How to ground cable tray supports

Grounding a cable tray involves connecting it to the facility's grounding system using proper conductors and bonding methods to ensure safety and low-impedance fault paths.

Key Principles

All metallic cable trays must be grounded to provide a safe path for fault currents, protect personnel, and prevent equipment damage, regardless of whether the tray itself is used as an equipment grounding conductor (EGC) (NEC Article 250. 96). Grounding also helps minimize electromagnetic interference (EMI) and protects against lightning strikes.

Methods of Grounding

Using a Separate Grounding ConductorRun a continuous insulated grounding wire along the length of the cable tray. Bond the conductor to each or alternate tray sections using grounding clamps to ensure electrical continuity and mechanical stability under fault conditions. Avoid bare copper in aluminum trays to prevent electrolytic corrosion; use insulated conductors with insulation removed only at bonding points.

Using the Cable Tray as the Grounding ConductorOnly applicable for metallic trays that meet NEC conductivity and cross-sectional area requirements (see NEC Table 392. 60(A)). Steel trays should not be used as EGCs for circuits with ground-fault protection above 600 A, and aluminum trays above 2000 A.

Ensure all tray sections are electrically continuous and bonded at joints. Bonding at Joints and Equipment ConnectionsUse tin- or zinc-plated connectors, bolts, or welds to bond the grounding conductor to tray sections, raceways, and equipment enclosures. Maintain low grounding resistance (ideally ≤ 4 ohms) to ensure effective fault current diversion.

Material Considerations

Copper Wire: Excellent conductivity, corrosion-resistant, preferred for most installations.

Hot-

Dip Galvanized Steel: Durable and corrosion-resistant, suitable for industrial environments. Stainless Steel: Ideal for harsh or corrosive environments.

Best Practices

Ensure grounding paths are permanent, electrically continuous, and capable of safely conducting fault currents. Avoid routing grounding conductors near flammable or corrosive materials. Inspect and maintain connections regularly to prevent loosening or corrosion.

For wire mesh trays supporting cables with built-in EGCs, a separate grounding conductor may not be required if a low-impedance path to a non-system ground exists. By following these methods and adhering to NEC requirements, cable tray grounding ensures safety, system reliability, and protection against electrical hazards.