Cable tray ground

All metallic cable trays, including those installed on the ground, must be properly grounded to ensure electrical safety and compliance with NEC standards.Grounding RequirementsWhen a cable tray is placed on the ground, it must be grounded regardless of whether it is used as an equipment grounding conductor (EGC), as required by NEC Article 250.96 . Grounding provides a safe path for fault currents, preventing electric shocks and equipment damage . There are three main options for grounding cable trays:Using a separate EGC conductor inside or attached to the tray.Each multi-conductor cable with its own EGC.Using the cable tray itself as the EGC in qualifying facilities, provided it meets the minimum metal cross-sectional area requirements outlined in NEC Table 392.60(A), .Material and Corrosion ConsiderationsAluminum trays should not have bare copper grounding conductors due to the risk of electrolytic corrosion in moist environments. Use insulated conductors with insulation removed only at bonding points, and connect with tin- or zinc-plated connectors .Steel trays are limited to circuits with ground-fault protection up to 600 amperes, while aluminum trays can handle up to 2,000 amperes .Installation PracticesEnsure the tray is electrically continuous and mechanically secured to prevent movement of the EGC under fault conditions .If using the tray as the EGC, verify that the cross-sectional area of the tray side rails meets NEC requirements for the intended circuit load .Maintain low grounding resistance, ideally 4 ohms or less, to ensure effective fault current dissipation .Avoid placing trays in enclosed spaces or hoistways; they must remain accessible for maintenance .Additional Safety TipsKeep grounding wires clear of flammable or corrosive materials.Use hot-dip galvanized steel, copper, or stainless steel for grounding conductors to ensure durability and corrosion resistance .For wire mesh trays supporting cables with built-in EGCs, a separate grounding conductor is usually not required, but the tray should have a low-impedance path to a non-system ground to reduce noise and stray currents . Proper grounding of cable trays on the ground ensures electrical safety, compliance with NEC standards, and long-term reliability of the electrical system .