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shore power gfci tripping solution found [message #356460]

Mon, 06 July 2020 13:23

rgogan

Messages: 82
Registered: February 2004
Location: Milwaukee, WI

Karma: 0

Member

Suddenly, unless I plugged into a non GFCI shore power outlet, the GFCI would trip. My 44 year old plug looked suspicious as the individual wires have been creeping out of it gradually for years. However, before I amputated the cord end and put on an aftermarket new four pronged 50 amp plug, I did some trouble shooting. There was indeed some high resistance between the hot wire and the ground which disappeared when I turned off the vacuum cleaner breaker. Now I can plug into the GFCI without it tripping. Have not started trouble shooting the vacuum cleaner outlet or the vacuum cleaner itself. With my luck, some mice probably took up residence in the vacuum cleaner electrical and chewed through the wires. Anyone else experience this problem?

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Re: shore power gfci tripping solution found [message #356467 is a reply to message #356460]

Mon, 06 July 2020 17:42

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Many times it is the hot water heater that causes the GFI to trip. The fault is in the heating element, usually after the heater has gotten low on water and the element was exposed. The element overheats quickly and burns out. This sometimes leaves a current path from the internal element heater to the external metal housing.

Turning OFF the hot water heater does not fix the issue, because the current path is from Neutral to ground. The some return current can now flow though the ground which upsets the balanced current flow in the hot and neutral... thus trips the GFI.

Tracing the abnormal resistance from ground to neutral and you end up at the water heater! even though you may have the water heater turned OFF...

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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Re: shore power gfci tripping solution found [message #356471 is a reply to message #356460]

Mon, 06 July 2020 19:54

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

Bruce good explanation. Same N-G leakage could occur in vacuum motor if there is mouse pee etc between the neutral side motor brush and case ground. Easy to test, just unplug vacuum under the frig.

John Lebetski
Woodstock, IL
77 Eleganza II

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Re: shore power gfci tripping solution found [message #357310 is a reply to message #356460]

Tue, 28 July 2020 15:19

rgogan

Messages: 82
Registered: February 2004
Location: Milwaukee, WI

Karma: 0

Member

At another GFCI shore power outlet, my GMC with the vac breaker turned off still tripped the GFCI. It tripped it in fact with all the breakers turned off. It tripped it with the hot wires disconnected from the buss. It tripped when the ground was disconnected from the breaker box. I finally decided that it was the original molded four prong plug that had shorted the ground to the neutral that was tripping the GFCI. I tried to tear it apart to see where it had shorted, but found it was too much of a job. Placed a new four prong plug on the end of the old cable and I have no further problems with the GFCI's tripping.

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