvinyl chloride conduit: Type PVC352Reinforced thermosetting resin conduit:355Other factory-assembled, multiconductor control, signal, or power cables that are specifically approved for installation in cable trays
      Type RTRCService-entrance cable: Types SE and USE 338
    3. Raceways, Cables, Boxes, and Conduit Bodies Supported from Cable Tray Systems. In industrial facilities where condi‐ tions of maintenance and supervision ensure that only quali‐ fied 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 termi‐ nating 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 andUnderground feeder and branch-circuit cable: Type UF340supporting 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
  2. Hazardous (Classified) Locations. Cable trays in hazard‐ ous (classified) locations shall contain only the cable types and raceways permitted by other articles in this Code.
  3. 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.imageN
  4. Airfield Lighting Cable Tray. In airports where mainte‐ nance 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 meth‐ ods for airport lighting.

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

of a cable tray system, fastening and supporting shall be in accordance with the requirements of 314.23.

(H) Marking. Cable trays containing conductors rated over 600 volts shall have a permanent, legible warning notice carry‐ ing 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 installa‐ tion to ensure safe maintenance and operation.

392.20 Cable and Conductor Installation.

  1. 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.
  2. Cables Operating at Over 1000 Volts. Cables operating at over 1000 volts and those operating at 1000 volts or less instal‐ led in the same cable tray shall comply with either of the follow‐ ing:
    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.
  3. Connected in Parallel. Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permit‐ ted in 310.10(H), 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.
  4. 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.

  1. 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.
    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:
      1. 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.
      2. 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.
      3. 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.
    2. Ladder or Ventilated Trough Cable Trays Containing Multi‐ conductor Control and/or Signal Cables Only. Where a ladder or ventilated trough cable tray having a usable inside depth of 150 mm (6 in.) or less contains multiconductor control and/or signal cables only, the sum of the cross-sectional areas of all cables at any cross section shall not exceed 50 percent of the interior cross-sectional area of the cable tray. A depth of 150 mm (6 in.) shall be used to calculate the allowable interior cross-sectional area of any cable tray that has a usable inside depth of more than 150 mm (6 in.).
    3. Solid Bottom Cable Trays Containing Any Mixture of Cables. Where solid bottom cable trays contain multiconduc‐ tor 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:
      1. Where all of the cables are 4/0 AWG or larger, the sum of the diameters of all cables shall not exceed 90 percent of the cable tray width, and the cables shall be installed in a single layer.
      2. 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 3 of Table 392.22(A) for the appropriate cable tray width.
      3. 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 computation in Column 4 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.
    4. Solid Bottom Cable Tray Containing Multiconductor Control and/or Signal Cables Only. Where a solid bottom cable tray having a usable inside depth of 150 mm (6 in.) or less contains multiconductor control and/or signal cables only, the sum of the cross sectional areas of all cables at any cross section shall not exceed 40 percent of the interior cross- sectional area of the cable tray. A depth of 150 mm (6 in.) shall be used to calculate the allowable interior cross-sectional area of any cable tray that has a usable inside depth of more than 150 mm (6 in.).
    5. Ventilated Channel Cable Trays Containing Multiconductor Cables of Any Type. Where ventilated channel cable trays contain multiconductor cables of any type, the following shall apply:
      1. Where only one multiconductor cable is installed, the cross-sectional area shall not exceed the value specified in Column 1 of Table 392.22(A)(5).
      2. Where more than one multiconductor cable is instal‐ led, the sum of the cross-sectional area of all cables shall not exceed the value specified in Column 2 of Table 392.22(A)(5).
    6. Solid Channel Cable Trays Containing Multiconductor Cables of Any Type. Where solid channel cable trays contain multiconductor cables of any type, the following shall apply:
      1. Where only one multiconductor cable is installed, the cross-sectional area of the cable shall not exceed the value specified in Column 1 of Table 392.22(A)(6).
      2. Where more than one multiconductor cable is instal‐ led, the sum of the cross-sectional area of all cable shall not exceed the value specified in Column 2 of Table 392.22(A)(6).
  2. Number of Single-Conductor Cables, Rated 2000 Volts or Less, in Cable Trays. The number of single conductor cables, rated 2000 volts or less, permitted in a single cable tray sectionTable 392.22(A)(5) Allowable Cable Fill Area for Multiconductor Cables in Ventilated Channel Cable Trays for Cables Rated 2000 Volts or Lessshall not exceed the requirements of this section. The single                                                                                                                                conductors, or conductor assemblies, shall be evenly distrib‐ uted across the cable tray. The conductor sizes shall apply to both aluminum and copper conductors.Maximum Allowable Fill Area for Multiconductor CablesimageColumn 2
    1. Ladder or Ventilated Trough Cable Trays. Where ladder or ventilated trough cable trays contain single-conductorInside Width of Cable TrayColumn 1 One CableMore Than One Cablecables, the maximum number of single conductors shall
      imageimageimage  mm in. mm2 in.2 mm2 in.2conform to the following:                                                                                                                                
      1. Where all of the cables are 1000 kcmil or larger, the sum of the diameters of all single-conductor cables shall not exceed the cable tray width, and the cables 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.
      2. Where all of the cables are from 250 kcmil through 900 kcmil, the sum of the cross-sectional areas of all single-75 3 1500 2.3 850 1.3100 4 2900 4.5 1600 2.5150 6 4500 7.0 2450 3.8
        Table 392.22(A)(6) Allowable Cable Fill Area for Multiconductor Cables in Solid Channel Cable Trays for Cables Rated 2000 Volts or Lessconductor cables shall not exceed the maximum allowable                                                                                                                                cable fill area in Column 1 of Table 392.22(B)(1) for the appropriate cable tray width.mmin.
        mm2in.2
        mm2in.2502
        8501.3
        5000.8753
        13002.0
        7001.11004
        24003.7
        14002.11506
        36005.5
        21003.2
      3. Where 1000 kcmil or larger single-conductor cables are installed in the same cable tray with single-conductor cables smaller than 1000 kcmil, the sum of the cross sectional areas of all cables smaller than 1000 kcmil shall not exceed the maxi‐ mum allowable fill area resulting from the computation in Column 2 of Table 392.22(B)(1) for the appropriate cable tray width.
      4. Where any of the single conductor cables are 1/0 through 4/0 AWG, the sum of the diameters of all single conductor cables shall not exceed the cable tray width.Inside Width of Cable TrayColumn 1 One CableColumn 2 More Than One Cable
        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 TrayMaximum Allowable Fill Area for Multiconductor CablesLadder 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 2aApplicable 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)Onlymmin.mm2in.2mm2in.2mm2in.2mm2in.2502.01,5002.51,500 – (30 Sd)b2.5 – (1.2 Sd)b1,2002.01,200 – (25 Sd)b2.0 – Sdb1004.03,0004.53,000 – (30 Sd)b4.5 – (1.2 Sd)2,3003.52,300 – (25 Sd)3.5 – Sd1506.04,5007.04,500 – (30 Sd)b7 – (1.2 Sd)3,5005.53,500 – (25 Sd)b5.5–Sd2008.06,0009.56,000 – (30 Sd)b9.5 – (1.2 Sd)4,5007.04,500 – (25 Sd)7.0 – Sd2259.06,80010.56,800 – (30 Sd)10.5 – (1.2 Sd)5,1008.05,100 – (25 Sd)8.0 – Sd30012.09,00014.09,000 – (30 Sd)14 – (1.2 Sd)7,10011.07,100 – (25 Sd)11.0 – Sd40016.012,00018.512,000 – (30 Sd)18.5 – (1.2 Sd)9,40014.59,400 – (25 Sd)14.5 – Sd45018.013,50021.013,500 – (30 Sd)21 – (1.2 Sd)10,60016.510,600 – (25 Sd)16.5 – Sd50020.015,00023.515,000 – (30 Sd)23.5 – (1.2 Sd)11,80018.511,800 – (25 Sd)18.5 – Sd60024.018,00028.018,000 – (30 Sd)28 – (1.2 Sd)14,20022.014,200 – (25 Sd)22.0 – Sd75030.022,50035.022,500 – (30 Sd)35 – (1.2 Sd)17,70027.517,700 – (25 Sd)27.5 – Sd90036.027,00042.027,000 – (30 Sd)42 – (1.2 Sd)21,30033.021,300 – (25 Sd)33.0 – SdaThe 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.
    2. Ventilated Channel Cable Trays. Where 50 mm (2 in.), 75 mm (3 in.), 100 mm (4 in.), or 150 mm (6 in.) wide ventila‐ ted channel cable trays contain single-conductor cables, the sum of the diameters of all single conductors shall not exceed the inside width of the channel.
  3. Number of Type MV and Type MC Cables (2001 Volts or Over) in Cable Trays. The number of cables rated 2001 volts or over permitted in a single cable tray shall not exceed the requirements of this section.

The sum of the diameters of single-conductor and multicon‐ ductor cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Where single conduc‐ tor cables are triplexed, quadruplexed, or bound together in circuit groups, the sum of the diameters of the single conduc‐ tors shall not exceed the cable tray width, and these groups shall be installed in single layer arrangement.

392.30 Securing and Supporting.

  1. Cable Trays. Cable trays shall be supported at intervals in accordance with the installation instructions.
  2. Cables and Conductors. Cables and conductors shall be secured to and supported by the cable tray system in accord‐ ance with (1), (2) and (3) as applicable:
  1. In other than horizontal runs, the cables shall be fastened securely to transverse members of the cable runs.
  2. Supports shall be provided to prevent stress on cables where they enter raceways from cable tray systems.
  3. The system shall provide for the support of cables and raceway wiring methods in accordance with their corre‐ sponding articles. Where cable trays support individual conductors and where the conductors pass from one cable tray to another, or from a cable tray to raceway(s) or from a cable tray to equipment where the conductors are

terminated, the distance between the cable trays or between the cable tray and the raceway(s) or the equip‐ ment shall not exceed 1.8 m (6 ft). The conductors shall be secured to the cable tray(s) at the transition, and they shall be protected, by guarding or by location, from physi‐ cal damage.

392.46 Bushed Conduit and Tubing. 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.

392.56 Cable Splices. Cable splices made and insulated by approved methods shall be permitted to be located within a cable tray, provided they are accessible. Splices shall be permit‐ ted to project above the side rails where not subject to physical damage.

392.60 Grounding and Bonding.

  1. Metal Cable Trays. Metal cable trays shall be permitted to be used as equipment grounding conductors where continuous maintenance and supervision ensure that qualified persons service the installed cable tray system and the cable tray complies with provisions of this section. Metal cable trays that support electrical conductors shall be grounded as required for conductor enclosures in accordance with 250.96 and Part IV of Article 250. Metal cable trays containing only non-power conductors shall be electrically continuous through approved connections or the use of a bonding jumper.Informational Note: Examples of non-power conductors include nonconductive optical fiber cables and Class 2 and Class 3 Remote Control Signaling and Power Limiting Circuits.
    Table 392.22(B)(1) Allowable Cable Fill Area for Single-Conductor Cables in Ladder, Ventilated Trough, or Wire Mesh Cable Trays for Cables Rated 2000 Volts or Less
    imageMaximum Allowable Fill Area for Single-Conductor Cables in Ladder, Ventilated Trough, or Wire Mesh Cable TraysimageColumn 1
    Inside Width of Cable TrayApplicable for 392.22(B)(1)(b) OnlyColumn 2a Applicable for 392.22(B)(1)(c) Only
    mmin.
    mm2in.2
    mm2in.2502
    1,4002.0
    1,400 – (28 Sd)b2.0 – (1.1 Sd)b1004
    2,8004.5
    2,800 – (28 Sd)4.5 – (1.1 Sd)1506
    4,2006.5
    4,200 – (28 Sd)b6.5 – (1.1 Sd)b2008
    5,6008.5
    5,600 – (28 Sd)8.5 – (1.1 Sd)2259
    6,1009.5
    6,100 – (28 Sd)9.5 – (1.1 Sd)30012
    8,40013.0
    8,400 – (28 Sd)13.0 – (1.1 Sd)40016
    11,20017.5
    11,200 – (28 Sd)17.5 – (1.1 Sd)45018
    12,60019.5
    12,600 – (28 Sd)19.5 – (1.1 Sd)50020
    14,00021.5
    14,000 – (28 Sd)21.5 – (1.1 Sd)60024
    16,80026.0
    16,800 – (28 Sd)26.0 – (1.1 Sd)75030
    21,00032.5
    21,000 – (28 Sd)32.5 – (1.1 Sd)90036
    25,20039.0
    25,200 – (28 Sd)39.0 – (1.1 Sd)aThe maximum allowable fill areas in Column 2 shall be calculated. For example, the maximum allowable fill, in mm2, for a 150-mm wide cable tray in Column 2 shall be 4200 minus (28 multiplied by Sd) [the maximum allowable fill, in square inches, for a 6-in. wide cable tray in Column 2 shall be6.5 minus (1.1 multiplied by Sd)].bThe term Sd in Column 2 is equal to the sum of the diameters, in mm, of all cables 507 mm2 (in inches, of all 1000 kcmil) and larger single- conductor cables in the same cable tray with small cables.
    Table 392.60(A) Metal Area Requirements for Cable Trays Used as Equipment Grounding Conductor
    image
    1. The adjustment factors of 310.15(A)(3)(a) shall apply only to multiconductor cables with more than three current-carrying conductors. Adjustment factors shall be limi‐Maximum Fuse Ampere Rating, Circuit BreakerMinimum Cross-Sectional Area of Metalated to the number of current-carrying conductors in the cableand not to the number of conductors in the cable tray.Ampere Trip Setting, or Circuit Breaker ProtectiveSteel Cable TraysAluminum Cable Trays
    2. Where cable trays are continuously covered for moreimagethan 1.8 m (6 ft) with solid unventilated covers, not overRelay Ampere Trip Setting for                                                                         Ground-Fault Protection of Any Cable Circuit in the Cable95 percent of the allowable ampacities of Table 310.15(B)(16)and Table 310.15(B)(18) shall be permitted for multiconduc‐ tor cables.Tray Systemmm2 in.2 mm2 in.2
    3. Where multiconductor cables are installed in a single
    imagelayer in uncovered trays, with a maintained spacing of not less60 129 0.20 129 0.20100 258 0.40 129 0.20200 451.5 0.70 129 0.20400 645 1.00 258 0.40600967.51.50b2580.401000——3870.601200——6451.001600——967.51.502000——12902.00baTotal 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.
  2. Steel or Aluminum Cable Tray Systems. Steel or alumi‐ num cable tray systems shall be permitted to be used as equip‐ ment 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 392.60(A).
    3. All cable tray sections and fittings are legibly and durably marked to show the cross-sectional area of metal in chan‐ nel cable trays, or cable trays of one-piece construction, and the total cross-sectional area of both side rails for ladder or trough cable trays.
    4. Cable tray sections, fittings, and connected raceways are bonded in accordance with 250.96, using bolted mechani‐ cal connectors or bonding jumpers sized and installed in accordance with 250.102.
  3. Transitions. Where metal cable tray systems are mechani‐ cally discontinuous, as permitted in 392.18(A), a bonding jumper sized in accordance with 250.102 shall connect the two sections of the cable tray, or the cable tray and the raceway or equipment. Bonding shall be in accordance with 250.96.

392.80 Ampacity of Conductors.

  1. Ampacity of Cables, Rated 2000 Volts or Less, in Cable Trays.
    Informational Note: See 110.14(C) for conductor temperaturelimitations due to termination provisions.
    1. Multiconductor Cables. The allowable ampacity of multi‐ conductor cables, nominally rated 2000 volts or less, installed according to the requirements of 392.22(A) shall be as given in Table 310.15(B)(16) and Table 310.15(B)(18), subject to the provisions of (A)(1)(a), (b), (c), and 310.15(A)(2).than one cable diameter between cables, the ampacity shall not exceed the allowable ambient temperature-corrected ampaci‐ ties of multiconductor cables, with not more than three insula‐ ted conductors rated 0 through 2000 volts in free air, in accordance with 310.15(C).Informational Note: See Table B.310.15(B)(2)(3).
    2. Single-Conductor Cables. The allowable ampacity of single-conductor cables shall be as permitted by 310.15(A)(2). The adjustment factors of 310.15(B)(3)(a) shall not apply to the ampacity of cables in cable trays. The ampacity of single- conductor cables, or single conductors cabled together (triplexed, quadruplexed, etc.), nominally rated 2000 volts or less, shall comply with the following:
      1. Where installed according to the requirements of 392.22(B), the ampacities for 600 kcmil and larger single- conductor cables in uncovered cable trays shall not exceed 75 percent of the allowable ampacities in Table 310.15(B)(17) and Table 310.15(B)(19). Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 600 kcmil and larger cables shall not exceed 70 percent of the allowable ampacities in Table 310.15(B)(17) and Table 310.15(B)(19).
      2. Where installed according to the requirements of 392.22(B), the ampacities for 1/0 AWG through 500 kcmil single-conductor cables in uncovered cable trays shall not exceed 65 percent of the allowable ampacities in Table 310.15(B)(17) and Table 310.15(B)(19). Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 1/0 AWG through 500 kcmil cables shall not exceed 60 percent of the allowable ampacities in Table 310.15(B)(17) and Table 310.15(B)(19).
      3. Where single conductors are installed in a single layer in uncovered cable trays, with a maintained space of not less than one cable diameter between individual conductors, the ampacity of 1/0 AWG and larger cables shall not exceed the allowable ampacities in Table 310.15(B)(17) and Table 310.15(B)(19).Exception to (2)(3)(c): For solid bottom cable trays the ampacity of single conductor cables shall be determined by 310.15(C).
      4. Where single conductors are installed in a triangular or square configuration in uncovered cable trays, with a main‐ tained free airspace of not less than 2.15 times one conductor diameter (2.15 × O.D.) of the largest conductor contained within the configuration and adjacent conductor configura‐ tions or cables, the ampacity of 1/0 AWG and larger cables shall not exceed the allowable ampacities of two or three single insulated conductors rated 0 through 2000 volts supported on a messenger in accordance with 310.15(B).Informational Note: See Table 310.15(B)(20).392.80 ARTICLE 393 — LOW-VOLTAGE SUSPENDED CEILING POWER DISTRIBUTION SYSTEMS
    3. Combinations of Multiconductor and Single-Conductor Cables. Where a cable tray contains a combination of multi‐ conductor and single-conductor cables, the allowable ampaci‐ ties shall be as given in 392.80(A)(1) for multiconductor cables and 392.80(A)(2) for single-conductor cables, provided that the following conditions apply:
      1. The sum of the multiconductor cable fill area as a percentage of the allowable fill area for the tray calcula‐ ted in accordance with 392.22(A), and the single- conductor cable fill area as a percentage of the allowable fill area for the tray calculated in accordance with 392.22(B), totals not more than 100 percent.
      2. Multiconductor cables are installed according to 392.22(A), and single-conductor cables are installed according to 392.22(B) and 392.22(C).
  2. Ampacity of Type MV and Type MC Cables (2001 Volts or Over) in Cable Trays. The ampacity of cables, rated 2001 volts, nominal, or over, installed according to 392.22(C) shall not exceed the requirements of this section.
    Informational Note: See 110.40 for conductor temperature limi‐tations due to termination provisions.
    1. Multiconductor Cables (2001 Volts or Over). The allowa‐ ble ampacity of multiconductor cables shall be as given in Table 310.60(C)(75) and Table 310.60(C)(76), subject to the following provisions:
  1. Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, not more than 95 percent of the allowable ampacities of Table 310.60(C)(75) and Table 310.60(C)(76) shall be permit‐ ted for multiconductor cables.
  2. Where multiconductor cables are installed in a single layer in uncovered cable trays, with maintained spacing of not less than one cable diameter between cables, the ampacity shall not exceed the allowable ampacities of Table 310.60(C)(71) and Table 310.60(C)(72).

(2) Single-Conductor Cables (2001 Volts or Over). The ampacity of single-conductor cables, or single conductors cabled together (triplexed, quadruplexed, etc.), shall comply with the following:

  1. The ampacities for 1/0 AWG and larger single-conductor cables in uncovered cable trays shall not exceed 75 percent of the allowable ampacities in Table 310.60(C)(69) and Table 310.60(C)(70). Where the cable trays are covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 1/0 AWG and larger single- conductor cables shall not exceed 70 percent of the allow‐ able ampacities in Table 310.60(C)(69) and Table 310.60(C)(70).
  2. Where single-conductor cables are installed in a single layer in uncovered cable trays, with a maintained space of not less than one cable diameter between individual conductors, the ampacity of 1/0 AWG and larger cables shall not exceed the allowable ampacities in Table 310.60(C)(69) and Table 310.60(C)(70).
  3. Where single conductors are installed in a triangular or square configuration in uncovered cable trays, with a maintained free air space of not less than 2.15 times the diameter (2.15 × O.D.) of the largest conductor contained within the configuration and adjacent conduc‐ tor configurations or cables, the ampacity of 1/0 AWG

and larger cables shall not exceed the allowable ampaci‐ ties in Table 310.60(C)(67) and Table 310.60(C)(68).

Part III. Construction Specifications

392.100 Construction.

  1. Strength and Rigidity. Cable trays shall have suitable strength and rigidity to provide adequate support for all contained wiring.
  2. Smooth Edges. Cable trays shall not have sharp edges, burrs, or projections that could damage the insulation or jack‐ ets of the wiring.
  3. Corrosion Protection. Cable tray systems shall be corro‐ sion resistant. If made of ferrous material, the system shall be protected from corrosion as required by 300.6.
  4. Side Rails. Cable trays shall have side rails or equivalent structural members.
  5. Fittings. Cable trays shall include fittings or other suitable means for changes in direction and elevation of runs.
  6. Nonmetallic Cable Tray. Nonmetallic cable trays shall be made of flame-retardant material.

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