Ground Fault Electrical Help

[nocheepgas]

About 2 years ago I installed a 125 amp sub panel to my out building (per code and inspected) Right now it only has one circuit on it, feeding 4 receptacles. The first receptacle in the line was a GFI. The GFI recently went out, I thought I had a bad receptacle, so I replaced it. Turns out it won't reset either. The cable to the sub panel is all in conduit and the one circuit is also in conduit. I disconnected all downstream load circuits from the receptacle, but no luck there. How do I go about tracking down a ground fault, exactly what's the mechanics of the problem, what am I looking for?

[Frank Motoweld]

Ground faults

I believe those things work on a differantial of voltage between the 2 sides!So if one side has more than a prescribed differance from the other,the GFI will trip!!!
I'm not shure of a better way to word it,but it's something along those lines

Frank

[con_fuse9]

A "ground fault" is when not all the current going out the hot, comes back on the neutral (basically the current on the black wire doesn't equal the current on the white). Basically it means that some where, power is going to ground.

Think about someone dropping a radio in a bathtub. Metal pipes (like on the drain) make a nice path to ground. The outlet senses that some electricity is going elsewhere and pops, thus saving the swimmer in the tub.

I would disconnect the other outlets and add them back one at a time. Take a good look at the other plugs as well. Make sure there is nothing inside the plugs.

If the wiring is in conduit, you can alsways try pulling a new wire through (see if some critter bit through it - or perhaps that picture you hung on the wall pierced the plastic conduit?

Good Luck

[WyoRoy]

Just in case...black on brass?

[nocheepgas]

Black on Brass-OK
Other Outlets-Disconnected
No nails in the wall

Yes, I understand it's tripping due to a voltage differential, sensing a variance between black coming in and white (or ground) going out. I just don't understand where that leaves me to look?? If it's only the power from the sub panel breaker to the outlet, then replacing that wouldn't be too bad. If I have to look at the 160' of #1 copper from the main panel to the sub panel, that's an entirely different story. That was one hard pull with 4 bends!

[Broccoli1]

Do you have Power to the Sub panel?

GFI's need Power to reset.

[Burnt hands]

nocheepgas,

I had a similar situation with my panel.

Electrician wired in a GFI breaker at the main panel and installed individual GFI outlets on that circuit.
Belt and suspenders approach but it turned out they were fighting each other giving lots of nuisance trips.

Replaced the GFI breaker and problems stopped. Still have outlet protection.

Since it appears you have the primary GFI feeding the other receptacles "downstream" of the GFI, I would try disconnecting the last receptacle first and then work backwards toward the GFI. Something appears to have changed to cause these nuisance trips.

Also had a case of nuisance trips with moisture in the conduit feeding an outlet near a swimming pool. Here is where you truly want GFI protection.
Much like your case, everything was fine for a year or so.

Used a megger on the wires and found lower resistance than normal.

Turns out there was a little water in the conduit causing leakage to ground tripping the GFI. Ran an air hose in the conduit for a day to dry it out and resealed the joints. Fixed the problem.

One thing I still wonder about is that wire pulling lube is water based and somewhat conductive. Seems to me this would be self defeating.
Or have the manufacturers come up with a new formula.

good luck

[nocheepgas]

nocheepgas,


Since it appears you have the primary GFI feeding the other receptacles "downstream" of the GFI, I would try disconnecting the last receptacle first and then work backwards toward the GFI. Something appears to have changed to cause these nuisance trips.

I had already tried disconnecting all downstream receptacles, no luck

Also had a case of nuisance trips with moisture in the conduit feeding an outlet near a swimming pool. Here is where you truly want GFI protection.
Much like your case, everything was fine for a year or so.

Moisture may be the culprit, as we have had a much wetter year than in the past, however the sub panel is indoors and the first (GFI) receptacle is att he building entrance, under the eave and all conduit is under roof and concrete.

Thanks for the responses. I'll try blowing some air through the conduit with my shop vac. But I was also wondering if placing a GFI breaker in the panel instead of at the receptacle would have any effect?

[6010]

If you haven't found the problem yet then disconnect all the receptacles down stream from the first ( GFI) receptacle by disconnecting the load side of the GFI. With all the other receptacles disconnected if the GFI won't reset then you either have the GFI wired incorrectly or you have a bad GFI receptacle. If you can reset the GFI and run a load from it OK, then your problem is on down the line. It could be a wire touching the conduit, a bad receptacle, moisture, etc. It is now hunt and peck until you find it. I don't think a GFI breaker will help unless there is something wrong with the GFI receptacle. They both serve the same purpose.

You mentioned you have conduit run under the concrete. I have seen conduit run under concrete fill up with ground water. You may end up having to pull this wire out and inspect it and maybe end up running new wire, possibly wire with moisture resistant insulation.

[6010]

I meant to tell you that you do not have to worry about your wire feeding your sub panel as being the problem. A GFI breaker only protects ( trips ) on faults resulting from what is plugged into it or downstream wiring or loads. As long as you have the correct voltage in the panel feeding the line side of the GFI, then you can rule out it as a problem. Please let us know when you find it, you have my curiosity up

[nocheepgas]

Problem Fixed!

Permanently, I hope! I did notice that the "new" receptacle I purchased did not come with any stickers for other protected outlets, and it didn't have any yellow tape over the "load" connections as the instructions indicated. So just by chance I took it back to the Depot and got a new one. This one seems to work fine!
Now what were the chances I would have purchased a defective one to replace a defective one?

[kevin]

the depot

if i need electrical stuff, your local electrical store is a better choice, more experienced people, i had problems with gfi recepticals, i removed them all, i have a few trucks that have inline radiator hose heaters in them, they are plow trucks, every time i plug 1 into a gfi, it trips, i also have 2 rock crawlers, 1 jeep, 1 scout, they also have these type heaters, they also trip gfi. across the street from me, my sister just built a new house, gfi,s every where, i broght my fleet of heaps to her house to check the gfi to heater thing, same result, trips breaker, i also used many extension cords, to this date, i cant figure out why they trip

[Sberry]

Heating equipment tends to trip them, I think it might be leakage from elements. I think there is a code allowance for heating, there are special gfci rated at 30MA just for it. I might get a couple but as of now just wired a couple outlets ahead of the gfi's just for block heaters.

[6010]

Sometimes extension cords can introduce enough inductance to interfere with the proper operation of the GFI causing nuisance tripping. Two things you can do to help with this problem is use the shortest extension cord you can get by with, and do not have any of it coiled. Spread the extension cord out so the coils are not lying on top of each other.