Gfci

[dmack]

This may be dumb question but here goes. I am testing a GFCI receptable (first) and it trips manually. The three light thing says everyting is wired correctly. I push the trip button and the GFCI does not trip. I test two receptables down stream with three light thing. Everything is wired correctly? I test the trip botton and the (first) receptable trips. Why does the GFCI trip when plugged into a receptable down stream but not when it's plugged into the actual receptable?

[Paul W. Abernathy]

David,

Firstly, a question is NEVER dumb if you really do not know the answer. A dumb question is one that is NOT asked at all.

Secondly, the intent of the manufacturer is to test the GFCI from the switch located on the actual device. Many people mistake the fact that external testers can have errors....This is widly known.

While they do work most of the time...problems can occur.

With that said, their is a chance the GFCI is defective in that the units protection is working on the load side of the device but in all cases the plugs on the unit itself are line side attached and always protected. ( if wired correctly that is...)

Now if the unit trips...and resets with no problem and you are able to test the units down stream and they work....and the reset works on the actual GFCI itself based on the manufacturers information they are going to attest that the GFCI device is working per their specs.

Now..do not get me wrong......it could be a bad GFCI..I am just telling you the standards the manufactuere recommends.

Now in many cases the GFCI is wired up wrong but in that case in the new units the light on the GFCI will not come on or turns a different color from the correct color as listed in the instructions....and will not trip when you press the test button.

Now this may sound like bad advice...but I have (2) testers with me on all jobs..sure I have the more expensive version from Surtest..but I also have a cheaper version and I check GFCI's ( Electrician or NOT ) with both....as well as the TEST button on the unit.

[Bruce A. King]

based on the info, the GFCI is probably wired backwards or defective.
The input and load are likely reversed. The 3-light tester will not show that.

[Paul W. Abernathy]

I would lean towards.... trying another tester. If wired backwards the downsteam would not trip the GFCI and again if a newer GFCI it would not work either on the test switch.

The good thing about a Suretest style testing..obviously which is why it costs more is it can also test for missing EGC or Bootleg grounds.

Does not solve the issue of the unit working down stream, which would lead me to want to ask the age of the GFCI in question ( not in the 1980's I hope ) and what model it is.

[Paul W. Abernathy]

the GFCI didn't trip by the trip button on the unit or can not be reset after triping the unit it either has the feed conductors connected to the load terminals which can only happen on older GFCI's (Non-fail safe) or on newer ones which has had the reset button reset then the feed wires switched to the load side. Or flat out you got a bad lot of GFCI's.

If you look at the two diagrams of a GFCI circuit below, you can see how the test button places a 5ma load from the load side hot to the line side neutral which will act just like a ground fault. If these GFCI's are used to replace receptacles on a non-gounded circuit they will still funtion but a plug in tester will not be able to test them as they require a grounding source to "leak" the current to, to cause the imbalance to trip it.



This diagram shows the fault current which trips the GFCI.


Your plug-in GFCI tester requires an equipment grounding conductor to function and without one, it will not trip the external unit. The interal test puts a load from the hot on load side of the current sensor to the neutral on the line side of the sensor creating an imbalance of current through the sensor. This is a true test. The GFCI does not require the EGC to function. If there is any leakage above the 4 to 6 mA trip point the GFCI will open the circuit.

How OLD is this house and GFCI you are testing...any idea?

[dmack]

Thanks for the responses. The home owner is my brother in law. I will relay this information to him.

[Paul W. Abernathy]

David,

If he has any questions he is always free to call me. Anyone here is free to do that if they are on a site and have a question in regards to electrical issues...Just dont call me after 7:00Pm EST....thehehe.

[Jay Moge]

Originally Posted by bking

based on the info, the GFCI is probably wired backwards or defective.
The input and load are likely reversed. The 3-light tester will not show that.

every time i wire a GFCI wrong (load and line reversed) A.) alway to show the other guy what not to do and B.) it won't reset. just trips right away all the time. when i fix it, all is good.

[JayKline]

Paul - thanks for the illustrations. I use a Suretest and I carry around a 3-bulb tester for back-up. But from your post, it appears that it is important to use the integral test button on the GFCI receptacles to test the trip feature. Isn't that what the manufacturer's recommend anyway ? After reading your post, I think I'm beginning to understand why they recommend that.

[Paul W. Abernathy]

Yes, The internal test feature on the GFCI is the best way because it does actually test the mechanical sequence of the Hot to Neutral test...versus the external units needing a EGC to be able to accuratly do the test.

As someone else also mentioned it is important to note that on GFCI's that are installed correctly ( not from the 1980' mind you ) that if you wire them wrong they just will not work correctly....

The advantage of a SureTest over the cheapies in my opinion is one it is a COOL TOOL and the HI's look very good when using it...it also gives you great information about the circuit itself...bootleg grounds and so on which can fool some lower cost testers...

Now again.....I do use them both...but I also do carry around BOTH at the same job site and the one I really trust honestly is the SureTest..but it also will not work correctly if the ground is not present...but atleast it tells you that before you try to test it...lol.....