GFCI testing

[Charlie Bob]

I have one of them receptacle testers, one with a button in the middle to test GFCI receptacles and breakers.

I've always used it and always worked fine. Last night i finished wiring about 10 circuits at a Gym, some with GFCI breakers and some with GFCI receptacles protecting other receptacles downstream.

The tester failed to trip the GFCI recep. like it always done before.

I Thought the thing was bad i went to get another one today, and it did the same thing. It just failed to trip the GFCI recep. I tried it out at home as well, and nothing.

The receptacles work just fine, they trip and reset just fine, cutting the power to the downstream receptacles.

My inspector uses the same tester to check receptacles and i'm afraid he'll try to tell me there's something wrong with my wiring and fail me.

Any ideas? Has this ever happened to you?

thanks.

 

[infinity]

Try testing them with a solenoid type (Wiggy) tester from hot to ground. If properly wired and functioning it will trip every time.

 

[shepelec]

I failed an inspection because of an old tester. I was able to test all of the GFCI's fine but when the inspector walked through he told me none of the worked and "oh yeah it will cost you a reinspection fee".

I bought him a new tester and I did not have to pay the fee.

They do wear out try a new one.

 

[Charlie Bob]

I failed an inspection because of an old tester. I was able to test all of the GFCI's fine but when the inspector walked through he told me none of the worked and "oh yeah it will cost you a reinspection fee".

I bought him a new tester and I did not have to pay the fee.

They do wear out try a new one.

I did. I just bought it today. It did the same thing.
So i can rule the tester out. The weird thing is that shows correct wiring and the button on the GFCI is tripping the recep, and the reset button works as well.

 

[Charlie Bob]

Try testing them with a solenoid type (Wiggy) tester from hot to ground. If properly wired and functioning it will trip every time.

thanks i'll try that.

 

[Buck Parrish]

It sounds like your equipment ground is not their or open.
But you would have said, so it must not be that.

 

[Volta]

Most plug in gfci testers will drain to the egc, so if it isn't present the device won't trip. The button on the gfci will still do it though.

As far as I know, the only correct means of testing the full operation of a gfci is the test button. Plug in types may activate the mechanism, but that does not prove that the device is still within specs.

If the resistance of the portable tester were reduced by some foriegn matter like oily residue, or dirt, or spilled soda, when used it might activate the gfci, but may be passing more than 6 ma of current. The test would not confirm that the circuit would deenergize at the designed 4 to 6 ma.

I only use them to determine which gfci protects a receptacle, for true testing for safety I use the device 'test' button only.

 

[Charlie Bob]

This is weird. The lengths are short, about 20' (the longest) and less.
Everething is bonded (Boxes ), I use EMT for raceway, and these testers would not trip anything at all. ( 6 gfci recep. feeding other recep. and 5 gfci breakers).
There's a egc run in the raceway.

 

[LarryFine]

Suggestion: plug your tester into a 3-wire ground "cheater" adapter (or a receptacle and plug with the receptacle's EGC not run to the plug), with the green wire extended to a known ground.

If it works now, you'll know the circuit's EGC is bad. The wiggy line-to-ground will also work. It's possible the tester somehow isn't 'compatible' with the GFCI devices.

 

[Charlie Bob]

Suggestion: plug your tester into a 3-wire ground "cheater" adapter (or a receptacle and plug with the receptacle's EGC not run to the plug), with the green wire extended to a known ground.

If it works now, you'll know the circuit's EGC is bad. The wiggy line-to-ground will also work. It's possible the tester somehow isn't 'compatible' with the GFCI devices.

Thanks Larry, i'll try that.
But how the EGC can be bad? It's It's brand new wire.
And this tester should work even without a ECG in the line, since GFCI don't really need a EGC to work properly. Am i missing something.

 

[Volta]

GFCI's don't need the EGC, but external testers do.

 

[480sparky]

Thanks Larry, i'll try that.
But how the EGC can be bad? It's It's brand new wire.
And this tester should work even without a ECG in the line, since GFCI don't really need a EGC to work properly. Am i missing something.

A bad splice.

I have also run across new conductors that just aren't complete between point A and point B.

 

[Charlie Bob]

GFCI's don't need the EGC, but external testers do.

I see. Thanks.

 

[Charlie Bob]

A bad splice.

I have also run across new conductors that just aren't complete between point A and point B.

I hope that's not it.Everything is stranded wire, i made sure it was tight and good.

 

[gar]

100213-2151 EST

The internal test resistor in a GFCI is 15,000 ohms. At 120 V this is a test current of 8 MA.

Buy a 15,000 1 W carbon composition resistor. Use this as your external GFCI test from hot to a known good ground, maybe the neutral bus at the main panel if nothing else works. Make sure the test is to the hot wire.

If you can not externally prove that the GFCI will trip, then take one to your shop and test it there. If it works at your shop on the bench with an external 15000 ohm resistor, then you have to look for problems at your job site.

If you can not easily get a 15 k resistor in a 1 W rating it is probably OK to use a 1/4 W which you might get at a Radio Shack if you do not have access to better electronic supply houses.

..

 

[don_resqcapt19]

Most plug in gfci testers will drain to the egc, so if it isn't present the device won't trip. The button on the gfci will still do it though.

As far as I know, the only correct means of testing the full operation of a gfci is the test button. Plug in types may activate the mechanism, but that does not prove that the device is still within specs.

If the resistance of the portable tester were reduced by some foriegn matter like oily residue, or dirt, or spilled soda, when used it might activate the gfci, but may be passing more than 6 ma of current. The test would not confirm that the circuit would deenergize at the designed 4 to 6 ma.

I only use them to determine which gfci protects a receptacle, for true testing for safety I use the device 'test' button only.

The resistor in the device it self is sized to flow 8 to 10 mA at 120 volts. It does not verify the correct trip range. It does exactly what the plug in tester does.

 

[LarryFine]

Am i missing something.

There is one remote, but theoretically-plausible answer: the supply's main bonding jumper is missing.

 

[ELA]

The resistor in the device it self is sized to flow 8 to 10 mA at 120 volts. It does not verify the correct trip range. It does exactly what the plug in tester does.

Not exactly...
Inside the GFCI's that I have examined a 15K test resistor gets connected between the load side neutral and the line side hot lead, thus creating the current imbalance. They do this so as not to be dependent upon the EGC being present.

So as already has been stated the external tester is different from the internal test in that it does rely on the EGC.


Gar has suggested one test. Another is to use the resistor he stated and connect from the load side of the GFCI neutral to the line side hot (just like what is inside the breaker).

Please be careful if you do this though.

 

[Volta]

The resistor in the device it self is sized to flow 8 to 10 mA at 120 volts. It does not verify the correct trip range. It does exactly what the plug in tester does.

If by correct you mean 4 ot 6 ma, ok, I can believe that if they are designed slightly higher, though I don't know why the resistor value would be high enough that 6 ma wouldn't flow. Seems like a poor test, IMO.

But that isn't what matters. My point is that any resistance below that designed for will likely cause the unit to trip. If the portable unit trips the device no gaurantee can be given that the installed device will trip within to 4-6 range if proper operation of the tester hasn't been verified.

 

[gar]

100214-1817 EST

Volta:

We know what the resistance value is inside the GFCI for the test resistor. It is 15,000 ohms, and quite close based on the ones I have measured.

15,000 ohms results in the following currents:
130 V 8.7 MA
110 V 7.3 MA
090 V 6.0 MA

The test resistor has to be designed so that at low line voltage the current will exceed at least the high spec limit of the GFCI. Looks like the resistance choice is good.

Also note there is an inverse time characteristic to the trip time vs current curve.

.