Diagnosing AFCI breaker that trips at same time every day (with no load)

[less4success]

(This is with a new electrical panel and breakers from ~2016. I'm leaving the breaker off for now, in case there is actually an electrical problem that could cause a fire.)

I have a circuit in my house and the AFCI breaker has been tripping at roughly the same time everyday (between 5:30 and 6pm). Most recently, nothing was plugged in, and none of the light switches were on, so I don't think it's related to any fixtures/devices.

Any thoughts on how to diagnose?

Unfortunately, my breaker doesn't have an LED to indicate the reason it tripped (brand: Eaton). I assume if this was actually due to an arc fault, it might happen at the same temperature+humidity, but we've had both cold/rainy and warm/sunny weather and it still trips between 5:30pm and 6pm. Note that if I reset the breaker, it trips again... but only until around 6pm, at which point everything's fine until 5:30 the next day. I assume a malfunction would happen either constantly or at the same interval, regardless of the time of day.

My best guess is some sort of interference. I've heard tales of Eaton AFCIs tripping due to HAM radio. I have no idea how credible these stories are, although one claimed to have worked with Eaton to solve a real problem.

My plan is to replace the breaker with a new AFCI (actually AFCI/GFCI combo, since that's all my hardware store carries), and see if the problem recurs. If it does, I think this new breaker will have an LED to indicate the trip code, so at least I can then narrow down my search to e.g. actual arcing/loose connections.

Edit to add: this is a recent issue. I had not had any issues on this circuit since moving in.

[uniwelder]

I'm not an electrical expert, so I'd like to hear what others suggest--- posting to follow.

As a first step, before buying anything, do you have another AFCI circuit in the house?  If its close to the suspected bad breaker, you could just swap wires between them, and then see what happens between 5:30-6:00.

[less4success]

As a first step, before buying anything, do you have another AFCI circuit in the house?  If its close to the suspected bad breaker, you could just swap wires between them, and then see what happens between 5:30-6:00.

Good suggestion! I had considered swapping two breakers, but swapping two wires would be much simpler (edit: easier). There's an identical breaker maybe halfway down that might work.

If the problem circuit trips at 5:30pm again, I'll assume there's a real problem and maybe try putting in a breaker that emits a diagnostic code (and watching carefully!). If the other circuit trips, then it would seem like probably a faulty breaker. If neither trips... I'll probably replace the original breaker and un-swap the wires.

[uniwelder]

As a first step, before buying anything, do you have another AFCI circuit in the house?  If its close to the suspected bad breaker, you could just swap wires between them, and then see what happens between 5:30-6:00.

Good suggestion! I had considered swapping two breakers, but swapping two wires would be much simpler. There's an identical breaker maybe halfway down that might work.

If the problem circuit trips at 5:30pm again, I'll assume there's a real problem and maybe try putting in a breaker that emits a diagnostic code (and watching carefully!). If the other circuit trips, then it would seem like probably a faulty breaker. If neither trips... I'll probably replace the original breaker and un-swap the wires.

Not that its much simpler, I just thought the lesser number of changes you make, the better it would be to diagnose.  By swapping the breakers, you might introduce some change like the way its contacting the bus bar.

[less4success]

Good points. By "simpler" I really meant "easier".

[BC_Goldman]

As someone who is also dealing with nuisance tripping, you have my sympathy.

Your case is interesting since I thought I had read that Arc Faults weren't supposed to trip unless there are more than five amps on the circuit.

[solon]

I had a similar issue recently. AFCI, tripped twice in one week. Both times I flipped it back on and it stayed on (for a few days anyway, until it tripped again). I was worried about a fire so I called an electrician to take a look.

He told me that if there really was an arc fault, the breaker would immediately switch off every time you turned it back on. You wouldn't be able to keep it on. Because it was days between the two trips, and days since the second trip without tripping a third time, there can't be an arc fault. He replaced the breaker for me and I haven't had any problems since then (about two months).

Conclusion: it was a faulty breaker.

[sonofsven]

Switching to the other breaker would be the first step, to try to isolate if it's a breaker problem or a wiring/device issue. This will likely solve the problem as these breakers are somewhat notorious for acting up.
Next would be to check the wiring at each device (outlet) on the circuit, starting at the farthest downstream and working back
If the wiring is routed to the next outlet box through the device you might want to join the wires with wire nuts and add short pigtails to the outlet. This way a bad outlet or bad connection to the outlet doesn't take out the the downstream outlets.

[less4success]

It's discouraging to hear how often these $50 breakers go bad for no apparent reason. I assume they won't honor the warranty if I'm not the original purchaser, but maybe I'll call and ask...

Your case is interesting since I thought I had read that Arc Faults weren't supposed to trip unless there are more than five amps on the circuit.

That reinforces my suspicion that it is simply a faulty breaker. From the documentation, the breaker can trip due to many difference reasons, including things like "self-test failure". Of course, the breaker has no way of indicating the reason it tripped... which is incredibly annoying...

Switching to the other breaker would be the first step, to try to isolate if it's a breaker problem or a wiring/device issue. This will likely solve the problem as these breakers are somewhat notorious for acting up.
Next would be to check the wiring at each device (outlet) on the circuit, starting at the farthest downstream and working back
If the wiring is routed to the next outlet box through the device you might want to join the wires with wire nuts and add short pigtails to the outlet. This way a bad outlet or bad connection to the outlet doesn't take out the the downstream outlets.

Thanks! This info will be handy if the problem ends up actually being something other than the breaker.

[Syonyk]

I hate to say it, but step one of troubleshooting a nuisance-tripping GFCI outlet/breaker, or AFCI, should be to replace the damned thing and see if the problem comes back.  They go bad irritatingly often.  I've replaced an outside GFCI we were using for EV charging with a non-GFCI just because I chewed through two GFCIs in about a year and a half.  They seemingly don't like sustained high current.

[less4success]

I wasn't able to simply swap wires because all the wires had been cut to the minimum length possible.

Instead, I grudgingly replaced the suspect breaker with a new one from the same manufacturer. This new model has an LED that displays trip codes, so if it trips in the future, I'll at least know why. If it goes bad, it will be under warranty (and I have proof of purchase).

Torquing the screws to spec was a little tricky because all the screws were difficult to reach with my tools.

[less4success]

The new AFCI+GFCI breaker hasn't tripped since I installed it, so given that the old one appeared to have good connections, I'm assuming it just failed.

Here's hoping all the other ones in my panel don't start dying next...

Thanks, everyone!

Edit: It was a gen 4 Eaton type BR breaker, for the record.

[lutorm]

We've had two Eaton CH breakers (one AFCI and one AFCI/GFCI combination) go bad in maybe 2 years. They were both nuisance tripping, I don't remember exactly what the AFCI one did, but the latter one flashed its "self test failure" when reset. Eaton replaced both, no questions asked. I did have receipts, but for the last one I just contacted the person who mailed out the first replacement and he just sent one, I didn't even have to mail the old one back.