GFCI trips with barely any load

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Old 04-27-10, 01:03 PM
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Question GFCI trips with barely any load

I recently finished 1/2 of my basement, and used conduit to run the electric. I have 2 separate runs, 12 gauge wire, each run hooked to a different 20 amp breaker. I have a 15 amp GFCIs wired to the start of each run.

The rest of the basement is partially wired, but no GFCIs are there. The first problem was with a halogen stand-alone light I use for working in dark corners... it kept tripping the GFCI. I could plug it into a different outlet in the basement that was on a 15 amp breaker and it worked fine. I changed out the GFCI to ensure I didn't have a defective one and the same thing happened.

The other day someone pulled an extension cord out of the other run, on a different breaker, and the GFCI tripped. What's going on? I can run a dehumidifier or shop vac in either run of outlets without a problem. I've checked that the neutral wires were in the right places and that the grounds were working. Any ideas?
 
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Old 04-27-10, 01:09 PM
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It sounds to me like there's a defect in the extension cord or the work light.
 
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Old 04-27-10, 01:36 PM
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Are you certain you hooked the incoming power to the "line" terminals of the GFCI and the outgoing run the the remainder of the receptacles on each circuit to the "load" terminals of the GFCI?

GFCIs can act very funny if you reverse the two.

The possibility of defect in the wiring of the light and extension cord is also true, but both being defective is a touch unlikely, IMHO.
 
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Old 04-27-10, 08:52 PM
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Question

I have checked the wiring of the shop light since this first happened. (it's on a stand, so I took it apart). I thought, too, that it was maybe time to retire it. Any idea why it would trip the GFCI but not a 15 amp breaker anywhere else in the house? Just sensitivity?

As far as the extension cord - I wasn't here to witness that one. A three prong that they had been using on some music equipment, and all was well until they stopped for the afternoon and pulled the cord out.

I did check to make sure the "line" and "load" terminals were right (when I swapped the one out). The halogen trips it regardless if it's plugged into the actual GFCI or an outlet down the line.

Do I trash the light and call the extension cord a fluke? I've never seen one blow a breaker on it's way out. (?). It worries me if that work light is drawing enough to trip that outlet. But the fact I've used it all over the house and garage and have never tripped a 15amp breaker confuses me.

What would be a good way to test the load without wrecking anything? I would think the shop-vac or the dehumidifier would have drawn more. We've also run a space heater from that same outlet. Was it a mistake to put 15 amp GFIs on a 20 amp circuit? or only if there's eventually enough equipment plugged in where I need the extra amperage? It's pretty sparse down there yet. Nothing on the one run, and a computer, stereo, and guitar amp on the other.

Sorry my questions are interspersed here. Please let me know if any of you have any ideas of what I could test.

Thank you!
 
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Old 04-27-10, 08:57 PM
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What would be a good way to test the load without wrecking anything? I would think the shop-vac or the dehumidifier would have drawn more. We've also run a space heater from that same outlet. Was it a mistake to put 15 amp GFIs on a 20 amp circuit?
Remember, a GFI is not an overload protection device.
 
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Old 04-27-10, 09:25 PM
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Originally Posted by CasualJoe View Post
Remember, a GFI is not an overload protection device.
and even though ground is in its name, the ground actually has nothing to do with a GFI operating properly. It works with the hot and neutral connections. It trips by sensing an imbalance between hot and neutral.
 
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Old 04-27-10, 09:32 PM
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What brand the RCD { GFCI } you are using due some brand are pretty senetive to tripping for no reason.

I know you did double check the line and load connections however when you push the RCD back in the junction box make sure you don't let the netural conductor strand touch the ground { bare } conductor at all otherwise it may cause early tripping.

Is this basement is pretty dry or kinda little damp ??

If the latter the humity can play hovac on them.

Merci,Marc
 
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