GFCI weirdness

JHZR2

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A number of years back, I installed a sub panel in my basement. It runs some 240V AC loads and provides a few circuits. Those circuits are in my basement, one dedicated for the sump pump, one dedicated for the dehumidifier.

The dehumidifier, as a non critical load, is on a gfci since I figure it's on the ground and in case of a flood, I'd like it to trip there asa first line of defense. The gfci and dehumidifier work perfect.

I have another circuit fed from my main panel, which is for other basement outlets. The first outlet in the line is a gfci. Recently the GFCI has been tripping, and my wife has correlated it to when the dehumidifier comes on.

There is no chance of a shared neutral, it doesn't happen any other time, so I assume the one gfci is bad. Any ideas why this would happen? Not only is it two different circuits, but one is actually off a subpanel. I'm tempted to swap the tripping GFCI to a regular outlet, but I'd rather not.

I did have a fluorescent light on a different circuit, which would trip a GFCI outlet on the SAME circuit. I plugged the light in via a surge protector and it has not happened since. I guess it needed the filter. Perhaps it's something like that for the dehumidifier? Even if so, it's different circuits this time, so any startup noise issues would need to resonate all the way to the main panel somehow...

Thanks!
 
Check your neutral and ground at the sub panel. Make sure theyre not bonded there
 
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Originally Posted By: mx5miata
Check your neutral and ground at the sub panel. Make sure theyre not bonded there


They're definitely not.
 
Normally appliance loads arent on gfci due to the start up load of a motor or compressor could trip the gfci.
 
Did you go down the buss bar to check if any lugs come loose over time a loose neutral can cause resistance. And be tripping on ground
 
Originally Posted By: mx5miata
Normally appliance loads arent on gfci due to the start up load of a motor or compressor could trip the gfci.


Agreed, but since the dehumidifier is in my basement, next to the sump hole (which never has water, fwiw), on the ground, I figure if there ever was water I'd like a GFCI to protect it.

It's not like a freezer or something that could have bad consequences if the GFCI tripped. And it NEVER has.

The GFCI that IS tripping is a basic loop of outlets in my basement, which only feed a few lights and a battery charger. No appliances. Yet it is tripping, even with all loads off!

Originally Posted By: mx5miata
Did you go down the buss bar to check if any lugs come loose over time a loose neutral can cause resistance. And be tripping on ground


No I have not. Good point. But the GFCI that is tripping does so even if all loads on it are off.
 
Good chance the gfci is on its way out. Have you had any power surges or lightning lately the logic board inside may have took a hit electricity is a funny thing
 
I had a similar problem in my garage. The GFCI outlet kept tripping. Since it was 18 years old I replaced it and haven't had a problem since. I did install a Leviton brand. Is that bad?
 
I had a similar problem in my garage. The GFCI outlet kept tripping. Since it was 18 years old I replaced it and haven't had a problem since. I did install a Leviton brand. Is that bad?
 
GFCI’s can go bad with time. Replace it if you can’t find anything else.
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Originally Posted By: Urshurak776
I had a similar problem in my garage. The GFCI outlet kept tripping. Since it was 18 years old I replaced it and haven't had a problem since. I did install a Leviton brand. Is that bad?


Not necessarily, but they had some bad batches of 15A ones model GFTR 1 sold through Home Depot during past year or so. They would trip all by themselves 2-3 days after installation, with red LED flashing indicating that it won’t allow you to reset it.
 
I had a similar issue with my front and rear outside outlets they randomly pop about 5x a year and have 2 gfci outlets in series.. the 100w worth of Christmas lights does it the most often..



Another electrical issue I had was the powerline networking adapter was popping my cafci breaker. when the 500w window a/c turned on.. (after 5-30min or so)
 
To the OP: if it keeps tripping without any load I suggest replacing it. I would suggest Pass & Seymour / Legrand if aestethetics are important (i.e. you want it to look clean and nice and stay flush with the cover).
 
Originally Posted By: JHZR2
The GFCI that IS tripping is a basic loop of outlets in my basement, which only feed a few lights and a battery charger. No appliances. Yet it is tripping, even with all loads off!

We saw similar symptoms. Your wife noted when tripping occurs - only a symptom (correlation). An indication of where to start looking for hard *facts*.

A new paper shredder (on same circuit but not powered by that GFCI) would trip a GFCI. I put an oscilloscope on that item with similar symptoms. Spikes from that new shredder would intermittently cause the GFCI trip (typically less than 1% of the time). So the investigation continued.

A new shredder's electronics had holes, painted label, and PC traces for a line filter. Engineers knew that line filter was necessary. Apparently business school graduates then did what cost controller routinely do. Shredder worked without that line filter. So they saved 50 cents - removed filter parts and install a wire jumper.

This shredder created spikes on every startup. But, as usual, over 99% of those startups did nothing harmful. Only about one startup per day caused that GFCI (on another receptacle box across the room but on the same circuit breaker) to trip.

Shredder was completely defective - since it only caused a GFCI trip less than 1% of the time. That conclusion difficult for many - but exactly how reality works. Defect exists constantly. Resulting failure is rare.

Line filter was taken from an old TV. Of course, all holes and PC traces existing on that new shredder's PC board existed; filter parts fit in perfectly. Many years later and a GFCI never tripped again. Why? Oscilloscope showed no spikes after that required (and cost controller removed) filter was restored.

Shredder was used so often over those many years that an internal gear finally failed. Offending shredder that caused maybe one GFCI trip per day (before a line filter) never caused a GFCI trip years later (after the filter was installed).

Symptoms (what the wife observed) can point to a suspect. Hard facts (oscilloscope, missing line filter) were necessary to make a conclusion. However if a business school graduate fixed the dehumidifier's design, then its also required line filter might be missing. Empty holes for the required filter may be obvious.

GFCIs never fail intermittently. Either it does not trip (or reset) at all. Or it is good.

A problem (as most are) was created by people who are trained decision makers but have no idea how the work gets done. (Same type people also killed seven astronauts on the Challenger using same decision maker's training.)
 
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