Not all cables are laid in cable trays; only specific tray-rated cables are permitted, and their use depends on safety, code compliance, and environmental conditions.

Cable Tray Usage and Limitations

Cable trays are widely used for organizing and supporting power, control, communication, and data cables in industrial, commercial, and some institutional settings, providing easy access for maintenance and scalability . However, not all cables can be installed in cable trays. The National Electrical Code (NEC) Article 392 specifies which cables are approved for tray use, including tray cable (TC), metal-clad (MC), and certain exposure-rated (ER) cables . These cables are designed to withstand heat, moisture, and physical stress typical in tray installations.

Situations Where Cable Trays Are Not Suitable

Cable trays are not suitable in all locations. They are prohibited in hoistways, areas subject to severe physical damage, or enclosed spaces where maintenance access is restricted . Nonmetallic trays have additional limitations, such as use only in corrosive environments or where voltage isolation is required. In plenum spaces, fire-rated ties must be used instead of standard plastic ties to reduce toxic smoke risk during a fire .

Installation Considerations

When using cable trays, several factors must be considered:

• Tray Fill Limits: Power cables should not exceed 40% of the tray cross-section, and control cables 50% .
• Separation: High-power and low-power cables must be separated to prevent electromagnetic interference (EMI), .
• Support and Grounding: Metallic trays must be properly grounded and bonded, and cables must be supported according to NEC spacing requirements .
• Environmental Protection: Outdoor or sunlight-exposed installations require sunlight-resistant cables and expansion splice plates to accommodate thermal expansion .

Summary

While cable trays are versatile and efficient for many types of cables, their use is limited to approved tray-rated cables and suitable environments. Non-tray-rated cables, areas prone to damage, or enclosed spaces may require alternative wiring methods such as conduits or raceways. Proper adherence to NEC standards ensures safety, reliability, and compliance during installation .