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Thread: Failed GFI Outlet?

  1. #1
    Join Date
    Jan 2003
    Location
    Mebane, NC, USA.
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    10,624

    Failed GFI Outlet?

    I noticed some outlets in my shop stopped working this weekend. Outlet closest to the breaker is a GFI. It would not reset. I disconnected everything downstream and verified good power at the outlet. Still would not reset. Just want to verify they can fail in this manner or might there be an issue on the circuit? Power comes straight from the breaker to this outlet and was existing in the basement - I only replaced the outlet with a GFI.
    David

    The chief cause of failure in this life is giving up what you want most for what you want at the moment.

  2. #2
    Join Date
    Aug 2004
    Location
    King of Prussia, PA, USA.
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    I have one that failed exactly the same way - just one day stopped working. I swapped it for another one and everything was fine.

    Not sure why, but yes - it is possible.
    -Joe

  3. #3
    Almost certain you have a bad GFI (or a GOOD one just doing its job). Easy enough to put in another one and check it. As for the other outlets, most GFI outlets take out any downstream outlets when they fault. Probably yours, too.
    ...eight, nine, TEN! Yep! Still got all my fingers!

  4. #4
    MilDoc Guest
    They contain sensitive elctronic components that can be damaged by power surges and other causes. In many cases, damage to the internal transient voltage surge suppressors that protect the GFCI sensing circuit is responsible for failure of the device. Wet or damp places also can lead to failure. But they've gotten better over the years.

    One thing an electrician friend of mine told me years ago. If a GFCI trips, don't just reset it. Reset, then test to make sure it trips again, then reset.

  5. #5
    Join Date
    Jul 2005
    Location
    Ballston Lake, NY, USA.
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    16

    Replace the GFCI first

    Yes, they can fail exactly in that manner. Or it could be a fault in the wiring or outlets wired downstream from the device. It's probably easier to replace the GFCI first, before trying to troubleshoot downstream leakage.

    If the second one trips the same way, you've got a leakage to ground somewhere downstream from the outlet. Then it's time to see if a mouse (or pet) chewed on a cable, or if there's water infiltration in that Sump pump you've forgotten is also wired downstream on the same circuit, or something else is leaking current.

    At it's heart, the GFCI compares hot-side current to neutral-side current (thru a differential current transformer if it matters) and triggers if the imbalance between the two hits a certain point, typically 5 milliamps for home use.

    (Contrast this to a circuit breaker, which is an over-current device which monitors the total current flowing thru the hot side, and triggers at the rated load, for example 15 amps.)

    If it trips after replacement, it's not a fluke: There's more current going out on the hot side than is returning on the neutral. This is going somewhere to ground, hence the term 'ground-fault.' Consult a qualified individual, who will cut power, check it dead, and then begin looking for mechanical breaks, water infiltration, or some other sign of damage or deterioration.

    Good luck. Oh, and test your GFCI's regularly. Like a fire-extinguisher or seat-belt, if you need it, it had BETTER work. You change the oil in your car and the batteries in your smoke detectors, right ?
    Last edited by JimZ; 08-14-2006 at 10:21 PM.

  6. #6
    Join Date
    Dec 2002
    Location
    Katy, TX, USA.
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    16,954
    Quote Originally Posted by JimZ
    ...
    Good luck. Oh, and test your GFCI's regularly. Like a fire-extinguisher or seat-belt, if you need it, it had BETTER work. You change the oil in your car and the batteries in your smoke detectors, right ?
    My car has oil?

    And yes GFCI's can easily fail.
    Loring in Katy, TX USA
    If your only tool is a hammer, you tend to treat all problems as if they were nails.
    PM me (with your e-mail address) for a copy of the BT3 FAQ current vers 4.13

  7. #7
    Join Date
    Sep 2004
    Location
    Milwaukee, WI
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    Quote Originally Posted by LCHIEN
    My car has oil?

    And yes GFCI's can easily fail.
    Can they fail to trip? Are there any documented instances of a GFCI not tripping as expected and an injury resulting?

  8. #8
    MilDoc Guest
    Quote Originally Posted by cgallery
    Can they fail to trip? Are there any documented instances of a GFCI not tripping as expected and an injury resulting?
    .

    Yes, if damaged. The newer models are less prone to this than they were 20 years ago, but there have been a lot of reports of GFCI's damaged (often by voltage surges; CPSC web site has articles on this), and that would still allow power to go through after being reset. That's why my electrician friend said, if tripped, find the reason and fix it, then reset, then press the test button to make certain it will still work.

    And yep, I test mine every month, just like checking the oil.

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