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gfci question

1357 Views 6 Replies 4 Participants Last post by  curiousB
I was testing a portable gfci cord and found that it would shut off with the test button and reset normally with the reset button. Next I tested it with my gfci outlet tester and it would not shut off. Is the gfci good or bad???

Reading on line it appears that separate outlet testers will not work on a two wire ungrounded system. This is a three wire (grd-blk-wht) set up. The gfci has a 10mA trip current. It appears that most Gfci's are in the 4-6 mA range.

Could it be that the outlet tester is a lower current trip rating than the 10mA and that is why it will not trip the gfci???

bottom line is the pigtail gfci any good?

thanks for any input and thoughts.

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Outboard testers operate by sending some current down the ground wire. If the ground isn't connected then such a tester won't work. This doesn't mean the GFCI is faulty, its just the outboard tester can't create a leakage (fault) current without a ground. So it isn't anything to do with how much of a leakage current the outboard simulator makes vs. the internal GFCI test button. Without a ground return the outboard tester leakage is zero mA.

The test button on the GFCI device works differently, it sends a return current back down the neutral but it sends that current return outside of the differential transformer inside the GFCI. This creates a current imbalance which trips the GFCI. This is why the GFCIs test switch can work without a ground line.
According to the specs of every GFI outlet I've installed, the only way to test them is with the "Test" button on the device. I will bet that your GFI cord is the same. If you press the Test button and it trips, you can assume it is working.
Thanks guys. Yesterday I spoke with an electrician (co-worker) about gfci testing. He suggested that the older gfci's may and do fail to operate correctly even if the test button works. The newer ones don't fail with age. Older styles have to be exersized monthly or the contacts weld together.

Also different testers do have different mA leakage which is why some gfci;s will not trip on an external test.

His advise, throw it away, better safe than sorry.

On a totally different note: K_buz, you mentioned on another thread about cordless vs corded drills and using extention cords "that they come in different lengths" I am being polite by posting this here. You missed the obvious, "they also come in different colors" HA, HA

Your electrician friend is wrong. This is nothing to do with GFCI sensitivity. I outlined the exact issue two posts prior.
GFCI devices do not use a ground wire in the test or fault mode. GFCI devices will/should work fine without a ground present.
GFCI devices do not use a ground wire in the test or fault mode. GFCI devices will/should work fine without a ground present.
Of course. I outlined this above. An external GFCI tester will not work without a ground.


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