How to connect the ground wire of the cable tray in the low-voltage electrical shaft

The ground wire of a cable tray should be securely bonded to all tray sections and connected to the building grounding system using properly sized conductors and approved clamps or bonding jumpers.

Key Steps for Grounding a Cable Tray

1. Ensure Electrical Continuity Across the Tray All metallic cable tray sections must be electrically continuous. This includes bonding at splice points, elbows, tees, and other fittings. Use bonding jumpers where mechanical connections alone do not guarantee continuity . 2. Choose the Appropriate Grounding Conductor

• For steel trays, a bare or insulated copper conductor is commonly used.
• For aluminum trays, use an insulated conductor to prevent electrolytic corrosion, removing insulation only at bonding points with tin- or zinc-plated connectors .
• The conductor size must comply with NEC Table 250.122, sized to carry the maximum fault current expected in the tray . 3. Connect the Ground Wire to the Tray
• Use grounding clamps or bolted connections at each tray section or at alternate sections for mechanical stability and electrical continuity .
• For long runs, a continuous grounding conductor along the tray length is recommended to provide a reliable fault path . 4. Bond Parallel Tray Cables
• When multiple tray cables are installed in parallel, a single equipment grounding conductor sized according to NEC 250.122 can be used in combination with the individual cable grounds.
• Use split bolts or approved lugs to combine multiple ground wires until they match the available panel terminals . 5. Connect to the Building Grounding System
• The tray grounding system must be connected to the building's grounding electrode system to complete the fault current path .
• Ensure all metallic parts in the shaft, including supports and conduits, are bonded to maintain equipotentiality. 6. Verify and Inspect
• Check for continuity across all tray sections and fittings.
• Ensure all connections are tight, corrosion-resistant, and mechanically secure.
• Confirm compliance with NEC Article 392 and local electrical codes . By following these steps, the cable tray system will provide a safe, low-resistance path for fault currents, protecting personnel and equipment while maintaining code compliance.