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The power in my house just went out for maybe 15-30 seconds. When the power came back on, one of my AFCI breakers was tripped. Thing is, I can't get it to stay back on. Every time I turn it back on, it trips after about 45 seconds. I went upstairs and unplugged everything from the outlets in the bedroom and turned off the switches, but it keeps on happening. I tested the circuit with the test button and it worked, but the breaker keeps tripping. Any idea what could be going on?

EDIT Added picture of breaker

Breaker

Solved

Well it's what I expected - the breaker was bad. Hooked up the circuit that was on it to another AFCI in the panel and it worked fine. Hooked up a good circuit to the bad breaker and it still tripped. POS AFCI breakers...

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What model AFCI? Does it have indicator lights to narrow down the cause? –  Bryce Mar 28 at 22:14
    
When I flip the breaker back on, neither LED comes on. According to w3.usa.siemens.com/powerdistribution/us/en/product-portfolio/… this would mean overcurrent fault, but I fail to see how that's possible as nothing is plugged in or on. –  2 Left Thumbs Mar 29 at 14:26
    
Use an ammeter to measure the current on the circuit. If it's the thermal protection, a delay wouldn't be that unusual if the current is close to the breakers trip point. –  Tester101 Mar 29 at 19:19

2 Answers 2

up vote 2 down vote accepted

If you've disconnected everything from the circuit there are only two causes I can think of - either the breaker is bad, or there is a legitimate arc occurring and the breaker is doing its job and possibly preventing a fire.

If you are comfortable opening your breaker panel, you could try replacing the breaker with a new breaker. If it still trips, I think that's a pretty definitive sign that there is an arc occurring. At this point, you probably want to call a licensed electrician to come diagnose and solve the issue. It could be a bad connection or a damaged wire.

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Yah, I don't mind running wire, but I really don't like the breaker panel. I figured that's probably the scenarios, but I can't figure out why the breaker keeps working (for 45 seconds) or how an arc would have shown up, suspiciously after a power blink, especially when there's nothing pluged in/turned on –  2 Left Thumbs Mar 28 at 23:43
    
Well the circuit breaker will also provide thermal and short circuit protection, so the delay could be related to the thermal protection, but that doesn't make much sense with zero load. Arcs can occur without load (hot to ground, hot to neutral). It's possible there was a surge along with the outage that could have caused this, or at least have worsened an existing condition to the point it is now a fault. –  Steven Mar 29 at 0:48
    
There's no proof here that load is at zero, just an OP statement that everything was unplugged. Something could have been missed. –  Bryce Mar 29 at 7:49
    
It's odd that it takes ~45-60 seconds to trip. You'd think that if there was a short/arc that it'd happen nearly instantaneously of turning the power back on. @Bryce I guess in theory I could have missed something, but these are non-cluttered rooms so it's pretty easy to tell if something is plugged in or not. The only thing that isn't unplugged is the lights/fan and neither of them are on nor were they on when the power went out. –  2 Left Thumbs Mar 29 at 13:54

Here is a sequence of a steps that could narrow this down. Follow this chart as long as you are comfortable, then skip to step #7:

  1. Check indicator lights on the AFCI, to determine the type of fault: ground, arcing, or overcurrent.
  2. Power cycle the main, thus "rebooting" the computer in the AFCI.
  3. Double double check for loads on this circuit. Perhaps remove any CFL's or smokes (as electronic devices they can create fake arcs on the circuit, if detective).
  4. Disconnect the black load wire from the AFCI, thus eliminating the circuit behind it from the equation.
  5. Swap this AFCI with another AFCI.
  6. Using a multimeter, and care, measure the actual 'on' current. A clamp type meter can be rented and is reasonably safe to use. A typical multimeter requires interrupting the black hot wire.
  7. Call in a professional electrician.

The test button on the AFCI tests the arc detection, not the circuit.

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