One Bond Per Generator. Most Job Sites Have Two.

Monday, 6:40 a.m. My phone buzzes. It’s a foreman I know, and he’s already mad.

“Every GFCI on the temp panel trips the second we load the generator. We changed three of them. Still trips. The rental company says their set is fine.”

I drove out with a multimeter and a thermos. Forty-five minutes later the “broken” generator was running the whole site. Nothing was broken. The generator had its neutral bonded to its frame — exactly like the rental company intended. And the site’s temp panel had its neutral bonded too — exactly like the electrician intended. Two bonds. One system. That’s the whole story, and it cost that crew half a morning.

Here’s the thing about the neutral-ground bond: it’s a two-dollar piece of copper that decides whether your breakers behave. Almost nobody checks it. Almost everybody should.

Quick version for the non-electricians: your generator makes power on the hot wires, and the neutral is the road back. The “bond” is a jumper that ties that neutral to the generator’s frame and to ground. One bond in the whole system gives fault current a clean road home, so breakers trip when they should. Two bonds give current two roads, and some of it wanders down the ground wire. Zero bonds means a fault to the frame just sits there, waiting for someone to touch it.

Customers ask me about this constantly. Here are the three questions I hear most, with the honest answers.

“Bonded or floating — which one is right?”

Both. Depends on where the generator sits in the system.

The rule is stupidly simple: exactly one neutral-ground bond per electrical system. Not zero. Not two. One.

If your portable generator is running extension cords straight off its own receptacles — tools plugged into the set, nothing else — then the bond belongs at the generator. The frame is bonded, a fault to the frame has a path, the breaker sees it. That’s also why job-site practice leans this way: a bonded frame is what keeps a nicked cord from turning a steel generator into a surprise.

But the moment that generator feeds a building panel — a house, a shop, a site office with its own distribution board — the panel already has a bond. Put a second one in the generator and you’ve built the two-bond trap from my Monday morning story. For permanently installed standby sets it’s the same logic with fancier words. If the transfer switch switches the neutral (a four-pole, switched-neutral ATS), the generator is its own little system and the bond lives at the generator. If the transfer switch leaves the neutral solid straight through, the generator is not a separate system, and the single bond stays at the service entrance — the generator’s neutral floats. The transfer switch you choose is what decides this, which is one more reason to pick it deliberately instead of grabbing whatever’s in stock.

I watched a rental-yard tech do the right thing once. Every set that left his yard got its bond jumper pulled and tagged, because his sets fed panels that were already bonded. Then one Monday the site electrician — a careful guy, did everything by the book — bonded his temp panel too. Wait, that’s the same story as the opening. Different Monday, same two bonds. The jumper had been reinstalled by the previous renter “because the last site needed it.” Nobody wrote it down. That’s always the failure: not the copper, the communication.

My old mentor and I fight about this every year. He bonds everything that stands still long enough. “A bonded frame never killed anyone,” he says. He’s not wrong about the frame part. He’s wrong about the second bond, and I tell him so, and he tells me I’m overthinking it, and then we go look at a tripping GFCI together and he quietly pulls the jumper. Every year.

The GFCI Isn’t Broken. It’s Testifying.

That’s the second question I always get: “Why does the generator trip every GFCI on the site?” Nine times out of ten, it’s the two-bond problem wearing a costume.

A GFCI is a suspicious little device. It watches current going out on the hot wire and coming back on the neutral, and if even a few milliamps go missing, it trips. With two neutral-ground bonds, neutral current splits: some of it takes the ground wire home. The GFCI sees current leaving that never comes back on its neutral, and does exactly what it was built to do. The GFCI isn’t broken. It’s testifying.

The fix isn’t a new GFCI. I watched a guy learn this the expensive way at a food-truck festival on a Friday night — three trucks, music, a crowd, and every GFCI on the string popping every ten minutes. The previous electrician’s “fix” had been swapping GFCIs for plain outlets. Don’t do that. Ever. The protection was the only thing telling the truth on that site. The real fix took four minutes: open the generator’s connection box, find the bond jumper between the neutral stud and the frame lug, lift it, tag it, write down why. The panel already owned the single bond. Quiet night after that.

Fair warning, because honesty matters here: not every GFCI trip is a bond problem. Wet cords, nicked insulation, a heater with a tired element — those trip GFCIs too, and construction sites are full of all three. Check the bond first anyway. It’s a five-minute check with a meter, and it’s the cheapest suspect to eliminate.

On bigger sets you’ll see subtler versions of the same disease: ground-fault relays seeing phantom faults, neutral current showing up on the grounding conductor, voltage-to-ground readings that make no sense. Same root. Two roads home. And if you want the full picture on grounding a generator properly, that’s the companion piece to this one.

“How do I check what mine actually has?”

Third question, and the most useful one. Set off. Locked out. Disconnected from any panel or load — this matters, because a connected panel’s bond will fool your meter. Then the whole test is four steps:

1. Kill the set, lock it out, disconnect it from everything.
2. Meter on continuity (the beeper) or low ohms.
3. One probe on the neutral — the neutral terminal in the connection box, or the neutral pin of a receptacle. Other probe on the frame or ground lug.
4. Beep, or near-zero ohms: bonded. Open circuit: floating.

The jumper itself usually lives in the alternator terminal box — a short copper strap or a green wire between the neutral stud and the frame lug. Some sets have it on a removable link with a label. Rental fleets love wing nuts for it, because they move it more often than you’d think.

And check the wiring diagram pasted inside the connection-box lid. Look for the little ground symbol tied to the neutral line. Paper doesn’t lie the way memory does.

Here’s the one that still bothers me. Small clinic, permanently installed standby set, six years old. Somebody called me about “sixty volts on the frame, but everything works.” Everything did work — until you thought about what a ground fault would do. The installer had never made the bond. Floating neutral, no fault path, a breaker that would have watched a fault happen and done nothing. Six years. The fix was a ten-minute job and a label. The scary part wasn’t the fix. It was the six years.

One more warning, because this is where forum advice gets people hurt: don’t just pull a bond because someone online told you floating is “cleaner.” Know which side owns the single bond first. Pull the only bond and you’ve built the clinic’s problem on purpose. Single-phase or three-phase, portable or standby — the one-bond rule doesn’t care. It applies to all of them.

Write It on the Door

Whatever yours is — bonded or floating — write it on the inside of the connection-box door with a paint marker. Bonded or floating, date, your initials. The next person who opens that box, maybe at 6:40 on a Monday morning, will not have to guess. The copper is two dollars. The confusion it causes is worth two thousand. A label kills the confusion for about thirty seconds of work.

So next time you’re standing in front of a set with a meter in your hand anyway — during the load-bank run, say — take the extra minute. Beep or no beep. One bond, in the right place, written on the door. Your GFCIs will thank you by staying quiet, which is the only thanks a GFCI ever gives.

Not sure where the bond belongs on your setup? Talk to us — tell us whether your set feeds a panel or runs standalone, and we’ll point you at the right answer.