Article 392 Cable Trays
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.
Table 392.10(A) Wiring Methods
|Armored cable: Type AC||320|
|Class 2 and Class 3 cables||725|
|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|
(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.
Informational Note: Federal Aviation Administration (FAA) Advisory Circulars (ACs) provide additional practices and methods for airport lighting.
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.
- The cables operating at over 1000 volts are Type MC.
- 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.
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.
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|
|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.|
(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.