How to ground a suspended cable tray

A suspended cable tray should be grounded by connecting it to the facility's grounding system using bonding jumpers or a continuous grounding conductor, ensuring all tray sections are electrically connected and compliant with NEC requirements.

Steps to Ground a Suspended Cable Tray

1. Inspect and Plan Before Installation Before installing cables, verify that the tray system is designed for grounding and that all sections are compatible with bonding. Grounding inspection is easier and safer when the tray is empty, allowing you to check continuity and connections before energizing the system . 2. Choose the Grounding Method There are three main options for providing an Equipment Grounding Conductor (EGC) in a cable tray system:

• Use an EGC conductor in or on the cable tray.
• Use each multi-conductor cable's individual EGC.
• Use the metal cable tray itself as the EGC, if it meets conductivity and strength requirements . 3. Bond Tray Sections Together If using a separate EGC, bond it to each or alternate tray sections using grounding clamps, bolts, or welds. This ensures mechanical stability and electrical continuity, preventing the EGC from being displaced under fault currents . For aluminum trays, avoid bare copper conductors to prevent galvanic corrosion; use insulated conductors with insulation removed only at bonding points and tin- or zinc-plated connectors . 4. Connect to the Facility Grounding System Run a continuous grounding conductor from the tray system to the main grounding bus or electrode. Ensure the conductor is sized according to NEC Table 250.122 and the tray's cross-sectional area meets the minimum requirements for the intended fault current . 5. Verify Low Grounding Resistance The grounding system should have a resistance ideally 4 ohms or less to ensure effective fault current dissipation . Test continuity along the tray and between the tray and the main grounding system. 6. Material Selection Use materials with good conductivity and corrosion resistance:
• Copper wire for excellent conductivity.
• Hot-dip galvanized steel for durability.
• Stainless steel for harsh or corrosive environments . 7. Inspection and Maintenance After installation, inspect all connections, clamps, and bonding points for tightness and corrosion. Periodically recheck continuity and grounding resistance to maintain safety and system reliability . By following these steps, a suspended cable tray can be safely grounded, providing a low-impedance path for fault currents, minimizing electrical hazards, and ensuring compliance with NEC standards .