Cable Tray Grounding Installation

Proper grounding of cable trays ensures electrical safety by providing a reliable path for fault currents, preventing shocks, equipment damage, and fire hazards.

Key Principles of Cable Tray Grounding

Metallic cable trays must be grounded according to NEC Article 250. 96, regardless of whether the tray itself is used as an equipment grounding conductor (EGC) or an additional EGC is installed. Grounding provides a safe path for stray currents, protecting personnel and equipment from electrical faults.

Equipment Grounding Conductor (EGC) OptionsThere are three main methods to provide grounding in a cable tray system: Tray as EGC: The metallic tray itself can serve as the EGC if it meets NEC Table 392. 60(A) requirements for metal cross-sectional area.

EG

C in or on the tray: A separate insulated or bare conductor runs along the tray and is bonded to each tray section using grounding clamps. This ensures mechanical stability and electrical continuity under fault conditions. Individual cable EGCs: Each multi-conductor cable may include its own EGC, which can be bonded to the tray sections for added safety.

Bonding Practices

Grounding clamps are recommended to bond the EGC to each or alternate tray sections. This not only ensures electrical continuity but also mechanically secures the conductor against magnetic forces during fault currents. Material compatibility is critical: avoid bare copper EGCs in aluminum trays to prevent electrolytic corrosion.

Use insulated conductors with insulation removed only at bonding points, and employ tin- or zinc-plated connectors.

Installation Considerations

Resistance: The grounding system should maintain a low resistance, ideally 4 ohms or less, to ensure effective fault current diversion. Clearances and accessibility: Maintain proper vertical clearance above trays for installation and maintenance, and avoid prohibited areas such as hoistways. Compliance: Follow NEC Article 392 for tray fill limits, cable separation, and approved cable types to ensure overall system safety.

Safety Tips

Keep grounding conductors away from flammable or corrosive materials. Inspect bonding connections regularly to ensure continuity and prevent loosening over time. Use proper torque and connectors to maintain reliable electrical and mechanical connections.

By following these grounding and bonding practices, cable tray installations will meet NEC requirements, reduce the risk of electrical hazards, and ensure long-term system reliability.