Grounding requirements for cable tray corners

Corners of metallic cable trays should be properly bonded and grounded to maintain electrical continuity and safety, either by connecting a grounding conductor or using the tray itself as the equipment grounding conductor.Key Principles for Grounding Cable Tray Corners1. Use of Cable Tray as Equipment Grounding Conductor (EGC) Metallic cable trays can serve as the EGC if they meet NEC requirements, ensuring that any fault current is safely conducted to ground . This includes corners, bends, and junctions, which must maintain electrical continuity with the rest of the tray system. 2. Bonding at Corners At corners or bends, it is recommended to use grounding clamps or bonding jumpers to connect adjacent tray sections. This ensures that the corner does not become a weak point in the grounding path and prevents the EGC from being displaced under fault current conditions . For aluminum trays, insulated conductors with exposed ends at bonding points are preferred to avoid electrolytic corrosion . 3. Grounding Conductor Installation If a separate grounding conductor is used, it should run along the tray and be securely attached at corners using clamps or bolted connections. The conductor should maintain low resistance (ideally 4 ohms or less) to ensure effective fault current diversion . Continuous grounding conductors along the tray length are recommended for reliability. 4. Material ConsiderationsSteel trays: Can be used as EGC for circuits with ground-fault protection up to 600 A.Aluminum trays: Can be used as EGC for circuits up to 2000 A, but avoid bare copper conductors in moist environments to prevent corrosion .Connectors: Tin or zinc-plated connectors are recommended for bonding points at corners . 5. Compliance and Safety All metallic trays must be grounded according to NEC Article 250.96, regardless of whether the tray is used as an EGC . Proper grounding at corners reduces the risk of electric shock, prevents static buildup, and ensures safe maintenance operations .Practical TipsInspect corners for tight mechanical and electrical connections.Use insulated jumpers where corrosion is a concern.Ensure continuity testing after installation to verify low-resistance grounding.Avoid placing bare copper directly in aluminum trays in humid environments. By following these practices, grounding at cable tray corners will maintain system safety, comply with NEC standards, and provide reliable fault current paths.