Cable trays, especially metallic ones, can serve as Equipment Grounding Conductors (EGC) if they meet NEC requirements, ensuring electrical continuity across sections and connections . All tray sections should be electrically continuous, bonded through bolts, splice plates, clamps, or bonding jumpers where gaps exist . Both side rails of ladder or trough trays must be bonded together and connected back to the power source or main grounding system . For non-metallic trays, a separate EGC can be installed within the tray to provide grounding continuity .
When cable trays are located on rooftops, outdoors, or in areas exposed to lightning, they should be integrated with the building's lightning protection system as per NFPA780 standards . This involves connecting the tray system to the overhead lightning protection conductors and ensuring the grounding resistance is low enough to safely dissipate lightning currents. Overhead cable systems can provide additional protection by diverting lightning away from sensitive circuits .
Regular inspection is critical. Check bonding jumpers connecting tray sections with a multimeter; a low resistance reading (less than 0.01 ohms) indicates proper grounding . Pay attention to joints, bolts, and splice plates, as vibrations or loose connections can compromise grounding. Aluminum trays form a protective oxide layer but still require proper bonding to prevent shock hazards .
To ensure effective lightning protection for cable trays:
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