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Thread: GFCI Distance Too Far?

  1. #11
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    Quote Originally Posted by ramsy View Post
    You got me there. Can we check capacitance at the receptacle with a volt meter, or HVAC meter capacitance function?
    Possibly, but you need to know how to convert that into reactance to know how much current will flow. Something I almost never have to do so I can't help off the top of my head.

  2. #12
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    Quote Originally Posted by SceneryDriver View Post
    The conduit could be filled with water after a year; pretty common via condensation. That water will increase the capacitance between the circuit conductors. If the capacitance gets high enough - and at 100' of run it might - the GFCI breaker can read that as a ground fault and trip.

    If you can (burial depth, etc...), replacing the GFCI breaker with a GFCI receptacle would eliminate that as an issue.


    SceneryDriver
    Why would capacitance take 10 minutes to show up?:

    "he calls back and says he installed a new pump w/new cord and tried to run it. He says it ran for about 10 mins. then tripped."

    Dont most underground conduits eventually get full of water?
    Electricians do it until it Hertz!

  3. #13
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    Quote Originally Posted by JFletcher View Post
    Why would capacitance take 10 minutes to show up?:

    "he calls back and says he installed a new pump w/new cord and tried to run it. He says it ran for about 10 mins. then tripped."

    Dont most underground conduits eventually get full of water?
    When you only need 4-6 mA to trip, having something like 3.5 mA leaking constantly leaves you smaller window for other things to make it trip that may not otherwise make it trip.

  4. #14
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    Are you guys serious about this capacitance comment or you are joking??
    Edward
    The only thing I know, is the progressive discovery of my ignorance


  5. #15
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    Quote Originally Posted by edward View Post
    Are you guys serious about this capacitance comment or you are joking??
    Not a joke. A capacitor is two metal plates with insulating material between them, you have capacitance between conductors in a cable or raceway, but is such a poor capacitor it normally isn't something we take much consideration of. Make those conductors a hundred, two hundred feet long, it starts to become enough capacitance to matter when you consider the low current trip level of a GFCI. Now fill the raceway with water, and depending on the purity of the water can make an even better capacitor out of it.

  6. #16
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    The issue of some pool/spa pumps causing GFCIs to trip is only for the type of pumps that are variable speed; they have a VFD attached to the pump itself and are 3-4x more expensive. Generally that's not something you would retrofit into an existing unit without an extensive reworking of the entire control system.

    Cable capacitance would have been a problem from day one, unless as mentioned, there has now been a water intrusion. Dog pulling on the cord may have damaged the cord at the pump and at a connector coming from the disconnect. If he only replaced the pump itself, he may have only fixed half of the problem.

    Ah wait, I just noticed that the cord was replaced; never mind...

    New theory; there is too much voltage drop on that distance with the wire size you used and the pump is over loading. It was OK for a while, but now something has changed with the local utility feed and where you were on the ragged edge at first, you are over that edge now.
    Last edited by Jraef; 07-17-17 at 08:13 PM.
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  7. #17
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    Quote Originally Posted by edward View Post
    Are you guys serious about this capacitance comment or you are joking??
    It is a good thought.

    A neighboring village had an overhead ACSR 2 wire well control that would stick on after a rain. (connections all good and no faults). Your GFCI would require far less current.

    (I would still meg it)
    Tom
    TBLO

  8. #18
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    Quote Originally Posted by ptonsparky View Post

    (I would still meg it)

    Are (and others) saying to Meg just the wires/conductors or the pump as well?
    If the pump too, remember it is a new pump.
    If you aim at nothing, you will hit it every time!

  9. #19
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    Quote Originally Posted by Little Bill View Post
    Are (and others) saying to Meg just the wires/conductors or the pump as well?
    If the pump too, remember it is a new pump.
    If your looking for a ground fault, Meg the conductors.

    Motor Running for ten minutes makes me think you should be looking for something else, but if you're there already, check everything.
    Tom
    TBLO

  10. #20
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    Quote Originally Posted by ramsy View Post
    Bring a Megger tester, since a ground faulted feeder may eventually electrocute everybody.

    Besides, if underground conduit is 12" deep, rather than 18", the GFCI breaker is required to protect the feeder at 12" burial depth.

    Bring a Surge-Suppressor outlet, with EMI filter, to replace the pump receptacle, not a GFCI outlet.
    A surge suppressor after a GFCI breaker will guarantee nuisance tripping of the breaker.

    -Hal

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