Installation length of ground cable trays

The typical installation length or support span for ground cable trays ranges from 6 to 10 feet for standard trays, and up to 20 feet for heavy-duty, long-span trays, depending on load and manufacturer specifications.

Support Span Guidelines

For proper installation, cable trays must be supported at intervals that prevent mechanical stress on the cables and maintain grounding integrity. Standard trays generally require supports every 6 to 10 feet, while heavy-duty or long-span trays can extend up to 20 feet between supports . The exact spacing depends on the tray type, material (steel, aluminum, or FRP), and the total weight of the cables being carried . Manufacturer load charts should always be consulted to ensure compliance and safety.

Grounding Considerations

All metallic cable trays must be grounded according to NEC Article 250.96, even if the tray itself is not used as an equipment grounding conductor (EGC), . Grounding can be achieved in several ways:

• Full-length grounding conductor: A continuous wire runs along the tray, providing a reliable path for fault currents .
• Tray as EGC: The metallic tray itself can serve as the grounding conductor if it meets conductivity and cross-sectional area requirements .
• Bonding at joints: Grounding wires or clamps are used at tray connections to maintain electrical continuity and mechanical stability . For installations using a separate EGC, a minimum #4 AWG conductor is recommended, either inside or attached to the tray . Multi-conductor cables with individual EGCs can also be used, and all connections must be mechanically secure to prevent disconnection under fault conditions .

Additional Installation Tips

• Unsupported spans to equipment: When transitioning cables from a tray to equipment or another raceway, the unsupported distance should not exceed 6 feet; otherwise, additional supports are required .
• Thermal expansion: For long outdoor runs, expansion splice plates should be installed to accommodate thermal movement .
• Cable fastening: Cables should be secured to transverse members in vertical or angled runs and tied in horizontal runs to maintain spacing and improve heat dissipation . By following these guidelines, ground cable trays can be installed safely, maintain proper grounding, and comply with NEC standards, ensuring both electrical safety and mechanical reliability.