Should galvanized cable trays be fitted with jumper wires

Galvanized cable trays do not generally require jumper wires if standard bolted splice plates are used and properly installed, but jumpers may be needed in special conditions such as painted trays, expansion joints, or high-vibration areas.

Standard Installation

For standard galvanized steel cable trays with rigid, bolted side rail splice plates, bonding jumpers are not required. Properly installed splice plates provide sufficient electrical continuity to meet NEC Section 318-6(a) requirements, ensuring the cable tray system is electrically continuous and capable of safely conducting fault currents without additional jumpers . Tests on NEMA Class II aluminum and galvanized steel ladder trays have shown that standard bolted splice plates perform as well or better than copper bonding jumpers under fault conditions .

Situations Requiring Jumpers

While jumpers are not needed for standard, clean, and tightly bolted connections, certain conditions necessitate the use of flexible copper bonding jumpers:

• Painted or powder-coated trays: Coatings can block electrical continuity, preventing proper grounding .
• Expansion joints: Trays designed to move due to thermal expansion or contraction require flexible jumpers to maintain electrical continuity .
• High-vibration environments: Mechanical movement can loosen bolted connections, making jumpers necessary to ensure safety . In these cases, jumpers provide a low-impedance path to maintain grounding and prevent arcing or equipment failure.

Best Practices

• Ensure all bolted connections are tight and free of paint or corrosion.
• Use serrated nuts or star washers to penetrate oxidation layers and improve electrical contact .
• Verify that the tray meets NEC Table 392.60(A) requirements if it is intended to serve as the equipment grounding conductor (EGC), .
• For aluminum trays, avoid bare copper conductors to prevent electrolytic corrosion; use insulated conductors with proper bonding connections .

Summary

Galvanized cable trays typically do not require jumper wires when using standard, properly installed bolted splice plates. Jumpers are only necessary in special conditions such as painted surfaces, expansion joints, or high-vibration areas to ensure electrical continuity and compliance with safety standards . Proper installation and inspection are key to maintaining a safe and code-compliant grounding system.