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#169880 - 10/18/07 07:36 PM GFCI Operation
AndyM Offline
New Member

Registered: 10/18/07
Posts: 6
Loc: Quincy MA USA
I am a power electrical engineer & have learned (the hard way) that I am better at electrical work on paper then hands-on. I have had an electrican do some work at my house including replacing an old (~30 yrs) duplex receptacle that feeds a clothes washer. This outlet had no issues other then being old. He replaced it with a GFCI for the reasons of its in the unfinished basement. Unfortuntely the GFCI is operating when the washer is running. During 1 washing cycle it tripped twice.

As I understand the operation of a GFCI it monitors the line & neutral lines & operates if there is over a few millaamps difference between them. So I see that maybe the washer has some intermittent internal fault or short but do GFCIs have a know issue with false operations under certain 'non-fault' conditions?

I have the electrican coming back & I have stopped using the receptacle, but am more interested in getting more info for when the electrican comes back.

Thanks in advance for any info.


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#169884 - 10/18/07 07:55 PM Re: GFCI Operation [Re: AndyM]
wire_twister Offline

Registered: 07/25/07
Posts: 265
Loc: Georgia USA
In my experience GFCIs sometimes will not run motor loads, nothing wrong with the load, or the gfci just some nuissance tripping. Solution: install a 20a single receptacle for the washing machine, per 210.8 ex 2

Life is tough, Life is tougher when you are stupid

#169890 - 10/18/07 09:17 PM Re: GFCI Operation [Re: wire_twister]
SP4RX Offline

Registered: 10/01/07
Posts: 56
Loc: Edmonton, Alberta,
The most likely scenario that I can think of would be that your washing machine's motor makes use of a capacitor. If that is the case then while the capacitor is charging (storing electrons) the neutral would be seen as having a different level of current, which the GFCI would interpret as a ground fault.
But then again I could be completely out to lunch! \:D

#169892 - 10/18/07 09:58 PM Re: GFCI Operation [Re: SP4RX]
gfretwell Offline


Registered: 07/20/04
Posts: 9026
Loc: Estero,Fl,usa
I say the washing machine has an internal short. All this "capacitor charging" and other excuses just do not pass the "Kirchoff" test.

If you are really brave/careful you could prove it by plugging in a 3 prong adapter and monitor the voltage between the ground and the pigtail on the adapter. I bet you see some. If you think this is just a phantom voltage make the connection to ground through a 50k resistor (not enough to trip the GFCI) and measure the voltage across the resistor. Just be sure you are not touching the washer when you are doing it.
Greg Fretwell

#169915 - 10/19/07 06:48 PM Re: GFCI Operation [Re: gfretwell]

Registered: 03/29/04
Posts: 252
Loc: Kingwood, TX USA
Leakage may be thru the water lines not on the 3 prong.

#169917 - 10/19/07 08:01 PM Re: GFCI Operation [Re: WESTUPLACE]
JoeTestingEngr Offline

Registered: 11/04/05
Posts: 786
Loc: Chicago, Il.
I've seen cases where folks have tried to put a GFCI in place of a duplex in a shared neutral circuit. Was your GFCI at the end of the line or were wires connected to the load side screws? The outlet will trip at the flip of a switch.

#169918 - 10/19/07 08:43 PM Re: GFCI Operation [Re: JoeTestingEngr]
twh Offline

Registered: 03/11/04
Posts: 895
Loc: Regina, Sask.
Perhaps a ground fault in a solenoid, or perhaps a bad GFI, or is it, in fact, a GFCI?

#170041 - 10/24/07 08:28 PM Re: GFCI Operation [Re: AndyM]
AndyM Offline
New Member

Registered: 10/18/07
Posts: 6
Loc: Quincy MA USA
Here is an update. Looks like a bad GFCI. The electrican installed a new GFCI and it seems to be working fine. I have only run 2 full loads thru the washer, but the previous GFCI didn't last half a run.

Thanks for all the feedback.


#170056 - 10/25/07 06:46 AM Re: GFCI Operation [Re: AndyM]
Mike Wescoatt Offline

Registered: 06/17/01
Posts: 164
Loc: Cedar City, Utah
Was it a different brand or the same brand? I've seen different brands with different tolerances that still meet the UL listing.
Mike Wescoatt


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