Troubleshoot 20amp GFI branch Circuit

Discussion in 'Electrical Forum discussion & Blog' started by Jean-Claude JC Lussier, Jul 21, 2014.

  1. Jean-Claude JC Lussier

    Jean-Claude JC Lussier New Member

    Messages:
    7
    Location:
    Manitoba
    Hello everybody,
    I am completely stumped. I am wiring a new bathroom in my basement, and everything seemed fine until yesterday. I have two recessed lights in my shower that I had temporarily wired to an existing switch in another room which worked fine. I have now added outlets to the rest of the room supplied from a 20 amp gfi breaker and now I have connected the lights to the new circuit. That's where the problem started. All the outlets test fine using an outlet tester but as soon as I flip the switch to the shower lights, the breaker trips. Once it even blew the dimmer switch. If I take the bulbs out of the fixtures the breaker doesn't trip. If I bypass the switch and wire the lights direct the breaker, the lights turn on and the breaker doesn't trip. I don't know what I did wrong or what to try next. Any help would be greatly appreciated.
    Thanks

    [​IMG]
  2. Reach4

    Reach4 Active Member

    Messages:
    2,230
    Location:
    IL
    I suspect that your breaker is not just a ground fault breaker, but it is also an arc fault breaker. Then the dimmer switch generates noise which is interpreted as arcing by the AFCI.

    It could be that this would only occur as an interaction between your dimmer and the bulbs. You could try replacing your CFLs with non-CFL bulbs with the present dimmer. But you could just need a better dimmer.
  3. Jean-Claude JC Lussier

    Jean-Claude JC Lussier New Member

    Messages:
    7
    Location:
    Manitoba
    Fixed the problem. I had the breaker pigtail and circuit neutral connected to the neutral bar instead of the circuit neutral going back to the breaker. Thanks for the help.
    jbfan74 likes this.
  4. Reach4

    Reach4 Active Member

    Messages:
    2,230
    Location:
    IL
    I am glad you got it fixed. It makes me wonder why the breaker did not trip during the test you described this way: "If I bypass the switch and wire the lights direct the breaker, the lights turn on and the breaker doesn't trip." I now expect that you did not do your bypassing at the switch's box as I had envisioned.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,995
    Location:
    New England
    Depending on the length of the wiring and the draw you have on it, you can get different voltage drops across them (slight differences in resistance). There may have been enough of a difference to account for the 5ma current threshold to trip the GFCI.
  6. Jean-Claude JC Lussier

    Jean-Claude JC Lussier New Member

    Messages:
    7
    Location:
    Manitoba
    I have the same question. To bypass the switch I just removed the 2 black wires from the switch and put them together, flipped the breaker and the lights went on and stayed on for a least 5mins before I turned the breaker off. Weird eh?
  7. Reach4

    Reach4 Active Member

    Messages:
    2,230
    Location:
    IL
    Huh?
    With the circuit neutral wire not going through the breaker, the neutral leg of the GFCI would have 0 ma.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,995
    Location:
    New England
    And, the difference between the hot and the neutral would be more than 5ma...tripping the thing. The GFCI would think all of the current was going to a ground fault. Why it didn't trip in the other test doesn't make sense, if that description is totally accurate.
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