Metal grounding of cable trays

Metal cable trays must be properly grounded to provide a low-impedance path for fault currents, ensuring safety, equipment protection, and NEC compliance.Importance of GroundingGrounding metal cable trays is essential for personnel safety, equipment protection, and system reliability. Proper grounding provides a safe path for fault currents, reduces the risk of electric shock, prevents equipment damage from overvoltage, and minimizes fire hazards caused by excessive heat during fault conditions. It also helps dissipate energy from lightning strikes and reduces electromagnetic interference (EMI), maintaining signal integrity for sensitive electronic systems .NEC RequirementsThe National Electrical Code (NEC) Article 392 governs cable tray systems. All metallic trays must be electrically continuous, bonded at splice points, and connected to the building's grounding system. Steel trays cannot serve as equipment grounding conductors for circuits with ground-fault protection above 600 amperes . If a tray is used as an equipment grounding conductor (EGC), it must be marked as suitable for this purpose and meet minimum cross-sectional area requirements .Grounding PracticesBonding Jumpers: Use bonding jumpers or grounding clamps to connect tray sections, ensuring electrical continuity and mechanical stability under fault conditions .Equipment Grounding Conductors: If trays are not rated as EGCs, install a separate insulated or bare conductor in the tray, bonded to each section .Material Considerations: Avoid bare copper in aluminum trays to prevent electrolytic corrosion; use insulated conductors with tin or zinc-plated connectors .Inspection: Grounding should be inspected before energizing the system. Verify continuity with a multimeter; resistance should be very low (typically