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Thread: Trying to debug GFCI tripping

  1. #1
    DIY Junior Member rrauenza's Avatar
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    Default Trying to debug GFCI tripping

    Hi,

    I'm having a strange GFCI problem.

    I have a lamp post in our driveway that has underground wiring. It goes through a GFCI box before heading underground. It is UF cable, mostly in a PVC conduit. (comes down the wall in a flex pipe, goes under some gravel, then into the conduit, then to the lamp post base, and up)

    Some time ago I nicked the cable and so spliced it. First I used one of those shrink wrap kits from home depot -- worked for a while, then shorted - tripped the GFCI. I removed it and just wire nutted it with "waterproof" nuts and put a plastic irrigation box over it and left the wires uncovered by the gravel. It worked fine in this state - no trips.

    Not happy with that (and I shouldn't be... shame on me), I intended to eventually just run a new line -- but then I saw the Uraseal products. So I ordered one, stuffed the splice into one of their products, let it cure, and .. what? It trips again! It's not buried yet -- it is still in the open air.

    I took apart the GFCI box, found another in my box from a remodel (covered in paint..), and it also trips. Disconnected the load wires, and it doesn't trip. Measured the ohms from the hot to neutral/ground load wires: infinite ohms. (is the multimeter just too low of voltage to pick up the leak?)

    I'm about to just throw my hands up and try to pull a new cable.

    Anything else I should do to troubleshoot this?

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    Your answer lies in the next to last line in your post. "pull a new cable."

  3. #3
    DIY Junior Member rrauenza's Avatar
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    Quote Originally Posted by jwelectric View Post
    Your answer lies in the next to last line in your post. "pull a new cable."
    Yeah.... It's only about 30', I just don't know if I call pull out the existing 12 gauge UF without redigging the whole trench. I might try digging and cutting the conduit at the foot of the lamp post. Luckily I can replace it with 14, as the circuit is a 15 amp circuit -- the 12 was put in because that was what was on hand.

    As to root cause ... forgot to mention I also took out the light bulb (compact fluorescent screw-in). Read up on all kinds of weird GFCI issues like capacitance, tiny leakages, etc. last night. I wonder if the splice has just pushed me over the 5ma edge that I was already close to. Uraseal actually wants me to cut off the splice and send it to them for analysis! I'm really skeptical its the splice. I don't know how it could be -- it's not even buried.

    I also need to redo another test again that I didn't mention -- I recall that I removed the load from the first GFCI module (outlet-less) and I believe it tripped with no load wires. Which is why I tried the 2nd GFCI I had in my toolbox. That one only tripped with load wires connected (technically, no load since I had removed the bulb). That would indicate that the first GFCI may be going bad.

  4. #4
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by jwelectric View Post
    Your answer lies in the next to last line in your post. "pull a new cable."
    I can agree 100% without hesitation here with every word of advice JW gave you on this. Replace that cable after everything you have described. I would. (Not that JW needs any support here, lol).

    Sometimes you just have to do what you have to do to get it done correctly. I doubt if its the CFL bulb, but the socket the bulb screws into may be infested with bugs or thier remains causing enough leakage to ground. Replace the cable anyway.
    I am definitely not a pro plumber, but I am a pro crastinator

  5. #5
    Consultant cwhyu2's Avatar
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    Quote Originally Posted by BobL43 View Post
    I can agree 100% without hesitation here with every word of advice JW gave you on this. Replace that cable after everything you have described. I would. (Not that JW needs any support here, lol).

    Sometimes you just have to do what you have to do to get it done correctly. I doubt if its the CFL bulb, but the socket the bulb screws into may be infested with bugs or thier remains causing enough leakage to ground. Replace the cable anyway.
    And I agree with JW and Bob.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    I had a similar intermittent tripping of a GFCI, and this was in the house, not outside subject to weather. The GFCI daisy-chained to 4 more receptacles. I kept disconnecting things until I found the run that was bad...unfortunately, it happened to be the last one in that chain...I ended up running a new wire to it and all's well now for nearly a year. In my case, it may have been a staple, a nick, or who knows what, but replacing the cable fixed it (and this was with nothing plugged into any receptacles!). It would work for a few weeks or maybe a month, then randomly trip.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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