Cable tray and cable tray connection ground wire

A properly grounded cable tray can serve as an Equipment Grounding Conductor (EGC), but connections must ensure electrical continuity and compliance with NEC standards. Using Cable Trays as Grounding ConductorsMetallic cable trays, such as steel or aluminum, can be used as the Equipment Grounding Conductor (EGC) if they meet NEC requirements and are UL-Classified for this purpose. This allows the tray itself to safely carry fault currents back to the power source, reducing the need for separate green grounding wires in some installations.

However, the tray must provide a continuous low-impedance path, and any paint, rust, or corrosion at joints should be removed to maintain conductivity.

Ground Wire Connections

If a separate EGC is used, it should be bonded to each or alternate cable tray sections using grounding clamps. This ensures that under fault conditions, the EGC remains securely anchored and maintains electrical continuity. For aluminum trays, a bare copper wire should be avoided due to potential electrolytic corrosion; instead, use an insulated conductor with insulation removed at bonding points and tin- or zinc-plated connectors.

NEC Compliance

Article 392 governs cable tray systems, including grounding and bonding requirements. Article 250 specifies that all metallic trays must be grounded, regardless of whether they are used as an EGC. The cross-sectional area of the tray metal must meet minimum requirements to safely carry fault currents based on the protective device rating.

If the tray's metal area is insufficient, a separate EGC must be installed in the tray or within each cable.

Best Practices

Ensure low grounding resistance, ideally 4 ohms or less, to improve safety and system stability. Remove paint or coatings at connection points to maintain electrical continuity. Use insulated conductors in aluminum trays to prevent corrosion.

Verify that the tray is UL-Classified for use as an EGC if relying on the tray itself for grounding. For wire mesh trays supporting signal or control cables, a separate grounding conductor is usually not required if the tray has a low-impedance path to a non-system ground. By following these guidelines, cable tray systems can provide a safe, reliable grounding path, protecting personnel and equipment from electrical faults while ensuring compliance with NEC standards.