The breaker is a GFCI breaker (ground fault) or an AFCI (arc fault) breaker?

Hi, thanks for responding. Since it's for my bedroom, I'm guessing it's an arc fault breaker? Anyway, here's a pic of it. The one that's the culprit is labeled "G", although the one right above it is just like it. I'll try and educate myself and find out what an arc fault breaker is for.

Arc faults are touchy. I've tripped them plugging in a central vac power head.

I would guess that the transfer switch kicking in and out is enough to trip it, but I don't know much about arc faults.

Are there other arc faults that are powered when the generator's running? If so, but only one's tripping, maybe it's faulty...but if it doesn't trip wh

en the regular power's on, something else may be happening.

A lot of jobsite/portable generators produce "dirty" power, full of spikes etc, which is why they're not usually good for computers and other delicate devices. That may be part of the issue.

Unfortunately, I only have one circuit that's powered by the generator that has an arc fault breaker. And of course, all of the other circuits behave just fine. What are arc fault breakers for?

They detect arcs in the wiring and shut off the power. An arc can generate sufficient heat to cause a fire without enough current flowing to trip the normal overcurrent part of the breaker. They have been phased in to the code over the past five years or so. Originally, only bedroom outlets needed to be so protected, later code requires them on all living space (other than kitchens and bathrooms which require GFCI protection).

As pointed out, some of the early ones are a bit twitchy. I know that a lot of the nuisance trips went away with later mods of the GE AFCI's. I don't know about square D on this.

Frankly, mechanical transfer switches like you have, aren't really reliable ways to switch things under load.

While it's somewhat difficult to think up a scenario that would easily cause this, there's a couple things I would check.

First I'd make sure that somebody didn't do some creative wiring and tie the two neutrals from the that breaker, and the one above it (which appears you are not transferring) and ran a multiwire branch circuit.

The other would be to see if somebody tied a neutral from another branch circuit, to this circuit, in a junction box downstream somewhere. Lift the neutral off the breaker and measure between the neutral wire and ground with an ohm meter - should be open. If not it's tied to another neutral somewhere.

Also, are you using any type of home automation for controlling lights and outlets?

The switching back to line power is not synchronized to the line power from the POCO.

Tripping an arc fault is not all that surprising.

Weird things can happen at a hot-hot crossover.

Hot from a separate supply (your generator) to hot from he POCO (when it comes back on), especially under load.

A newer AFCI might be a little less sensitive.

It is one of the reasons for some time lag between disconnecting a generator and reconnecting to the POCO.

It needs to be long enough to look like a clean 'OFF' before going back to the POCO.

In very large installations it can take a few seconds of 'OFF' time (especially with larger or more sensitive loads).

That makes sense. Do the automated transfer switches allow for that delay time? Anything in the house that's really critical ought to be on an UPS in addition, to allow for a smoother changeover.

I wonder if the switch is momentarily connecting both the generator and the line at the same time. This would definitely cause an AFCI to trip, I think.

The OP provided a link to the transfer switch he is using. He is NOT using an automatic transfer switch or a manual whole house transfer switch. He is using a 10 circuit manual transfer switch that allows for switching individual branch circuits between "line" and "generator".

As he explained: "When my transfer switch is set to "gen" , my generator is on and all of a sudden, the power comes back, my breaker trips."

From the way I understand it, he is saying that no changes have been made on the transfer switch and one particular AFCI breaker in the panel trips simply because his power has been restored.

While I can certainly see an AFCI tripping during a change from generator to line, or the protection device being overly sensitive, there appears to be something else going on here. Since the hot is switched to the generator, it would make sense to begin troubleshooting by suspecting that the problem is occurring on the neutral side.

What does POCO mean? I'm guessing it essentially means electricity from my utility company? I did a google search, but everyone talking about it just talked about it and I couldn't find an explanation.

Maybe it was simply something obvious I did wrong. When I get home, I'll take off the panel and see if I did anything crazy for that one breaker. I'll report back with what I find. Thanks, guys.

Weedmeister's comment just made me think of another possibility - current leakage between the line and generator hots in the "G" transfer switch, or it's associate wiring.

yosemitebill, I'll definitely look at how the neutral is set up for this breaker. And yes, it's a manual transfer switch I have.

ronnatalie, you say transfer switches aren't reliable. Would you recommend a interlock setup instead? Why are manual transfer switches unreliable in your book?

Make sure the generator ground-neutral bond is REMOVED.

Most generators come bonded for free standing use with a ground electrode.

When powering a residential main panel the ground-neutral bond is IN THE PANEL and should not be duplicated in the generator.

While the generator supplies two hots and a neutral, is is getting ground from the panel.

NOT the other way around (generator grounding the panel).

And POCO is POwer COmpany.

Hello bigyellow:

Did you ever determine what the problem was? I'm having the exact same trouble as you were on 3 out of the 6 that wired to my reliance transfer switch. All 3 are AFCI breakers.

Thank you.

Make sure you've properly wired the AFCI breakers and the transfer switch especially with regard to the neutrals.

HU - 997794006 - I`m having the same issue with my new Reliance A310A TS. AFCI breaker trips when testing and line power still available. Wiring is all correct just the 1 AFCI trips during live switch over. Would appreciate any info you gained to solve the issue? Thanks

These manual transfer switches use the breaker in the transfer switch when using generator power. Those breakers are not (can not be) AFCI because there is a single neutral from the transfer switch which lands on the neutral bar of the main panel. An AFCI breaker has the neutral coming back from the load and then in normal operation out of the breaker to the neutral bar. Because of this, you can't have AFCI's in a load side transfer switch because you would have to switch the neutrals and the hots. An AFCI needs power to trip, so when your utility power is off, the circuit works because the hot is fed by the generator and the neutral flows from the load to the AFCI breaker in the panel and then to the neutral bar. When utility power is restored, the AFCI is powered and it detects a fault condition because it sees a major imbalance between hot (which it can't detect because it is coming from the generator) and neutral. It is now able to trip since it is powered, and it does.

Huh, no. The AFCI cares nothing whatsoever about the line neutral (other than it needs one to power its internal logic. What you do have to do is bring the load neutral over as well as the load hot.

I had the same issue but to fix I turn off my main power before I switch to "Gen" on the manual transfer switch even though you shouldn't u have to when using the manual transfer switch. When I see my neighbors have lights then I shut off the generator and unplug the cord from inlet box then turn the main back on . My arc breakers don't trip anymore. My general is bonded to frame also.