Grounding in cable trays

Yes, metallic cable trays must be properly grounded to ensure electrical safety, system reliability, and compliance with NEC and other standards.

Grounding Requirements

All metallic cable trays are required to be grounded according to NEC Article 250.96, regardless of whether the tray itself serves as an equipment grounding conductor (EGC) or not . Grounding ensures that in the event of a fault, the tray does not become energized, preventing electric shocks, equipment damage, or fire hazards . Proper grounding also maintains electrical continuity across tray sections and connections, which is critical for safety and inspection compliance .

Bonding Practices

Cable trays are bonded together through bolting, splice plates, clamps, and bonding jumpers where gaps exist . Mechanical connections alone may not provide reliable electrical continuity, so bonding jumpers are often used to maintain an effective grounding path . For installations with multi-conductor cables, each cable's EGC should be bonded to the tray sections, either at every section or at alternate sections, to ensure fault current paths are maintained . Bare copper conductors should not be used in aluminum trays to avoid electrolytic corrosion; insulated conductors with exposed bonding points are preferred .

Tray as Equipment Grounding Conductor

In qualifying facilities, the cable tray itself can serve as the EGC if it meets minimum cross-sectional area requirements and is electrically continuous . Steel trays are limited to circuits with ground-fault protection up to 600 amperes, while aluminum trays can handle up to 2,000 amperes . Where the tray is not used as the EGC, a separate grounding conductor should be installed inside or attached to the tray, sized according to NEC tables .

Special Considerations

• Power circuits: Cable trays must be bonded back to the power source and connected to all conduit or raceways in the system .
• Signal and communication circuits: Even if low-energy, trays should be grounded for lightning protection, EMI, and noise reduction .
• Mechanical integrity: All tray sections should be mechanically tight and electrically continuous to prevent interruptions in the grounding path .

Conclusion

Proper grounding and bonding of cable trays are mandatory for safety, compliance, and operational reliability. Metallic trays must be electrically continuous, securely bonded, and connected to the building's grounding system. Failure to ground trays correctly can result in shock hazards, equipment malfunction, and code violations .