GFCI Tester

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wirebender

wirebender

Senior Member
Location
North Central Texas
I was checking receptacles with one of these:


41B64D0RT4L_SL500_AA280_.jpg


A receptacle (not GFCI) with a MWBC (12/3) made all three lights come on. If I touched my knee to the floor while holding the strap of the receptacle the red light went out.

Everything was properly wired.

Receptacles downstream showed to be okay.

Why the three lights?


At a GFCI receptacle in another location my tester would not trip the GFCI or any downstream receptacles.

I only read 103 volts hot to egc at the GFCI.

What do I need to look for on this?
An open ground upstream?
 
B

Bill W. 1

Member
Location
Pleasanton Ca.
Try tripping and resetting the gfci once or twice and re test with your tester.
I have had various symptoms (mainly opens) be resolved by exercising the
gfci.
Other than that, very strange because there should be no red light unless
there is current from gnd. or neut. to the ungrounded slot (reversed polairity).



Inspect the uninspected
 
B

Bill W. 1

Member
Location
Pleasanton Ca.
You could also try of course a wiggy,solonoid type tester that should trip your
gfci (although not at correct current level) if you test from hot to ground.


Inspect the uninspected
 
wirebender

wirebender

Senior Member
Location
North Central Texas
Bill W. 1 said:
Try tripping and resetting the gfci once or twice and re test with your tester.
I have had various symptoms (mainly opens) be resolved by exercising the
gfci.
Other than that, very strange because there should be no red light unless
there is current from gnd. or neut. to the ungrounded slot (reversed polairity).



Inspect the uninspected
Click to expand...

I have set and reset. Polarity is good.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Tony, it's time to break out the extension cord.

Plug a 3-wire cord into a known-properly-wired (and non-GFCI'ed) receptacle, and use a solenoid-type tester ("wiggy") to check voltage between the cord's hot and the receptacle-under-test's neutral slot and EGC hole.

You can also test between the receptacle's hot slot and the cord's neutral and EGC to compare to the receptacle's neutral and EGC. But, the first test is most revealing; using a solenoid tester (or lo-Z meter) is a must.
 
C

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
I don't really care for these testers. I'd rather use my regular Fluke T+ Pro or Knopp to test receps and GFI's. A regular meter will tell you all you need to know without having to decipher what the lights mean on one of those testers.

Which makes me wonder, did you try your regular meter after checking with this tester?
 
wirebender

wirebender

Senior Member
Location
North Central Texas
Cow said:
I don't really care for these testers. I'd rather use my regular Fluke T+ Pro or Knopp to test receps and GFI's. A regular meter will tell you all you need to know without having to decipher what the lights mean on one of those testers.

Which makes me wonder, did you try your regular meter after checking with this tester?
Click to expand...


Yes.

I was only using this to check all the receptacles on a job we are finishing. You know, testing to make sure they were all wired correctly and tight to the wall. You can't beat these for that.
 
e57

e57

Senior Member
Location
San Francisco, CA
wirebender said:
I was checking receptacles with one of these:


41B64D0RT4L_SL500_AA280_.jpg


A receptacle (not GFCI) with a MWBC (12/3) made all three lights come on. If I touched my knee to the floor while holding the strap of the receptacle the red light went out.

Everything was properly wired.

Receptacles downstream showed to be okay.

Why the three lights?
Click to expand...
I had one of these MANY years ago - puzzled me too....

I really can't remember exactly what it was - But I would go back with a few 500W halogen flood lights stick say two on one side of the 3-wire, and one on the other - wait ten minutes then put your meter to it - I think you have a loose neutral. You want to check it under an unbalanced load condition.


wirebender said:
At a GFCI receptacle in another location my tester would not trip the GFCI or any downstream receptacles.

I only read 103 volts hot to egc at the GFCI.

What do I need to look for on this?
An open ground upstream?
Click to expand...
This - coupled with your other debacle - I'm thinking you need to check feeder and service connections - Under load.... Disposable ones, like the halogen lamps I mentioned* - no lighting with dimmers... or other pricey stuff. Shut that stuff off.

You're just wrapping up a job - there's nothing really in the place yet - a fairly balanced set of lighting with nothing else and everything will seem just fine, but unbalance it once people move in could spell disaster.

*Other hearty loads capable of taking a high/low (Loose/lost neutral) condition like the one I think you have are space heaters or plain ol' 100w lightbulbs if you putt a bunch of them together. Start with a balanced and loaded condition on both phases and slowly start to unbalance it more and more - if I'm correct you'll get one with a lower voltage - one with higher. (And you can change this voltage with moving load from one leg to another.) If the loose connection is not totally obvious - as it will be normal on one side, and all screwy on the other - sometime it can be hard to find it in a panel because you might not measure with your leads in the right place, or the connection only weakens under a heavy load - you can find it under load with a IR thermometer. The bad connection will be hotter than the area around it...

Let us know....
 
B

Bill W. 1

Member
Location
Pleasanton Ca.
"I only read 103 volts hot to egc at the GFCI."

I guess if you read higher (normal) voltage from hot to neutral, that would
have to mean a very poor ground.

With no eq. ground available at the receptacle your GB tester won't trip a GFCI (although the test
button on the receptacle should still work).

Then, as others have said, maybe the tester is the culprit.

Happen to be familiar with that model GB tester and still tend to think the
only way to get a red light is with a hot/neut or hot/egc reversed, and we know that's not the case... so, gotta be the tester and not the TESTOR !(not actually a word).
 
e57

e57

Senior Member
Location
San Francisco, CA
Bill W. 1 said:
"I only read 103 volts hot to egc at the GFCI."

I guess if you read higher (normal) voltage from hot to neutral, that would
have to mean a very poor ground.

With no eq. ground available at the receptacle your GB tester won't trip a GFCI (although the test
button on the receptacle should still work).

Then, as others have said, maybe the tester is the culprit.

Happen to be familiar with that model GB tester and still tend to think the
only way to get a red light is with a hot/neut or hot/egc reversed, and we know that's not the case... so, gotta be the tester and not the TESTOR !(not actually a word).
Click to expand...
I have not had enough coffee.... But draw out the circuit of the tester on a 3-wire circuit, and see what it will take to get all 3 lights....

The neutral has a potential in reference to ground (or vise versa), but also the potentials H-N, and H-G are present as well.

And in the case of the GFI, using the tester applies a small load imbalance between H-N, by shunting some voltage away to ground through a resister. Without a solid neutral, or ground this tiny load is not creating enough of an imbalance H-N to trip the GFI, as it compensates the voltage from the other leg, or shunts it to deep space on the ground.

And this: "If I touched my knee to the floor while holding the strap of the receptacle the red light went out." This slight change in potential is enough to either have that light, or not. Sure it's an anomaly, but large enough to have a light or not. Either the ground is floating in respect to the hot, or the neutral is, but definitely in respect to each other... One is a shock hazard - the other is a fire hazard. IMO it's best to be prepared to seek and eliminate both.
 
wirebender

wirebender

Senior Member
Location
North Central Texas
e57 said:
I had one of these MANY years ago - puzzled me too....

I really can't remember exactly what it was - But I would go back with a few 500W halogen flood lights stick say two on one side of the 3-wire, and one on the other - wait ten minutes then put your meter to it - I think you have a loose neutral. You want to check it under an unbalanced load condition.


This - coupled with your other debacle - I'm thinking you need to check feeder and service connections - Under load.... Disposable ones, like the halogen lamps I mentioned* - no lighting with dimmers... or other pricey stuff. Shut that stuff off.

You're just wrapping up a job - there's nothing really in the place yet - a fairly balanced set of lighting with nothing else and everything will seem just fine, but unbalance it once people move in could spell disaster.

*Other hearty loads capable of taking a high/low (Loose/lost neutral) condition like the one I think you have are space heaters or plain ol' 100w lightbulbs if you putt a bunch of them together. Start with a balanced and loaded condition on both phases and slowly start to unbalance it more and more - if I'm correct you'll get one with a lower voltage - one with higher. (And you can change this voltage with moving load from one leg to another.) If the loose connection is not totally obvious - as it will be normal on one side, and all screwy on the other - sometime it can be hard to find it in a panel because you might not measure with your leads in the right place, or the connection only weakens under a heavy load - you can find it under load with a IR thermometer. The bad connection will be hotter than the area around it...

Let us know....
Click to expand...

Thanks, e57, I will check all that out. No AFCI, new skilled nursing home.
 
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