What is the proper length for a bonding jumper?

• A. As short as practical, but long enough to allow free movement of the equipment
• B. Long enough to reach the power source
• C. Exactly 12 inches
• D. At least one meter

Answer: (A)

Bonding jumpers are meant to keep two metal surfaces at the same electrical potential while still allowing the connected equipment to move or vibrate without stressing the bond. The best length is as short as practical, but long enough to allow free movement of the equipment. This keeps the impedance low and the bond reliable, while avoiding excess slack that could snag, wear, or interfere with operation.

Why this length works: keeping the jumper short reduces resistance and potential points of failure, which is important for maintaining a solid bonding path during vibration and movement. It also minimizes the chance of the wire being pulled or damaged. If you tried to lengthen it to reach a power source, that’s not the purpose of a bonding jumper—the bond should connect between the bonding points, not to the power supply. A fixed length like a specific inch or meter ignores the various mounting geometries you’ll encounter, which could either restrict movement or leave excessive slack.