Testing ungrounded receptacles on GFCI circuit

[MD84]

I am not seeing the diffreance in what Leviton recomends




You can test 'more' but only the manufacturers recommend test will count for anything.


(Still want to know what miswire this will not catch that your method will)

(c) If you installed your GFCI using step 7B press the TEST button, then plug
a lamp or radio into surrounding receptacles to see which one(s), in
addition to the GFCI, lost power when you pressed the TEST button. DO
NOT plug life saving devices into any of the receptacles that lost power.
Place a "GFCI PROTECTED OUTLET" sticker on every receptacle that
lost power, then press the RESET button to reset the GFCI.

The test you recommended will catch any miswire I can think of. The test you recommend is not the same as the one you quoted from Leviton. As highlighted in red Leviton states to FIRST press the test button THEN check downstream receptacles for loss of power. Leviton never instructs to plug anything in to the protected downstream receptacles while they are powered. Do you agree it is different?

If you only followed the instructions provided by Leviton it would be possible to not catch a miswire. The problem would soon be realized but not by the manufacturer recommended test.

 

[mopowr steve]

Ok in the case of a hot to ground short, yes the GFCI will see a current imbalance but it will be seeing this at exactly the same time as the breaker sees an overload condition.

There is no reason to think a GFCI can physically open the circuit faster than the breaker, that is not the purpose of GFCI.

Yeah, you would have to compare the responce time curves between the gfci recept and breaker if you knew what the fault current level was.

And I too would want to believe that the gfci would trip first but obviously that is not the case.

 

[ptonsparky]

I used to test the trip current on GFCIs by putting One probe in the neutral slot and series through my Fluke VOM then catch the max amps to the EG. Never entered my mind to use the hot side, at least not on purpose. Neutral to EG faults always trip a GFCI so why use any other?

These tests were for my edification.

 

[mopowr steve]

Yeah, I would rather do the neutral to ground fault versus a intentionally forced hot to ground fault even if it is just a 15/20 branch circuit.

 

[just the cowboy]

#10 melting

#10 melting

I wont criticize the method other than to say that breakers dont always trip, and you might be surprised to see what kind of arc can come out of a 12 or 14ga wire.

See that, one time when I was an apprentice I tried the " short out the circuit to find the breaker". I used a number 10 wire and pushed into the recticipcial, well it melted down and kept melting. Never found the breaker JW came and change circuit hot.

 

[GoldDigger]

See that, one time when I was an apprentice I tried the " short out the circuit to find the breaker". I used a number 10 wire and pushed into the recticipcial, well it melted down and kept melting. Never found the breaker JW came and change circuit hot.

Sounds like the reason you could not find the breaker was that there wasn't one! (Circuit illegally tapped off a higher current circuit, for example.)

 

[user 100]

Sounds like the reason you could not find the breaker was that there wasn't one! (Circuit illegally tapped off a higher current circuit, for example.)

I agree-

A higher current circuit-like the poco circuit :happyyes:- and tapped off the main lugs.

The "relief" would only come when the ckt burns itself open.

 

[prayerpartner212]

Question about the operation of the small plug in testers?

Question about the operation of the small plug in testers?

Do the small plug in type testers simply put a small load on the GFCI circuit and then short neutral to ground????

 

[user 100]

Do the small plug in type testers simply put a small load on the GFCI circuit and then short neutral to ground????

No- basically the plug in tester causes a short between the hot and egc when plugged into the gfci causing it to sense a ground fault and trip (maybe another member will chime in with the longer, better explanation /description). This is an important detail w/ these testers- they won't work on a ckt w/ no egc.

 

[GoldDigger]

No- basically the plug in tester causes a short between the hot and egc when plugged into the gfci causing it to sense a ground fault and trip (maybe another member will chime in with the longer, better explanation /description). This is an important detail w/ these testers- they won't work on a ckt w/ no egc.

There are no "shorts" involved in the testing, and no background load on the circuit is needed (as would be the case for an AFCI.)

All the plug in tester does is take some current (~10ma) from the hot and run it through a resistor to the EGC. That creates an imbalance in the current through the sensing coil since it is not returning through the neutral.
The built in test button has access to both sides of the coil, so it can draw current through a resistor from the hot lead on the receptacle side of the coil to the neutral lead on the line side of the coil.
A plug in tester has no way to do that.

 

[iwire]

There are no "shorts" involved in the testing, and no background load on the circuit is needed (as would be the case for an AFCI.)

All the plug in tester does is take some current (~10ma) from the hot and run it through a resistor to the EGC. That creates an imbalance in the current through the sensing coil since it is not returning through the neutral.

All you did was make what user 100 said more complicated.


I agree with user 100, the quick answer is the plug in GFCI tester shorts the hot to ground.

 

[GoldDigger]

All you did was make what user 100 said more complicated.


I agree with user 100, the quick answer is the plug in GFCI tester shorts the hot to ground.

If it "shorted" the hot to ground it would trip OCPD too. The test current is strictly limited.
I know that you could call it a high resistance short or a current limited short, but I can't get away from the connotation of an unlimited current in a short circuit. A "short" of 6ma just sounds wrong to me. That is a load, not a short.
JMO.

 

[user 100]

If it "shorted" the hot to ground it would trip OCPD too. The test current is strictly limited.
I know that you could call it a high resistance short or a current limited short, but I can't get away from the connotation of an unlimited current in a short circuit. A "short" of 6ma just sounds wrong to me. That is a load, not a short.
JMO.

Remember, I said this:

....... (maybe another member will chime in with the longer, better explanation /description).

Which you did (and gave an excellent answer btw) . I wasn't sure of prayerpartners level of expertise, and only wanted to give a basic answer. And I did point out that this "short" would be interpreted by the device as a ground fault, and that the device would open as a result.

I do agree that a true short ckt involves high levels of fault current and am of the school of thought that it is limited to contact between ckt conductors (which an egc is not)....... But bear in mind we are talking about testing the components of a receptacle here and I prefer to avoid a Catsup vs. Ketchup type of confusion.

 

[GoldDigger]

... and I prefer to avoid a Catsup vs. Ketchup type of confusion.

Do you know the fundamental difference between Ketchup and Catsup?


Ketchup is made with tomaytoes.
Catsup is made with tomahtoes.

 

[kwired]

Remember, I said this:



Which you did (and gave an excellent answer btw) . I wasn't sure of prayerpartners level of expertise, and only wanted to give a basic answer. And I did point out that this "short" would be interpreted by the device as a ground fault, and that the device would open as a result.

I do agree that a true short ckt involves high levels of fault current and am of the school of thought that it is limited to contact between ckt conductors (which an egc is not)....... But bear in mind we are talking about testing the components of a receptacle here and I prefer to avoid a Catsup vs. Ketchup type of confusion.

So he should have used "low impedance ground fault" in his description then, which the breaker would also respond to, but a GFCI is supposed to respond to both high and low impedance ground faults, as long as the amount of fault current exceeds the 4-6 mA range that is the standard trip setting.