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I have a very unusual set of electrical issues that have proven difficult to troubleshoot.

I live in a newly constructed house. Each bedroom has AFCI breakers.

In the past 3 years living there, the AFCI breaker to my bedroom has tripped about a dozen times. All occur sometime in the middle of the night. Each time, resetting the breaker has resolved the problem. Sometimes the breaker will trip when the 1000W Lutron Dummer is turned on. Sometimes it trips while we are asleep.

I have noticed that when the breaker trips the "Arc" light is not activated which I believe means the AFCI breaker tripped due to a ground fault?

Interestingly, almost every time this has occured, two GFCI outlets, one in our kitchen and one in our garage has also tripped, but with much less frequency. In our case this has happened 4 times in 3 years (1-2 times a year). Each GFCI outlet is on a different circuit in this case. The GFCI outlets do not trip if the AFCI breaker doesn't trip.

Also, one GFCI circuit is in a different panel than the other one.

I could replace the AFCI breaker and the 2 offending outlets. Is there something else I should be looking for?

The only thing that I can think of that would cause this problem is something temperature related or perhaps some kind of surge? is that possible?

Things I have heard that can cause an AFCI breaker to trip:

  1. Stack of AFCI breakers in the electrical panel over heating (I have 4 in a row, with Master Bedroom in the middle
  2. Dimmer (something about Lutron)
  3. Pinched or stapled electrical wire(would this just cause it to trip consistently though)
  4. Charging electrical gizmos

Things I have heard that can cause a GFCI breaker to trip

  1. Variations in supply voltage
  2. Unbalanced, intermitant loads (I don't have any)
  3. Cheap surge protectors

Things I have heard that can cause an AFCI and a GFCI breaker to trip

  1. Cheap surge protectors (I have a few surge protectors on each AFCI and GFCI outlets that are tripping). I'm not sure I'd consider them "cheap".

Could any of this be upstream from me?

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Do you have an attic fan or anything like that? –  Steven Sep 22 '12 at 1:47
    
No attic fan. I do have electric radiant floor heating that cycles on and off, but that's in the bathroom on a different circuit. –  Omar Shahine Sep 22 '12 at 2:18
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It's not a bad idea to buy one name brand AFCI and GFCI from a place with a generous return policy. Swap them in and see if it solves the problem. –  Jay Bazuzi Sep 22 '12 at 6:52
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This is a tough question to answer without actually walking through the house, there could be far too many variables involved. At the very least a detailed circuit map; including everything plugged in, might help in locating the issue. If you have a UPS for your computer, most of them will log data and may be able to inform you of any spikes (at least on that circuit, though if it's a spike or imbalance system wide you may pick it up). –  Tester101 Sep 22 '12 at 12:56
    
Latest theory. Each AFCI and GFCI outlet that "trips" has a surge protector on it. I read somewhere that a surge on my grid could cause each of these surge protectors to handle the surge, which would cause the AFCI and GFCI to sense that there is a power imbalance hence tripping the breaker. I also read that AFCIs are much more sensitive to ground faults which is what it would sense if there is a surge that the surge protectors are having. I am removing all surge protectors from the house plugged into AFCI/GFCI to check. –  Omar Shahine Sep 23 '12 at 16:41

5 Answers 5

My initial thought was poor a ground somewhere in the circuit causing disparity in the loading and leading to a trip, i.e. a loose ground wire at the panel or receptacle.

See this link for some relevant answers. It will give you a start in the right direction.

http://www.thecircuitdetective.com/afci_circuit_breakers.htm

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Make sure your answer is still useful if the link goes bad. See how to answer –  BMitch Oct 21 '12 at 21:05
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A GFCI measures current between hot and neutral and wouldn't trip solely due to a broken ground (a ground fault doesn't mean the ground is broken). Arc faults detect arcing, so unless the ground is energized, loose and arching, I really don't think it would trip it. –  Steven Oct 22 '12 at 1:58

The problem could be "upstream". These breakers can be tripped by noise, such as voltages induced by radio-frequency interference.

Triac-based dimmers abruptly turn power on and off 120 times a second, causing switching noise which has high frequency components.

"Mystery trippings" of GFCI's are not uncommon. To get to the root cause, you would need special equipment, knowledge and time on your hands. For instance a digital oscilloscope to capture a trace of the outlet's line voltage leading up to the event. If a spike, or some strange noise is recorded, then that explains the tripping. But, of course, you still don't know where it came from or what, if anything, can be done about it.

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Some surge protectors work by "redirecting" surges to the equipment ground, which is pretty much the definition of a ground fault. In this case, it's definitely possible that surge suppressors could be tripping GFCI receptacles/breakers (given a large enough surge).

As for the AFCIs... When electrical contacts separate, they often create an arc between the contacts. This arc spans the gap until the contacts are too far apart, and the arc can no longer be sustained. It's possible (in theory) that the GFCI tripping could create a large enough arc, for long enough to cause the AFCI to trip. It's not likely that a properly functioning GFCI would do this, but if the GFCI was old and worn it could be opening the contacts slow enough that a detectable arc is being produced.

Determining if the GFCI tripping is causing the AFCI to trip, is a simple test. Simply press the test button on the GFCI. If the AFCI trips, you'll have figured out half the problem. If the ACFI does not trip, you could repeat the test using a receptacle tester with a GFCI test function.

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If it's determined that the GFCI is causing the AFCI breaker to trip, replacing the GFCI receptacle may resolve that part of the issue.

Figuring out if the surge suppressor is tripping the GFCI, is a more difficult proposition. It will likely require you to monitor the supply voltage over some time, to identify and document possible surges.

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Interestingly enough, I have removed all surge protectors from every AFCI and GFCI protected circuit and have not had any tripping since I wrote this in September. –  Omar Shahine Apr 13 '13 at 23:12

Tighten all the screws that hold wires. A slightly loose connection can cause trouble that happens at different times.

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I've heard a vacuum that is full will strain the motor causing a greater arc at the brushes/stator. This will trip an AFCI.

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I suspect they aren't running the vacuum while sleeping at night. –  BMitch Sep 27 '13 at 18:58

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