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Discussion in 'Electronic Basics' started by Sonny, Oct 28, 2004.

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  1. Sonny

    Sonny Guest

    Our house is 7 years old and there's a GFCI outlet (always on)
    installed in our garage. I wanted to tap into the GFCI outlet to have
    electricity for the new fluorescent lights I installed in the garage.
    I didn't want to tear up the drywall so all I did was take an old
    heavy duty extension cord and cut-off the female side, stripped the
    wires and connect to the new outlet and plugged the male side of the
    extension cord to the GFCI outlet. After doing so, I tested to see if
    the new outlet would provide power and it did, also checking with a
    tester and everything was ok. I then proceeded to connect the new
    outlet to the switch (middle of the run) that controls the fluorescent
    lights using 14/2 NM gauge wiring. Every step of the way, I made sure
    the wiring was done properly by using the tester. Now after all this
    was done, I plugged the extension cord to the GFCI outlet and turned
    on the lights using the switch. And long behold, I have light in the
    However, once in a while (and it seems to be random), when I turn-off
    the lights using the switch, the GFCI would trip. Then I would have
    to reset and all is well again. I read in previous posting (back in
    2000), someone had a similar problem, but his GFCI was tripping when
    the lights were turned on. And it would seem that if I did the wiring
    incorrectly, the GFCI would also trip when I turn on the lights NOT
    when I turn them off. And again, it would be random. Also, to check
    if the extension cord was the culprit, I changed the wiring using 14/2
    NM gauge, and the problem still exists. What did I do wrong? Is the
    GFCI that sensitive to detect a very small variance?

  2. Mike

    Mike Guest

    Did you use a new switch? Sounds like some voltage is draining to ground...

  3. Sonny

    Sonny Guest


    Thanks for the reply. Yes I did, but if some voltage is draining to
    ground, wouldn't that indicate that the switch is not properly
    grounded? But when I tested the wiring with a tester, all seems to be
    ok. I've read from other postings that it's not really recommended
    connecting fluorescent lights in the same GFCI wiring because of the
    ballast or something like that.
  4. Mike

    Mike Guest

    Here's an interesting post with a guy that never experienced a GFCI trip
    with all sorts of appliances, including fluorescent fixtures:

    To answer your question: if voltage is draining to ground, you have a short
    somewhere. Doesn't necessarily mean that your switch is not grounded. If you
    had a bad switch that was leaking current to its metal frame, which wasn't
    grounded, you'd most likely get zapped. Here's how a GFCI looks internally
    (you can infer operation from this):

    I'm not too familiar with ballast internals. Sorry. Perhaps your GFCI is too


    I have had my share of GFCI problems
  5. Rich Grise

    Rich Grise Guest

    That would have been my first guess. It's tripping on the glitch.

    Try a little snubber across the switch, say 1K 1W in series with
    about 1-10 nF, 600V.

    Good Luck!
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