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Old 11-12-2011, 08:48 PM   #1
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GFCI troubleshooting


Hello all!

I am a new member and this is my first post, thank you for the privilege to participate in your forum.

I have a question about troubleshooting a GFCI issue.

I have "inherited" this property with a half-finished detached garage and I am trying to fix and rent or sell it.

The garage has one electrical line coming from a 20A fuse in the circuit breaker in the house over 12 gauge wires, so that's good.

However, I went to test two GFCI outlets found in two opposite walls of the garage and here's what happens with both of them.

With a load -say a lamp- plugged in, pressing the black TEST button the current is interrupted (as it should) and by pressing the red RESET button the lamp is ON again.

That's normal you'd say and I agree this is how it should work.

But I took it a step further and I tested again with one of these circuit testers by Sperry Instruments.

Here's what I got:

Checking the outlet wiring gets a pass, or two orange lights (for those familiar with the device).

Testing the GFCI though by pressing the black button (the one on the tester now) does not NOT result in the GFCI tripping the circuit (as it should) and the lamp is still lit. However, with the tester's black test button pressed, the indicator lights now changed, reporting a HOT/NEUTRAL reverse!? Letting the black test button go, results in the tester reporting that the outlet wiring is correct, again.

I tested the same way with all other GFCI outlets inside the house (this garage is getting power from) and the tester works as expected: On a properly wired GFCI outlet, pressing the tester's black test button results in the GFCI tripping the circuit exactly as if you pressed the black test button on the GFCI itself.

Sorry for the detailed description, I am just trying to be clear about all this, hopefuly I did not bore you.

Basically both GFCI's appear to be working fine, their internal testing works as expected and their wiring appears to be correct. However, using this tester gives me erratic results, from the GFCI not tripping to the outlet itself being (momentarily only) wired backwards.

Any ideas, why this is happening and how to fix it? We are doing some other major work to this house (e.g. not electrical) before we can rent or sell it, all permits have been issued and an inspector is scheduled to come after all repairs, etc, are complete. I am not sure if an inspector will ask to test some electrical aspects of this house (and garage) even though no (major) electrical work is being done and no such permits taken?

No offense to all professional electricians out there but I'd like to avoid having to hire a licensed electrician for something that -at least to me- appears to be simple(?) but again, I do not want to take any chances myself.

Thank you very much in advance for your input!

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Old 11-12-2011, 08:52 PM   #2
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GFCI troubleshooting


If you have not pulled them from the junction boxes to verified how they are wired, that is the one thing that you are leaving out. Never trust another person's wiring skills.

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Old 11-12-2011, 08:58 PM   #3
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Those testers work by connecting the ground and neutral.
Without a proper ground connection, the tester will not work.

Make sure that you have a grounded circuit from the house to the garage.
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Old 11-12-2011, 08:59 PM   #4
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You mention the pedigree of the working GFCI. What's the source(s) of the ones that are at issue?
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Old 11-12-2011, 09:20 PM   #5
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WOW! You guys are amazing, thank you all very much for the prompt responses !

Yes, I did pulled them out and they seem to be wired fine. I mean a black (hot) wire to the gold screw and a white (neutral) wire to the other. There is no green (ground) wire but I am assuming the ground works fine since 1st the outlet tested-out fine with the Sperry tester and there should be a connection to ground via the mud-ring, box, tube conduit, etc., right?

I was under the impression that GFCI works by detecting (even the slightest amount of) current going through the ground, but I can be wrong. Anyway, the tester works as expected with all other house GFCI but fails with the garage. I am starting to think that -indeed- there is something wrong with the ground ... but what?

I am not sure I understand what "the pedigree of the working GFCI" is but the source of both GFCIs is (only) one 120V line coming from the house via what appears to be a 35 ft. metalic pipe burried in the ground.

--

Guys, if the grounding is not "proper" how come the Sperry tester says it is?

Last edited by XwpisONOMA; 11-12-2011 at 09:57 PM.
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Old 11-12-2011, 10:05 PM   #6
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Quote:
Originally Posted by XwpisONOMA View Post
I am not sure I understand what "the pedigree of the working GFCI" is but the source of both GFCIs is (only) one 120V line coming from the house via what appears to be a 35 ft. metalic pipe burried in the ground.
The pedigree is the total wiring list of the working GFCI.
You say there are 3 GFCI's in the garage.
Are they all on separate breakers?
Wired directly to the garage?
Are the GFCI's wired to the line or load terminals?
You can't have 2 GFCI's on the same line. That might be the issue.
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Old 11-12-2011, 10:16 PM   #7
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ΟΚ, Ι see!

There is only one line coming from the house electrical board to the garage. This is a 12 gauge wire protected by a 20A fuse. Line comes in, then splits in two, one feeds GFCI #1 on one side and the second one feeds the garage door mechanism and eventually GFCI #2 on the other side of the garage. Both GFCI use the load connections to feed a couple more normal (not GFCI) outlets on the other two walls. Of course these cascaded outlets from GFCI #1 and #2 do not eventually connect to each other at the end, or there would be a problem

I can tell you that. I did not do the wiring but I have to figure out why the tester fails the GFCI. If I read your feedback right, YES, there is ONE line coming in, then there is a Y split that feeds two GFCIs. So yes, there are two GFCIs on the same line, but not one fed by the other from the load connections. Is this what you are asking me? On a different note, is is possible that the burried pipe is not somehow providing a "proper" grounding? But again how come the tester says there is proper grounding but fails the GFCI. I am sorry, is this crazy or what?

Thanks again for the imput!

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Old 11-12-2011, 10:24 PM   #8
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GFCI troubleshooting


If you have multiple GFCI's, they should be wired in "parallel" using just the line side. Or if a regular outlet wired off a GFCI, then THAT would be connected to the load side.

And if you have a regular outlet tester, see if it shows a good ground on those outlets. Or use a multimeter set to AC voltage 200 or 250 volts. Hot to ground should read around 120/115/110 volts. The same as hot to neutral.

Here is a diagram of how multiple GFCI's should be connected.
Note: This diagram shows the line wires at the top, however the GFCI's I use have the line connections at the bottom. But anyway notice the load connections are not used from one GFCI to the next GFCI, but are for the last "regular" outlet.

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Old 11-12-2011, 10:29 PM   #9
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There should be 3 wires from the house. Hot (typically black), Neutral (typically white), and ground (typically green or bare).

In some areas a metal conduit pipe is allowed for the ground, but those can come loose and you lose the ground connection.
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Old 11-12-2011, 10:42 PM   #10
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Yes, this is how it is wired in my case too, only I have two GFCIs.

Actually each GFCI then "feeds" one standard (normal) outlet from the "load" connections and then (with parallel wiring of course) one more (last one) std. outlet.

Here's a crude but accurate schematic:

120V (20A fuse)
----------------
|
|
V
|
|-->--SPST switch-->--Ceiling Lights
|
|-->--GFCI#1-->--(via load)-->--Std. Outlet #1A-->--Std. Outlet #1B
|
|-->--GFCI#2-->--(via load)-->--Std. Outlet #2A-->--Std. Outlet #2B
|
|-->--Garage Door mechanism-->--outside motion sensor lights


I am not a certified, licensed electrician but this is a darn simple circuit and something is goofy with it. I will probably have to sleep on it and "attack" again tomorrow.

Thanks for the input!
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Old 11-12-2011, 10:48 PM   #11
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Quote:
Originally Posted by Billy_Bob View Post
There should be 3 wires from the house. Hot (typically black), Neutral (typically white), and ground (typically green or bare).

In some areas a metal conduit pipe is allowed for the ground, but those can come loose and you lose the ground connection.
I think this is the culprit, I mean it's the only logical explanation. I will run a long wire from the garage to a known good ground point in the house and I will test again. If it works then, the buried conduit provides a ground good enough for the Sperry tester BUT not for the GFCI tripping circuit.

I can't come up with a better explanation and it's getting late here in the Midwest. Hmm, new day, fresh brain ...

Thank you all for running to the rescue, I am much obliged!

Last edited by XwpisONOMA; 11-12-2011 at 10:50 PM.
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Old 11-12-2011, 10:52 PM   #12
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I'm thinking there is a poor or broken ground.

To test a GFCI with an external tester, it relies on the ground connection. The internal test switch on the GFCI works differently. Here is a diagram of that...


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Old 11-12-2011, 11:01 PM   #13
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WOW! Thanks, this is impressive.

I thought GFCIs work by measuring current "escaping" through the ground, but it actually does it by comparing the amount or current flowing through the HOT and NEUTRAL. In a normal situation you have the same amount in both but if a fault exists (e.g. some or all current escaping to ground) then there is a discrepancy which is measurable and once detected trips the shunt.

So do you think that running a long wire from the receptacle to a known good ground in the house and testing again will solve the mystery? If that's the case I will have to run a green ground cable from the house electric board to the garage, provided that the path underground is still intact, right?

Thanks!
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Old 11-12-2011, 11:41 PM   #14
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Mystery solved: The ground was not good enough.

Like I said, I run a long wire to a known good ground point in the house and using the external tester tested again this time with the expected results.

GFCI tripped, breaking the circuit and not producing erroneous results with the tester. Whoever build the garage did not bother running a 3rd (green) ground wire, relying on the conduit to provide that. Somehow the conduit fails to do that. The Sperry tester says my grounding is OK but if I needed the GFCI to save my life it would n't because of the inadequate grounding.

I guess I am going to call the company tomorrow (well Monday) and tell them they sold me a tester for $5.99 that -under the right (i.e. wrong) circumstances- could have cost my or somebody's else's life.

Thank you all for helping out. To do so on a Saturday night and so quickly and efficiently, well my friends, this is commendable. God bless the USA!

Thank you all so very much!

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Old 11-12-2011, 11:50 PM   #15
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Quote:
Originally Posted by XwpisONOMA View Post
WOW! Thanks, this is impressive.

I thought GFCIs work by measuring current "escaping" through the ground, but it actually does it by comparing the amount or current flowing through the HOT and NEUTRAL. In a normal situation you have the same amount in both but if a fault exists (e.g. some or all current escaping to ground) then there is a discrepancy which is measurable and once detected trips the shunt.


Thanks!
*BINGO* RIGHT ON THE MONEY !
Thats exactily how they work !
They are technically known as "core balance relays"
The original earth leakage breakers did work
by monitoring the currents in the earth line,
But they dont use that old system any more,
but the term "earth leakage breaker" has stuck around !
even thou they are really core balance relays now !

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