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I was wiring a ceiling fan in my new home, and I am not used to working with some of the newer electrical devices. I know very little about AFCI breakers, however I think I was somehow able to trip it when absolutely no power was on the line I was working with.

Both switches were off, for Black and Red. They tested dead. Just because I am a careful guy I tested neutral and ground for voltage as well and they were dead. I also tested continuity between ground and neutral and infinite resistance between neutral and colored wires as well as ground and colored wires. Everything is safe.

I was fishing the Black, Red, White and Neutral wires through the bracket when they all seemed to have made contact with the bracket at the same time. Immediately after this happened the lights went dead in the bedroom. The bedroom and smoke detectors were the only things on this circuit and their was only three lights on at the time.

I went to the breaker box to see the AFCI breaker in the middle tripped position, I turned it off, then back on and the ARC FAULT light as well as the GRND light came on. The breaker stayed on and it never happened again.

Does the AFCI breaker somehow test for a bad ground? Do you think somehow I triggered a bad ground fault when I accidentally touched all the wires to the bracket?

EDIT: So an AFCI breaker does have a neutral to the neutral block, and I imagine so that it can detect ground faults. Is it possible that the AFCI ground fault protection is so sensitive that I had a static shock that triggered it? I did get static shocked on my way into the bedroom earlier that morning. Static discharges from your body typically are only a few milliamps, is that enough to trip an AFCI breaker?

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  • Were you working on a 3-way switch circuit with the circuit breaker on?
    – shirlock homes
    Commented Dec 16, 2012 at 10:41
  • @shirlockhomes No. There was one two way that I wired for the light and one two way that was wired for the fan in a double gang box.
    – maple_shaft
    Commented Dec 16, 2012 at 11:50
  • I must be missing something or not understanding the question. Was the power off at the panel when this happened? I'm confused on how a breaker can trip if there is no power on that circuit.
    – shirlock homes
    Commented Dec 16, 2012 at 12:39
  • I read this to say the power was on at the panel, he isolated his work with the wall switches, thus the otherwise excessive testing. AFCIs should not be that sensitive, they must tolerate normal arcs from switches, plugging appliances in and out, motor brushes, etc. Something is not adding up, but I don't know what.
    – bcworkz
    Commented Dec 16, 2012 at 21:49
  • @bcworkz Maybe there is no definitive answer, because I don't know how to be more specific than I already was.
    – maple_shaft
    Commented Dec 17, 2012 at 4:04

2 Answers 2

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The AFCI worked as designed. It detected some small arc within the wiring and shut the circuit down. An AFCI has three detection modes: overcurrent, arcing and ground fault. Even a small amount of current imbalance will set the thing off. Be happy.

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If the neutral wire touches the ground wire, that will also cause the arc-fault to trip, every time. Which is probably what happened here.

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