Pool tripping GFCI breaker

Discussion in 'Electrical Forum discussion & Blog' started by killavolt, Aug 4, 2009.

  1. killavolt

    killavolt In the Trades

    Messages:
    33
    Location:
    Southington CT
    A friend of mine has an inground pool. The last few days the pump has been tripping the GFCI breaker. He reset the breaker and the pump would run for a while and now the breaker won't reset. He replaced the pump, I replaced the GFCI breaker, making sure the neutral load was installed on the correct terminal of the GFCI and that the line and neutral were correctly wired in the panel. I replaced the twist lock receptical, with a 20A 125V (same as before) and the 20A switch. I also replaced the bubble rain tight cover as the gasket didn't look as if it was intsalled "rain tight". The GFCI doesn't trip when the pump is not plugged in. The pool and pump are correctly grounded as per NEC code 2008. The pool pump is on a timer if this helps.
    Any thoughts as to what could be causing the GFCI to trip? I took the twist lock pigtail off and installed a regular plug on and the pump runs fine (on another non GFCI circuit) . I taped the twist lock receptical and the switch contacts inside the weather tight box as well to make sure they were isolated from adjacent wires. The pump draws about 18A on a 120V circuit, which is pushing the ampacity of the circuit but it has run this way for about 6 years.
    Last edited: Aug 4, 2009
  2. Thatguy

    Thatguy Homeowner

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    Disconnect the neutral wire from the load side of the GFCI and check for no continuity between it and the ground wire.
    Reconnect the neutral.

    Measure the cold resistance of a 7-1/2w incand. lamp. It should be 100 Ω to 400 Ω. Call the value R.
    Put the lamp in series with the ground wire that serves the cable downstream of your GFCI.
    If the voltage across the bulb reads from 0.004R [0.4v to 1.6v] up to 120vac you've found your leakage path to ground. A normal reading would be 0.0005R for each 100' of Romex downstream of the GFCI.
    Last edited: Aug 4, 2009
  3. killavolt

    killavolt In the Trades

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    Location:
    Southington CT
    This is a GFCI breaker, on a dedicated circuit that serves only the pool pump. The neutral and ground buss bars in the panel are not seperated as this is a main panel. I have continuity between the neutral and ground at the pool's twist lock receptacle. I appreciate you taking the time to answer though.
  4. Thatguy

    Thatguy Homeowner

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  5. ActionDave

    ActionDave Electrician

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    Location:
    Colorado
    Try plugging the motor into another gfci protected circut.
    Test the pool circut with a load other than the pool motor.

    You should have continuity from neutral to equipment ground, they are joined at the service.
    If you take the load neutral off the gfci breaker then check for continuity it should read clear.
    However if you follow the first two suggestions you may not need to do this.
  6. killavolt

    killavolt In the Trades

    Messages:
    33
    Location:
    Southington CT
    Thanks fellas, I'm going over today to have another look. I'll report back with results.
  7. Chris75

    Chris75 Electrician

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    608
    Location:
    Litchfield, CT
    The motor is probably shot. just a stupid guess though. :rolleyes:
  8. Thatguy

    Thatguy Homeowner

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    Can you post a link to the one you are using?
  9. killavolt

    killavolt In the Trades

    Messages:
    33
    Location:
    Southington CT
    Replaced the pump motor yesterday brand new Hayward 1 1/2 H.P. I found where someone tied a lighting circuit into the pool's GFCI breaker circuit twist lock 4' sq. I'm gonna disconnect it and try a new pigtail on the pump motor. Water inside the pigtail could cause a ground fault.
  10. Chris75

    Chris75 Electrician

    Messages:
    608
    Location:
    Litchfield, CT
    1.5 hp motor at 120volts? highly doubt it.
  11. PEW

    PEW DIY Senior Member

    Messages:
    487
    Don't doubt, it they do exist. I have a gould irrigation 2hp running on 120.
  12. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

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    885
    Location:
    South of Boston, MA
    My pool pump is 1.5 hp & is switchable from 120 tp 240v
    At 120 it was rated for 18.6a Max - also a Hayward
    So I wired it for 240v
  13. Thatguy

    Thatguy Homeowner

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    So for GFCI breaker problems the first thing to check for is bootleg wiring.
  14. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    Actually all of the lights near my pool & in the pool cabana are GFCI protected

    But my pump is on its own circuit - now 240v
    Mine is rated at 18.6a @ 120x, so that only left ~168w for anything else
    So with a 150-300w flood light running that could kick out the 20a breaker
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    22,009
    Location:
    New England
    No CB should be loaded that high with a continuous load. You risk it potentially tripping regardless if there's a problem or not. Is that amperage the peak start current, or static while running?
  16. Thatguy

    Thatguy Homeowner

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    I don't have a GFCI breaker so I can't confirm these measurements, but if the pigtail goes to the neutral bar which is tied to the ground bus in the panel then this pigtail would see the >5 mA leakage current which trips the unit, in addition to the normal few mA of current required to power the GFCI integrated circuit electronics in the CB.
    The other white wire and the black wire going to the screw terminals which go to the load must be what goes to the differential current sensing toroid inside the unit. See Fig. 2 in the link below.
    http://www.national.com/ds/LM/LM1851.pdf

    I don't think you can use the lamp method with this, because the current in the pigtail is not just the leakage current and the lamp resistance would make the electronics do weird things.

    If you cannibalize the toroid out of an old GFCI receptacle, with a voltmeter and 'burden resistor' you can make your own differential 'former, with some ΔI of 5 mA or so giving some few hundred millivolts out. The sensing toroid in the figure uses a 1000:1 turns ratio, and the burden resistor on page 3 between pins 2 & 3 (R1) seems to be 100kΩ.
    I have the receptacle but not the time!
    Last edited: Aug 6, 2009
  17. killavolt

    killavolt In the Trades

    Messages:
    33
    Location:
    Southington CT
    I just found out that the previous electricains did work on this circuit left the system open for three weeks and water leaked into the conduit. It's old wire, not THHN or THWN. I told the home owner to contact them and they can pull new wire. The pump is a 1 1/2 HP running amperage is 18.6 and is really pushing a 20amp circuit. That's what's been there for 8 years though. I told the homeowner to have the other electricians pull a 240 volt circuit for the pool pump and convert it to 240V. Then it'll only draw about 8.3 amps.
  18. Thatguy

    Thatguy Homeowner

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    So with a megger the wire by itself should read less than 30kΩ.
  19. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    Sounds like the same pump I have
    That's why I upgraded to 240v, too much at 120v
  20. killavolt

    killavolt In the Trades

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    Location:
    Southington CT
    Exactly. i want to do right thing by the homeoner.
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