Cable tray system grounding

Cable trays must be properly grounded and bonded to ensure electrical safety, prevent shock hazards, and maintain system reliability.

Grounding Cable Trays

Grounding a cable tray involves connecting the metallic tray to the earth to safely discharge fault currents. This provides a low-resistance path for stray electrical currents, reducing the risk of electric shock, equipment damage, or fire hazards . All metallic cable trays must be grounded according to NEC Article 250.96, regardless of whether the tray is used as an equipment grounding conductor (EGC), .

Using Cable Trays as Equipment Grounding Conductors

In some installations, the cable tray itself can serve as the EGC. To qualify, the tray must meet minimum cross-sectional area requirements based on the maximum fuse rating or circuit breaker trip setting . Steel trays should not be used as EGCs for circuits with ground-fault protection above 600 amperes, and aluminum trays should not be used above 2000 amperes . When using the tray as an EGC, ensure all tray sections are electrically continuous and mechanically tight, with bonding jumpers added if necessary .

Bonding Practices

Bonding ensures electrical continuity between all parts of the tray system, preventing voltage differences and reducing the risk of arcing or interference . Grounding clamps or connectors are commonly used to bond the tray to an EGC wire or to adjacent tray sections. For aluminum trays, insulated conductors are preferred to avoid electrolytic corrosion, with insulation removed only at bonding points using tin- or zinc-plated connectors .

Installation Best Practices

• Verify that the grounding resistance is low, ideally 4 ohms or less, to ensure effective fault current diversion .
• Keep grounding wires clear of flammable materials and corrosive environments .
• Ensure mechanical connections are tight and electrically continuous across all tray sections .
• Use approved tray-rated cables and maintain proper tray fill to avoid overheating or physical damage . By following these grounding and bonding practices, cable tray systems can safely manage electrical faults, comply with NEC and international standards, and maintain reliable operation in industrial, commercial, or data center environments.