Grounding wire of indoor cable tray

Yes, indoor metallic cable trays generally require grounding, either through a dedicated grounding wire or by using the tray itself if it meets code requirements.

NEC and Safety Requirements

According to the National Electrical Code (NEC), all metallic cable trays must be grounded to ensure safety, regardless of whether the tray is used as an equipment grounding conductor (EGC) or not. Grounding provides a low-impedance path for fault currents, protecting personnel and equipment from electric shock, fire, and equipment damage. Even in indoor environments, grounding is essential to maintain system reliability and safety.

Methods of Grounding

Dedicated Grounding Wire: A continuous grounding conductor can be run along the length of the cable tray, securely connected at joints and terminations. This ensures a reliable path for fault currents and is often the preferred method for indoor installations. Using the Cable Tray as Ground: In some cases, the metallic tray itself can serve as the EGC if it meets specific conductivity, cross-sectional area, and mechanical strength requirements outlined in NEC Table 392.

60(A),. Steel or aluminum trays can be used as grounding conductors for circuits with appropriate fault protection ratings, but care must be taken to avoid corrosion, especially with aluminum trays in moist environments. Bonding Jumpers: Short bonding wires may be used to connect tray sections, ensuring electrical continuity across joints and fittings.

This prevents interruptions in the grounding path and maintains safety under fault conditions.

Best Practices

Use compatible materials to prevent corrosion (e.g., insulated copper wire with tin or zinc-plated connectors for aluminum trays),. Ensure grounding connections are continuous and mechanically secure to withstand magnetic forces during fault currents. Regularly inspect and maintain grounding connections to ensure ongoing safety and compliance.

Conclusion

For indoor cable trays, grounding is required for safety, either by running a dedicated grounding wire along the tray or by using the tray itself as the grounding conductor if it meets NEC specifications. Proper installation, bonding, and maintenance are critical to ensure a safe and reliable electrical system.