Cable tray bridging copper conductors

Copper wires in cable trays should be properly bonded and grounded using clamps or connectors, avoiding direct bare copper contact with aluminum trays to prevent corrosion.

Grounding and Bonding Practices

When using copper wires in a cable tray system, the tray itself can serve as an Equipment Grounding Conductor (EGC) if installed according to code requirements, but additional bonding is recommended for safety and mechanical stability. Each multi-conductor cable with its own EGC should be connected to the tray using grounding clamps at each or alternate tray sections. This ensures electrical continuity and prevents the EGC from being displaced by magnetic forces during fault conditions.

Material Compatibility

Aluminum trays: Avoid placing bare copper conductors directly in aluminum trays, as this can cause electrolytic corrosion in moist environments. Instead, use insulated copper conductors and remove insulation only at bonding points with tin- or zinc-plated connectors. Steel trays: Steel trays can be used as EGCs for circuits with ground-fault protection below 600 amperes, while aluminum trays are limited to 2000 amperes.

Mechanical Considerations

Copper wires should be mechanically secured to the tray to prevent movement under fault currents. Grounding clamps not only provide electrical bonding but also anchor the EGC to the tray, maintaining safety during high-current events. For ladder or trough trays, ensure the minimum cross-sectional area of the tray side rails meets the requirements for the intended fault current rating.

Best Practices

Use insulated copper conductors when bridging sections of aluminum trays. Bond each tray section or alternate sections to maintain continuity. Avoid bare copper in corrosive environments; use plated connectors for bonding.

Verify tray material and size meet NEC requirements for grounding and fault protection. Ensure proper spacing and support of cables to prevent mechanical stress on copper wires. By following these practices, copper wires can be safely and effectively bridged across cable tray systems, ensuring both electrical safety and long-term reliability.