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Thread: GFI tripping

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  1. #1
    DIY Junior Member ferd's Avatar
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    Question GFI tripping

    Installed a gfi duplex in place of standard duplex. Vent fan uses the same feed. gfi trips when you tune the fan off. Wired the fan direct to the feed, not thru the gfi, but gfi still trips. Any suggestions welcome. Thanks

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    It is wired incorrectly or something in the box is touching something

  3. #3
    DIY Junior Member ferd's Avatar
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    Already checked. gfi isn't even in the box to touch anything.

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    Plumber jimbo's Avatar
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    Look for an issue with your neutrals. If a neutral connection at the load has a path to return thru the GFI, but also another neutral wire connected, then the current can split and the gfi sees a fault. Or if the current from a different load is returned to the gfi neutral...same thing,

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    DIYer, not in the trades LLigetfa's Avatar
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    Some of the sparkies on this forum scoff at me when I say that induction loads can induce a voltage when turned off but that is exactly what is happening. The magnetic field in the motor collapses just like an ignition coil does when the points open. Some motors can act as generators as the rotation inertia diminishes when the power is removed. This can trip a GFCI.

    The fact that it is tripping a GFCI when the fan is not protected by the GFCI however sounds very suspiciously like a poor neutral bond or a very long run of light gauge wire.

    The common cure for motor loads tripping a GFCI is to use a double pole switch designed to switch 240 volt loads.

    http://homerepair.about.com/od/elect...ch_types_3.htm

  6. #6
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by LLigetfa View Post
    Some of the sparkies on this forum scoff at me when I say that induction loads can induce a voltage when turned off but that is exactly what is happening. The magnetic field in the motor collapses just like an ignition coil does when the points open. Some motors can act as generators as the rotation inertia diminishes when the power is removed.
    This is very true and I agree with your comments

    Quote Originally Posted by LLigetfa View Post
    This can trip a GFCI.
    This is very untrue and I completely disagree.
    What makes a GFCI open is an imbalance between the hot and neutral and this alone.

    Quote Originally Posted by LLigetfa View Post
    The fact that it is tripping a GFCI when the fan is not protected by the GFCI however sounds very suspiciously like a poor neutral bond or a very long run of light gauge wire.
    This again would have no effect on a GFCI. A loose neutral would only open the circuit

    Quote Originally Posted by LLigetfa View Post
    The common cure for motor loads tripping a GFCI is to use a double pole switch designed to switch 240 volt loads.
    a waste of time and money

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