Metallic cable trays must be electrically continuous, properly bonded, and connected to the building grounding system to safely conduct fault currents and prevent electrostatic hazards.

Electrical Continuity and Bonding

All metallic cable trays must maintain electrical continuity across sections, splices, and fittings. Mechanical connections alone may not always ensure reliable conductivity, so bonding jumpers are often required to bridge gaps and maintain a continuous grounding path . Each tray section should be mechanically tight and electrically continuous to prevent potential shock hazards or equipment damage .

Equipment Grounding Conductor (EGC) Requirements

Cable trays can serve as an Equipment Grounding Conductor (EGC) if they meet minimum cross-sectional area requirements for the side rails, based on the protective device rating (fuse or circuit breaker) of the circuit . If the tray's conductive area is insufficient, a separate EGC must be installed within the tray or alongside the cables . Non-metallic trays cannot serve as conductors, and wire mesh trays are generally not recommended as EGCs due to reduced current-carrying capacity when cut or modified .

NEC Compliance

According to the National Electrical Code (NEC):

• NEC 318-6(a) requires cable trays to be electrically continuous, even if mechanical continuity is not mandatory .
• NEC 250-51 specifies that the grounding path must be permanent, low-impedance, and capable of safely conducting fault currents .
• All metallic components enclosing electrical conductors must be bonded to limit voltage to ground and facilitate operation of overcurrent protective devices under fault conditions .

Best Practices

• Ensure all tray sections, fittings, and splices are mechanically tight and electrically bonded.
• Verify grounding conductor sizing according to NEC tables to handle potential fault currents .
• Use solid or ventilated trays for grounding purposes; avoid wire mesh trays unless a separate ground wire is installed .
• Maintain proper separation of power and data cables to reduce electromagnetic interference while ensuring grounding continuity .

Summary

For safe and code-compliant electrostatic connection of cable trays:

1. Use metallic trays with continuous electrical paths.
2. Bond all sections and fittings, using jumpers if necessary.
3. Ensure the tray or a separate EGC meets NEC sizing requirements.
4. Avoid relying on wire mesh trays alone for grounding.
5. Connect the tray system securely to the building's grounding network to safely conduct fault currents and prevent electrostatic hazards .