Missing connection of cable tray jumper wire

A missing cable tray jumper wire can compromise electrical continuity and safety, especially across expansion joints, painted trays, or adjustable splices, and should be addressed according to installation standards.

Importance of Cable Tray Jumpers

Cable tray jumper wires, also called bonding jumpers, ensure electrical continuity and grounding across cable tray sections. They are critical when: The tray has expansion joints that allow movement, requiring a flexible connection to maintain continuity. The tray is painted or powder-coated, as coatings block electrical contact between metal parts.

The system is in a high-vibration environment, where bolted connections alone may loosen over time. Without a jumper in these situations, the tray may fail inspections, and electrical faults could pose safety hazards.

When Jumpers May Not Be Required

For standard rigid metallic splice plates in unpainted, stationary aluminum or steel trays, bonding jumpers are often not necessary. Properly bolted splice plates can provide sufficient electrical continuity if: The metal surfaces are clean and free of paint or coating. Bolts are tight, and serrated washers or star washers are used to ensure good contact.

The splice plate meets the tray's grounding rating and UL classification. In these cases, adding a jumper may not improve safety and could be considered unnecessary labor and material use.

Proper Installation Practices

If a jumper is required, follow these guidelines: Connect to the tray channel, not the splice plate bolts. Use flexible copper wire, typically 2 AWG soft-drawn tin-plated stranded copper, with flame-retardant insulation. Ensure the jumper has enough slack to accommodate tray movement at expansion joints.

Remove coatings at connection points to allow metal-to-metal contact. Verify connection resistance is below 0. 0003 ohms to ensure compliance and safety.

Additional Considerations

Avoid placing bare copper conductors in aluminum trays in moist environments to prevent electrolytic corrosion; use insulated conductors with proper connectors. For adjustable splices or expansion splices, jumpers are mandatory to maintain continuity. Regular inspection and maintenance are recommended to ensure jumpers remain secure and functional over time.

Conclusion

A missing cable tray jumper wire can compromise grounding and safety, particularly in painted, movable, or high-vibration tray systems. Evaluate whether your tray sections require jumpers based on tray type, coating, and movement, and install them following proper bonding practices to maintain electrical continuity and pass inspections.