Grounding should be installed at regular intervals along metallic cable trays to ensure safety, typically at each tray section or every few meters using bonding jumpers or clamps.

Importance of Grounding

Proper grounding of cable trays is essential to prevent electrical shocks, channel fault currents safely to the ground, and reduce electrical noise or interference in sensitive equipment . Metallic trays can serve as equipment grounding conductors (EGC) if they meet NEC requirements, but additional grounding conductors are often recommended for reliability .

Recommended Grounding Practices

• Bonding Between Tray Sections: Each tray section should be electrically bonded to adjacent sections using grounding clamps or flexible jumpers. This ensures continuity of the grounding path and prevents mechanical displacement of conductors under fault conditions .
• Spacing of Grounding Points: While the NEC does not mandate exact distances, best practice is to install grounding points at each tray section or every few meters to maintain a low-impedance path for fault currents .
• Conductor Selection: Use insulated conductors when bonding aluminum trays to avoid galvanic corrosion. For steel trays, bare or insulated copper conductors are acceptable, sized according to NEC Table 250-95 based on the highest fuse rating or breaker setting .
• Inspection: Grounding should be inspected before energizing the cables and after installation to ensure all sections are properly bonded and marked as suitable for grounding .

Additional Considerations

• Independent Grounding Lines: In critical installations such as rail systems, industrial facilities, or solar plants, independent grounding lines using braided copper or galvanized conductors may be implemented for added safety .
• Connection Methods: Use brass tray grounding terminals or tin/zinc-plated connectors to bond conductors to the tray, ensuring secure mechanical and electrical connections . By following these practices, grounding in cable trays provides a safe, reliable, and code-compliant electrical system, minimizing the risk of shock, fire, and equipment interference.