Should power cables be placed in cable trays

Yes, power cables can be run in cable trays, provided they are properly rated, spaced, and installed according to NEC 392 and industry best practices.

Cable Tray Usage for Power Cables

Cable trays are widely used in industrial, commercial, and large-scale facilities to support and route power cables, feeders, branch circuits, and control circuits . They provide a rigid support system that simplifies installation, maintenance, and future upgrades. Power cables installed in trays must be Type TC (Tray Rated) or metal-armored (Type MC) to withstand exposure to open air and mechanical stress .

Tray Types and Considerations

• Ladder trays: Most common for power cables; excellent ventilation reduces overheating and allows easy cable management .
• Ventilated trough trays: Provide moderate ventilation and better support for smaller cables; suitable for medium-voltage installations .
• Solid-bottom trays: Offer maximum protection from debris or fluids but reduce heat dissipation, requiring stricter fill limits .

Fill Limits and Separation

• Power cables should not exceed 40% of the tray's cross-sectional area to prevent overheating .
• High-power and low-power (signal or control) cables must be separated to avoid electromagnetic interference (EMI). Industry best practice is 12 inches of vertical separation or separate trays for sensitive signal cables .
• For variable frequency drive (VFD) output cables, additional separation or shielding is recommended to prevent noise coupling .

Ampacity and Heat Considerations

Cables in trays experience reduced ampacity compared to free-air installations due to restricted airflow and mutual heating effects when bundled . Metal trays can also induce eddy currents, slightly increasing conductor resistance. Proper derating calculations, following IEC 60287 or NEC guidelines, are essential to ensure safe current-carrying capacity .

Installation Best Practices

• Use sunlight-resistant cables for outdoor trays and expansion splice plates to accommodate thermal expansion .
• Ensure proper bonding and grounding; cable trays can serve as an Equipment Grounding Conductor if installed according to NEC 392.60 .
• Maintain clear access for inspection and maintenance, as trays are intended for open-air support rather than enclosed conduit protection . In summary, power cables can safely be run in cable trays when using the correct cable type, adhering to fill limits, maintaining separation from sensitive circuits, and accounting for ampacity derating. Following NEC 392 and industry best practices ensures both safety and long-term reliability.