NEC Article 392 explains cable trays, their components, appropriate wiring methods for cable trays, and instances where they are and are not permitted for use. It also focuses on construction and installation practices for cable trays.

Here is the summary of the main points found in NEC Article 392:

Cable tray use permitted

• Cable trays can be used as a support system for various wiring methods, including service conductors, feeders, branch circuits, communications circuits, control circuits, and signaling circuits (392.3).
• Cable trays are used not just in industrial establishments. Cable trays are permitted for use in any type of building or structure, provided they comply with the relevant installation and support requirements outlined in NEC Article 392.
• According to NEC Article 392.10(B)(1), the smallest size single conductor allowed to be installed in a cable tray is 1/0 AWG.
• For the installation of single conductor cables sized 1/0 AWG to 4/0 AWG in industrial establishments, the NEC specifies the maximum allowable rung spacing for the cable tray. According to NEC Article 392.10(B)(1)(c), the maximum allowable rung spacing for cable trays supporting these sizes of single conductor cables is 9 inches (229 mm).

Multiconductor cables permitted in trays

• Some of the multiconductor cables allowed for use as per NEC 392.3 are:
• Type AC (Armored Cable)
• Type MC (Metal-Clad Cable)
• Type MI (Mineral-Insulated Cable)
• Type TC (Tray Cable)
• Type PLTC (Power Limited Tray Cable)
• Type ITC (Instrumentation Tray Cable)
• Type MV (Medium Voltage Cable)
• Type SE (Service Entrance Cable)
• Type USE (Underground Service Entrance Cable)

Communication and control cables:

• Type CM (Communications Cable)
• Type CMG (General-Purpose Communications Cable)
• Type CMP (Plenum Communications Cable)
• Type CMR (Riser Communications Cable)
• Type CL2 (Class 2 Cable)
• Type CL3 (Class 3 Cable)

Optical Fiber Cables:

• Type OFC (Optical Fiber Conductive Cable)
• Type OFN (Optical Fiber Nonconductive Cable)
• Type OFNP (Optical Fiber Nonconductive Plenum Cable)
• Type OFNR (Optical Fiber Nonconductive Riser Cable)

Cable and conductor installation

• Cables rated for different voltages can be installed in the same tray, but those operating above 600 volts must either be of Type MC or separated by a solid barrier from lower voltage cables​.
• Cables rated 600 volts or less can be installed together in the same cable tray without additional separation, provided they meet the NEC requirements for fill and support​.

392.30 securing and supporting

• Cables and conductors must be secured to the cable tray at intervals according to installation instructions.
• For non-horizontal runs, cables should be fastened securely to transverse members of the cable tray.
• Supports must be provided to prevent stress on cables where they enter raceways from cable tray systems.
• Cable ties used must be listed and identified for securement and support​.