Connecting ground wires between cable trays

Ground wires between cable trays should be securely bonded to ensure electrical continuity, safety, and compliance with NEC standards.

Purpose of Grounding Cable Trays

Grounding cable trays provides a low-impedance path for fault currents, protecting personnel and equipment from electric shock, fire hazards, and equipment damage due to overvoltage or insulation failure. Proper grounding also helps minimize electromagnetic interference (EMI) and improves system reliability.

Methods for Connecting Ground Wires

Using the Cable Tray as the Equipment Grounding Conductor (EGC) Metal cable trays can serve as the EGC if they meet NEC requirements for conductivity and cross-sectional area. In this case, the tray itself provides a continuous grounding path, but bonding between tray sections is essential to maintain electrical continuity. Running a Full-Length Grounding Conductor A continuous grounding wire can be installed along the length of the tray.

This wire should be securely connected at each tray section using grounding clamps, bolts, or welds to prevent breaks and ensure mechanical stability under fault conditions. Bonding at Tray Joints When connecting multiple tray sections, bonding clamps or plated connectors (tin or zinc) are recommended to electrically and mechanically join the trays. This ensures that fault currents can safely flow through the grounding system and prevents the EGC from being displaced by magnetic forces during a fault.

Material Considerations

Copper wire: Excellent conductivity and corrosion resistance, ideal for most installations. Insulated conductors: Recommended for aluminum trays to prevent electrolytic corrosion; remove insulation at bonding points. Galvanized or stainless steel: Suitable for harsh environments with high corrosion potential.

Best Practices

Ensure electrical continuity across all tray sections. Avoid placing bare copper in aluminum trays in moist environments; use insulated conductors with proper bonding. Maintain low grounding resistance, ideally 4 ohms or less, to ensure effective fault current dissipation.

Follow NE

C Article 392 and other relevant sections (e.g., 250. 96, 250-51) for grounding and bonding requirements. By following these practices, cable tray systems will provide a safe, reliable, and code-compliant grounding path, protecting both personnel and equipment while maintaining system performance.