Bad breaker or ground fault?

Discussion in 'Electrical Forum discussion & Blog' started by cacher_chick, Mar 20, 2013.

  1. bluebinky

    bluebinky Member

    Messages:
    388
    Location:
    Santa Clara, CA
    Unhook the neutral and hot (load side) from the GFCI breaker and measure the resistance (VOM and/or megger) between the neutral wire and the neutral bar -- it should be open.

    In my limited experience with residential wiring (I am not a pro in that area), it's not uncommon for neutrals from different circuits to be intentionally tied together (obvious DIY hacks), but in that case, a GFCI breaker *should* always trip with a load on either circuit, and in theory possibly even without any load at all -- depending on the design of breaker.

    I still think what you describe sounds like a flaky breaker. Probably a manufacturing defect...
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,244
    Location:
    Land of Cheese
    As I mentioned before, this was an issue that I resolved some time ago. The reason for my post was to gain insight on how others would go about diagnosing such a problem.

    It was a neutral to ground short, and while my ohmeter showed infinity, the megger did not.

    I started at the panel and spit the circuit in half twice before being confident that it was in the lights. Unfortunately, I had to cut apart all 4 recessed cans to pinpoint the fault. The lights were split wired with 12-3 from 2 switches, and the short was located where the last recessed can junction box NM cable clamp was tightened on the cable.

    After replacing the lights, I loaded the circuit over 20 amps and the GFCI breaker never as much as whimpered.
    Last edited: Mar 22, 2013
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,532
    Location:
    North Carolina
    You answered your own question. This type problem is never easy to find
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