Bonding jumper

Grounding and bonding get used as one word on a job site, but they do different jobs. Grounding connects the system to the earth. Bonding ties metal parts to each other so none of them can float at a different voltage than its neighbor. A bonding jumper is the piece of wire or strap that does the tying. Get it wrong and the metal in your house can sit quietly energized instead of tripping a breaker.

The one that matters most is the main bonding jumper, covered by Section E3607.5 of the 2021 International Residential Code. It is unspliced, it lives inside the service enclosure, and it connects the neutral to the metal box and the equipment grounding wires. That bond gets made once. Past the service, every subpanel keeps neutral and ground on separate bars, which is why a detached casita or shop is fed with a four-wire feeder instead of three.

Equipment bonding jumpers are the second family, and they show up wherever metal could become energized. Gas piping is the common one. Pinal County states it plainly in its residential gas bulletin: any above-ground gas piping that can become energized has to be bonded to the electrical service electrode system, and a system containing CSST needs a jumper no smaller than 6 AWG copper, run no more than 75 feet.

For example, a Cave Creek custom home with a propane range gets both. The electrician makes the main bond in the service panel at rough-in. Then a 6 AWG copper jumper runs from the steel gas pipe past the second-stage regulator back to the ground at the service. Two jumpers, two purposes, and on most jobs two different trades. The main bond is an electrician's item all day. The gas jumper is the one that falls through the crack, because the plumber sets the pipe and the electrician lands the wire.