How far should cable trays be grounded for safety

Cable trays should be grounded at each section or at regular intervals using grounding clamps or conductors to ensure electrical continuity and safety.General Grounding Requirements

Metallic cable trays must be grounded according to NEC Article 250.96 and NEC Article 392. This applies whether the tray is used as an equipment grounding conductor (EGC) or in addition to individual cable EGCs. Grounding ensures that fault currents are safely conducted to the main grounding system, preventing electric shock and equipment damage .

Recommended Grounding Intervals

• Each tray section or alternate sections: While the NEC does not mandate exact spacing, it is considered best practice to bond each cable tray section or at least every other section using grounding clamps .
• Flexible jumpers: When trays are used as grounding points, flexible jumpers with appropriate lugs should connect the tray sections to maintain electrical continuity .
• Critical installations: In industrial, rail, or solar power projects, independent grounding lines may be installed at specific intervals using braided copper or galvanized conductors for enhanced safety .

Additional Considerations

• Material compatibility: Avoid bare copper in aluminum trays to prevent electrolytic corrosion; use insulated conductors with insulation removed only at bonding points .
• Tray as EGC: Steel trays should not be used as EGCs for circuits with ground-fault protection above 600 A, and aluminum trays above 2000 A .
• Separation of power and signal cables: To reduce electromagnetic interference, power and signal cables should ideally be in separate trays or separated by barriers, following IEEE 518 guidelines .

Practical Tip

For most installations, grounding every tray section or at intervals of 10–20 feet is a common industry practice, ensuring mechanical stability and reliable fault current paths. Always verify grounding conductor sizing according to NEC tables to maintain compliance and safety . By following these practices, cable tray systems remain safe, electrically continuous, and compliant with regulatory standards.