Where should the cable tray ground wire be connected

The ground wire for a cable tray should be connected to the tray itself or to a dedicated equipment grounding conductor (EGC) that is bonded to the building's grounding system.

Grounding Metallic Cable Trays

Metallic cable trays must be grounded to ensure safety and prevent electrical shock hazards. The ground wire, or equipment grounding conductor (EGC), provides a path for stray electricity to safely return to the power source, allowing circuit breakers to trip in case of a fault.

Connection Methods

Using the Cable Tray as the Grounding ConductorIf the tray is metallic and meets NEC conductivity and strength requirements, it can serve as the EGC itself. Each tray section should be electrically bonded to adjacent sections using grounding clamps, bolts, or welds to maintain continuity.

Full-

Length Grounding Conductor

A continuous grounding wire can be run along the length of the tray. This conductor should be securely bonded to each tray section, ensuring a reliable path for fault currents.

EG

C Installed in or on the TrayAn insulated or bare copper EGC can be placed inside or mounted on the tray. For aluminum trays, insulated conductors are preferred to prevent electrolytic corrosion, with insulation removed at bonding points to connect to the tray, raceways, or equipment enclosures using tin- or zinc-plated connectors.

Best Practices

Bonding at Each Section: Even if not required by NEC, bonding the EGC to each or alternate tray sections is recommended to prevent the EGC from being displaced under fault current conditions. Material Considerations: Copper is preferred for conductivity, while stainless steel or galvanized steel may be used for mechanical strength and corrosion resistance. Grounding Resistance: Maintain a low grounding resistance, ideally 4 ohms or less, to ensure effective fault current dissipation.

Compliance: Follow NEC Article 392 for cable tray systems and Article 250 for grounding requirements.

Summary

The ground wire should either bond directly to the metallic tray or run as a dedicated EGC along the tray, with secure connections at each section. Proper grounding ensures safety, prevents the tray from becoming energized, and maintains compliance with NEC standards.