Cable tray jumper wire size

Cable tray jumper wires are typically sized based on the largest ungrounded conductor in the tray or per NEC Table 250. 102(C)(1), with braided copper jumpers commonly used for flexibility and reliability.

Jumper Wire Sizing

The size of a cable tray bonding jumper depends on the largest ungrounded supply conductor in the tray.

According to NE

C Section 250. 102(C)(2), if multiple raceways or cables are paralleled, the jumper can be sized either individually for each raceway or as a single jumper based on the sum of the circular mil areas of the largest conductors in each set. For very large conductors exceeding 1100 kcmil copper or 1750 kcmil aluminum, the jumper must be at least 12.

5% of the area of the largest ungrounded conductors.

Jumper Type and Material

Braided copper jumpers are preferred because they are flexible and can accommodate movement in expansion joints without breaking. Standard jumpers, such as Snap Track bonding jumpers, are often 36 inches long and green in color, but custom lengths are available. The wire must be UL-listed or approved for grounding, not just any conductor.

Installation Considerations

Ensure tight bolting of splice plates; painted or powder-coated trays require jumpers because coatings block electrical continuity. Typically, a minimum of four bolts (two on each side) is recommended to maintain a reliable connection. For long cable tray runs, bonding jumpers may be installed every 50–100 feet to improve safety and reduce impedance.

Summary

To select the correct cable tray jumper wire size: Identify the largest ungrounded conductor in the tray.

Refer to NE

C Table 250. 102(C)(1) for the corresponding jumper size. Use braided copper jumpers for flexibility, especially at expansion joints or painted trays.

Ensure proper bolting and periodic bonding along the tray for safety and compliance. Following these guidelines ensures electrical continuity, safety, and NEC compliance in cable tray installations.