How to ground cable trays troughs

Cable trays and troughs should be grounded using either the tray itself as an equipment grounding conductor or by connecting dedicated grounding conductors with proper clamps and materials to ensure electrical safety.

Key Principles of Grounding Cable Trays

Purpose of grounding: Grounding cable trays provides a safe path for stray electrical currents, preventing electric shocks, equipment damage, and fire hazards. It also reduces electrical noise and interference in sensitive installations . Regulatory compliance: 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), . Grounding ensures the system is electrically continuous and capable of safely conducting fault currents .

Methods for Grounding

1. Using the cable tray as the EGC:
   • Metal trays can serve as the EGC if they meet the minimum cross-sectional area requirements for the expected fault current .
   • Steel trays are limited to circuits with ground-fault protection below 600 A, and aluminum trays below 2000 A .
   • Sections of the tray should be electrically bonded using grounding clamps or connectors to maintain continuity .
2. Using a dedicated grounding conductor:
   • Run a continuous insulated or bare copper conductor along the tray length, bonded to each tray section with clamps or lugs .
   • Avoid bare copper in aluminum trays to prevent electrolytic corrosion; use insulated conductors with exposed ends at bonding points .
   • Flexible jumpers can be used at connection points to maintain electrical continuity and mechanical stability .
3. Connection techniques:
   • Use tin- or zinc-plated connectors, bolts, or welds to secure grounding conductors to the tray .
   • Ensure all connections are tight and corrosion-resistant to maintain low impedance and effective fault current conduction .

Material Considerations

• Steel trays: Durable and suitable for heavy-duty applications; can serve as EGC within current limits .
• Aluminum trays: Lightweight and corrosion-resistant; avoid direct contact with bare copper .
• Non-metallic trays: Cannot be used as grounding conductors; require separate grounding lines .

Best Practices

• Plan grounding points and conductor routing during system design .
• Maintain grounding resistance ideally below 4 ohms for effective fault current diversion .
• Bond cable screens to the grounding system at both ends of the cable .
• Use bimetallic washers when connecting dissimilar metals to prevent galvanic corrosion . Proper grounding of cable trays ensures safety, regulatory compliance, and system stability, making it a critical step in electrical installations.