What is the minimum gauge for a single item bonding conductor?

• A. #4 AWG or larger
• B. #6 AWG or larger
• C. #2 AWG or larger
• D. #1 AWG or larger

Answer: (B)

The main idea here is equipotential bonding for a single large item. A single item bonding conductor is used to connect one major piece of equipment to the building’s grounding system so that all parts of that item are at the same electrical potential as the rest of the site, reducing the risk of dangerous voltage differences during faults or fault clearance.

To do that safely, the conductor must be large enough to carry any fault current that could flow through it long enough for the protection to trip, and it must hold up to the environment and corrosion. In this context, the minimum size specified is copper #6 (or larger). That means #6 AWG is the smallest you can use for a single item bonding conductor, and you may use larger sizes if desired for additional margin. Using a smaller gauge would not provide a reliable low-impedance path for fault currents, which is why #6 is the threshold. Larger gauges, like #4 or even thicker, are acceptable but not required by the minimum rule.