gfi problem

Discussion in 'Electrical Forum discussion & Blog' started by organic_riley, Nov 26, 2009.

  1. organic_riley

    organic_riley New Member

    I have a gfi at the panel serving a whirpool bath. I just changed tubs and have a problem. At the panel across the black and white leads of the gfi I have 120 volts. At the whirpool I have as follows --black and white 78 volts =or - , black and ground 120 volts, white to ground almost nothing. What gives any ideas. or
  2. krow

    krow Plumber

    Ontario, Canada
    Check the following
    black to white 78v = strange
    white to ground while operating = ?
  3. Thatguy

    Thatguy Homeowner

    Likely it's a phantom voltage. Put an incand. bulb across the voltage and measure again.
  4. jar546

    jar546 In the Trades

    Are you measuring voltage while the motor is running?
  5. jetlag

    jetlag New Member

    not 78 volt

    You have lost your neutral connection some where , the 78 volt is not real it is volt meter error that occurs when you try to measure with broken ground. Thats why I use 120 v bulb tester.. To confirm run an extension cord out to tub from a good outlet. check from neutral on cord to hot on tub you should have 120 v. that confirms neutral is out on tub.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    White to ground should be nothing, not "next to nothing" if your meter is correct. depending on where you lost your neutral, and I suspect it is near the GFCI, the 78 volts could be feed through from the circuitry in the GFCI, in which case the neutral WIRE is intact from the GFCI to your tub. I have had it happen several times.
  7. frenchie

    frenchie Jack of all trades

    Google "induced voltage" aka "phantom voltage".

    It's not meter error in the sense that the meter's faulty. There really is 78v there. Only it's at zero or near-zero amps - so a bulb tester will show zilch.

    The hot wire creates a magnetic field, which sets up a (weak) voltage in the dead wire. He could disconnect both ends of the dead wire from anything, the tester would still show the 78v. But connect a load to it - like a lightbulb, or a bulb tester - it disappears & your meter will show zero volts.
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