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Old 10-09-2008, 12:57 PM   #1
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GFI circuit advice needed


I'm doing the finish wiring in my garage. I have one GFI circuit which is fine until I plug something into it... then it trips.

I can have the entire thing wired and covered... even plug the tester into any of the plugs... and get two yellow lights. All is good right? .... WRONG. As soon as I plug my garage door opener or any other tool into the outlet... it trips. I don't even need to fire up the tool... just plugging it in sets it off.

Any ideas?? Bad GFI??

Whatchathink?

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Old 10-09-2008, 02:08 PM   #2
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GFI circuit advice needed


I had an issue yesterday where a GFI outlet tripped as soon as it got power. I had three-prong outlets on the circuit that don't have a ground but did have the neutral and ground jumpered. When I removed the connections between the neutral and ground the circuit worked.

My guess is you have a fault somewhere.

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Old 10-09-2008, 03:17 PM   #3
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GFI circuit advice needed


Check for contact between the bare ground and the neutral (white) on the load side of the GFCI.
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Old 10-09-2008, 08:59 PM   #4
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GFI circuit advice needed


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Originally Posted by jheavner View Post
I had an issue yesterday where a GFI outlet tripped as soon as it got power. I had three-prong outlets on the circuit that don't have a ground but did have the neutral and ground jumpered. When I removed the connections between the neutral and ground the circuit worked.

My guess is you have a fault somewhere.
J, several brands of GFCIs pop when power is first applied to them. Just having the neutral wired to a ground on an unused receptacle won't cause it to trip. However, a ground wire (all the way back to the panel) touching a neutral will. I think what you experienced was the pop when the receptacle was first energized. And most won't pop every time power is off then restored unless quite some time has gone by.
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Old 10-10-2008, 09:08 AM   #5
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J, several brands of GFCIs pop when power is first applied to them. Just having the neutral wired to a ground on an unused receptacle won't cause it to trip. However, a ground wire (all the way back to the panel) touching a neutral will. I think what you experienced was the pop when the receptacle was first energized. And most won't pop every time power is off then restored unless quite some time has gone by.
You know, that's interesting because we couldn't get the thing to stay on. We removed the line going downstream from it and it worked ok but as soon as we connected it, it popped. We then went to what we thought was the next receptacle is series, disconnected the downstream line, cut the ground/neutral jumper, and it worked. Based on that we just assumed that was the problem and went through and cut the jumpers. If what you're saying is right then at least one of my outlets somewhere has a ground, right? Is there a fool-proof way of determining if an outlet is really grounded correctly? That wouldn't help me though in grounding my other outlets though would it? I can't pull a separate ground wire.
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Old 10-10-2008, 09:20 AM   #6
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Is there a fool-proof way of determining if an outlet is really grounded correctly?
Just get an inexpensive receptacle tester that plugs in and lights up. If there's an open ground in a receptacle, the lights' pattern will indicate it.
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Old 10-10-2008, 09:27 AM   #7
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Just get an inexpensive receptacle tester that plugs in and lights up. If there's an open ground in a receptacle, the lights' pattern will indicate it.
But this will not give you an indication of a bootleg ground, which is what you have found on your receptacles. You need to manually check all your receptacles for proper ground.
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Old 10-10-2008, 09:57 AM   #8
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GFI circuit advice needed


What country do you live in? As far as I know, here in the US, neutral is never supposed to be connected to ground, except at the main panel.
I have heard of it being done by some DIYers, and the tester will report a good circuit, as they don't know the difference.

Is your GFCI wired correctly?
Check the line/load connections. You must have your downstream line and neutrals connected to the LOAD side of the GFCI.

Also, GFCI will still work without a ground, but if the neutral is bonded to ground at any point, you may get an imbalance of current between line (hot) and neutral, and the GFCI will trip, as it is supposed to.

You should be able to tell if you have any connections between neutral and ground with an ohmmeter (with power turned off of course). You need to disconnect the LOAD side of the GFCI, and test the downstream receptacles, neutral to ground should be open.
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Old 10-10-2008, 10:11 AM   #9
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You know, that's interesting because we couldn't get the thing to stay on. We removed the line going downstream from it and it worked ok but as soon as we connected it, it popped. We then went to what we thought was the next receptacle is series, disconnected the downstream line, cut the ground/neutral jumper, and it worked. Based on that we just assumed that was the problem and went through and cut the jumpers. If what you're saying is right then at least one of my outlets somewhere has a ground, right? Is there a fool-proof way of determining if an outlet is really grounded correctly? That wouldn't help me though in grounding my other outlets though would it? I can't pull a separate ground wire.
It seems that you are either have a ground fault in an outlet, or a ground fault through something plugged into an outlet. If you have a bootleg ground, then that by itself, without a connection to anything else, won't cause a trip. See the pic.
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Old 10-10-2008, 10:53 AM   #10
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I'm in the US and I have one of those handy plug-in testers but it will absolutely not detect if neutral/ground are bonded and will report a ground in that instance. A ground fault seems possible given the age of the wiring and some of the other "mysteries" I've uncovered but the problem did go away when I broke the ground/neutral connections that I could see in the other receptacles.

I think my $12 multimeter is junk (yeah, yeah, I know) and it's time to get a better model because while it will detect voltage (most of the time) it will always give an error when testing continuity, even if I touch the leads together.

Yes, I deserve to be flamed for buying a $12 multimeter.
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Old 10-10-2008, 10:57 AM   #11
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I think my $12 multimeter is junk (yeah, yeah, I know) and it's time to get a better model because while it will detect voltage (most of the time) it will always give an error when testing continuity, even if I touch the leads together.

Yes, I deserve to be flamed for buying a $12 multimeter.
Try changing the battery
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Old 10-10-2008, 11:10 AM   #12
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I'm in the US and I have one of those handy plug-in testers but it will absolutely not detect if neutral/ground are bonded and will report a ground in that instance. A ground fault seems possible given the age of the wiring and some of the other "mysteries" I've uncovered but the problem did go away when I broke the ground/neutral connections that I could see in the other receptacles.

I think my $12 multimeter is junk (yeah, yeah, I know) and it's time to get a better model because while it will detect voltage (most of the time) it will always give an error when testing continuity, even if I touch the leads together.

Yes, I deserve to be flamed for buying a $12 multimeter.
Hey thats ok, mines several years old but gets the job done. one of the leads broke, so I soldered 18awg wire to it....until I get it fixed.....
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Old 10-10-2008, 11:11 AM   #13
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Yes, I deserve to be flamed for buying a $12 multimeter.
No, you should only be flamed if you do any electrical troubleshooting and you DON'T have a multimeter. As was suggested, change the battery. Then rapidly cycle through the switch functions several times, and make sure the leads are good. The test that KE2KB suggests should show whether or not a ground fault exists. There should be nothing connected or plugged into the circuit when you do the test. Test between hot and neutral. There should be no reading. If there is, something is connected. Test between hot and ground. There should be no reading. You may have to get a known ground from dragging an extension cord with you, because there is no ground on the circuit you are testing. If there is continuity, you have a leak. This leak may not trip a normal breaker, only a GFCI.

I have found hot to ground leaks usually occur in wet places, such as outside receptacles. Not enough to trip a breaker, but plenty for the GFCI. Check from neutral to ground. There should be no reading.

This should be done from the load side of the GFCI with the conductors disconnected from the source.

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