How to connect cable trays and cable tray ground wires

To connect a ground wire to a cable tray, use a properly sized equipment grounding conductor (EGC) bonded securely to each tray section with grounding clamps or bolts, ensuring continuous electrical continuity and compliance with NEC standards. Key Steps for Grounding a Cable Tray1. Determine the Grounding Method There are three common approaches for providing an EGC in a cable tray system: Running a separate EGC conductor along or inside the cable tray.

Using the EG

C built into each multi-conductor cable. Using the metallic cable tray itself as the EGC if it meets NEC conductivity and strength requirements. 2.

Bonding the Ground Wire

If a separate EGC is used, bond it to each or alternate cable tray sections using grounding clamps, bolts, or welds to maintain electrical continuity. Ensure that the connection is mechanically secure so that fault currents or magnetic forces do not dislodge the conductor. For aluminum trays, avoid bare copper conductors to prevent electrolytic corrosion; use insulated conductors and remove insulation only at bonding points with tin- or zinc-plated connectors.

3.

Verify Electrical Continuity

All tray sections, fittings, and splices must maintain a conductive path across the entire system. Use bonding jumpers at splice points where mechanical connections alone may not ensure continuity. 4.

Connect to the Building Grounding SystemThe EGC or tray must be securely connected to the building's grounding electrode system to complete the fault current path. Proper sizing of the grounding conductor should follow NEC tables (e.g., Table 250. 122) to safely carry potential fault currents.

5.

Material Selection

Use materials with good conductivity and corrosion resistance, such as copper, stainless steel, or hot-dip galvanized steel. Ensure the grounding wire is kept clear of moisture, flammable materials, or corrosive environments. 6.

Testing and Compliance

Measure grounding resistance to ensure it is ideally 4 ohms or less for effective fault current diversion. Confirm that the installation meets NEC Article 392 requirements for metallic cable trays, including bonding, continuity, and grounding. By following these steps, the cable tray system will provide a safe, low-resistance path for fault currents, protecting personnel and equipment while maintaining NEC compliance.