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Thread: GFI won't trip

  1. #1
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    GFI won't trip

    I have a GFI recept in a kitchen on a 2 wire system-no ground.The GFI will trip when you press the test button.It will not trip using a plug in GFI tester.My question is would it make any difference to install GFI brkr?I don't think it will. I'd appreciate any input.Thanks

  2. #2
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    won't make a difference. GF "testers" won't work on two wiire systems ..
    manufacturer recommends using their test button. If that works, you are good to go,.
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  3. #3
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    There is no ground so the tester is not making a connection to ground for the test.

  4. #4
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    Quote Originally Posted by dale46 View Post
    I have a GFI recept in a kitchen on a 2 wire system-no ground.The GFI will trip when you press the test button.It will not trip using a plug in GFI tester.My question is would it make any difference to install GFI brkr?I don't think it will. I'd appreciate any input.Thanks
    A GFCI receptacle's test button works by connecting a resistor from the hot wire after the current sensor to the neutral ahead of the current sensor, which mimics someone receiving a shock.

    A plug-in GFCI tester works by connecting a resistor from the hot wire after the current sensor to the ground wire, because it has no way of accessing the neutral ahead of the current sensor.

    No ground connection results in no shock-mimicking current. Note that a ground "cheater" (3-prong to 2-prong adapter) with the ground tab or wire grounded, will allow a plug-in tester to function.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  5. #5
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    Mar 2005
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    Thanks for the feedback.I thought the problem was probably with the 2-wire system,not having a ground wire.Thanks

  6. #6
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    Quote Originally Posted by dale46 View Post
    Thanks for the feedback.I thought the problem was probably with the 2-wire system,not having a ground wire.Thanks
    Yes that's it and that is one reason why you should only be using the test button to test the GFCI receptacle in the first place. Those plugin testers can actually give you a shock if the conditions are right. Larry has a nice explanation as to why one method (the device test button) works and the other doesn't.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  7. #7
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    All 3 prong receptacles that are GFI protected but only have two wire circuits should have stickers on them that read "GFI Protected / No Equipment Ground". I would guess that part of the reason for this is because when you put a plug tester in such a receptacle, it will not trip the tester... The only way to test those receptacles properly is to trip the Upstream GFI and verify power is dead.

    GFI receptacles and Breakers work perfectly well with two wire systems, the ground wire is irrelevant for their operation
    Electricians do it until it Hertz!

  8. #8
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    Quote Originally Posted by dale46 View Post
    I have a GFI recept in a kitchen on a 2 wire system-no ground.The GFI will trip when you press the test button.It will not trip using a plug in GFI tester.My question is would it make any difference to install GFI brkr?I don't think it will. I'd appreciate any input.Thanks
    that is the way it should be. the plug in testers are pretty much useless for testing the GFI part of a receptacle. use the test button on the receptacle.
    Bob

  9. #9
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    Quote Originally Posted by petersonra View Post
    that is the way it should be. the plug in testers are pretty much useless for testing the GFI part of a receptacle. use the test button on the receptacle.
    Thanks for the input. I didn't realize those GFI testers test between hot and ground.I thought they tested between hot and neutral mimicking how the device actually works.

  10. #10
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    Quote Originally Posted by dale46 View Post
    Thanks for the input. I didn't realize those GFI testers test between hot and ground.I thought they tested between hot and neutral mimicking how the device actually works.
    The neutral slot on the receptacle is after the internal circuit monitor so no plugin tester will connect before it leaving only the EGC for it to send the test current.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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