I was using a wet saw in the garage yesterday. It was pluggged into a GFCI-protected outlet that is on an older (knob-and-tube) 2-wire circuit (no true ground). Once my shoes and socks got wet, if I touched the frame of the saw, I’d get a definite shock, but clearly not the full 110. I thought ANY leak to ground would trip a GFCI, but this one tests (via the button) fine. What’s going on?
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You said "protected" and not GFCI receptacle.
If this is a "downstream "receptacle then it might not actually be downstream of the GFCI.
The other possibility is that the leakage is less than the 5 ma needed to trip, but enough to sense the voltage.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Sorry for the confusion- I was plugged into the outlet itself.
"I was plugged into the outlet itself."
Well, there's your problem. NEVER plug yourself directly into an outlet!
(Sorry, I couldn't resist.) ; - )
Mike HennessyPittsburgh, PA
If you don't have a ground, you are not protected. The GFCI is acting like a regular plain receptacle.
Bear
Edited 3/27/2007 4:00 pm ET by bearmon
Really? Then why is it accepted in the code? The inspector passed it- it's labelled "No equipment ground", and I thought a GFCI on an ungrounded ckt. was the way to increase the safety in wet areas.Bill
me too.
Bullfeathers!!!I'm guessing that the OP was getting a tingle below the 5ma cutoff.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Must be- I'd say the 'tingle' is about like when you lick a 9v battery (don't ask me how I know!)Bill
"If you don't have a ground, you are not protected. The GFCI is acting like a regular plain receptacle."Wrong.A GFCI works by measuring the difference between the current in the hot leg and that in the neutral leg. If they differ by 5 ma or more then it trips.The only way that the ground is even connected to the GFCI is for the grounding pin socket part of the receptacle. It has nothing to do with the GFCI funcitoning.In fact the NEC SPECIFICALLY ALLOWS THE THE INSTALLATION OF GFCI'S AS WAY OF UPGRADING UPGROUNDED CIRCUITS TO ALLOW THE USE OF GROUNDING STYLE RECEPTACLES, BUT WITH ANY GROUND WIRE..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I stand corrected. Sorry for the mis-information.Bear
GFCI could be bad, does it test when you push the button?
"GFCI could be bad, does it test when you push the button?"IIRC, GFCI will function properly on a two-wire ungrounded circuit, but the test button will not work, because that uses the ground terminal to leak a little current, thus causing the aforementioned 4-6ma difference between hot and white wires that makes the GFCI circuitry trip. Same thing with those little three-prong GFCI circuit testers, they need a ground to work.BruceT
"IIRC, GFCI will function properly on a two-wire ungrounded circuit, but the test button will not work, because that uses the ground terminal to leak a little current, thus causing the aforementioned 4-6ma difference between hot and white wires that makes the GFCI circuitry trip. Same thing with those little three-prong GFCI circuit testers, they need a ground to work."I AM GOING TO HAVE TO MAKE A RUBBER STAMP TO STAMP ON MY MONITOR ABOUT THIS.WRONG!!!!!!!!!!!!!!!!!!!!!!!!!The internal GFCI test button does not need a ground. It connects a resistor from the load side (after the sense coil) on the hot to the neutral side before the sense coil.So it exactly similars a current imbalance..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"I AM GOING TO HAVE TO MAKE A RUBBER STAMP TO STAMP ON MY MONITOR ABOUT THIS.WRONG!!!!!!!!!!!!!!!!!!!!!!!!!"Gonna stamp that rubber stamp right next to the little dots of "Whiteout" from correcting text errors?Thanks for the explanation. Presumably the three-prong testers use a resister also? Useful to determine if an ordinary receptacle in a bathroom or kitchen is protected by a GFCI somewhere upstream.BruceT
The 3 prong testers work similarly, but they require a grounded circuit.The only real way to test a downstream receptacle is to see if it works and then use the GFCI test button and the see that the downstream receptacle is dead..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
A ground ... good or otherwise... is NOT necessary in order for a GFI to operate. Indeed, a GFI will work fine without any ground at all.
That said, the GFI is set to trip anywhere from 4-6 milliamps of leakage. This level is, under ordinary circumstances, felt by most folks as a mild shock. A tingle, if you will.
Give yourself a better connection, and that shock will feel much worse. Let the shock pass through different parts of your body, and it will feel much different, as well.
Even so, I would not rule out that the GFI is failing to operate. If you can test it, please do so - both with the test button, and a plug-in tester. GFI's do wear out, and they can be wired incorrectly.
The plug in testers don't work without a ground.UL listings, manufactures instructions, CPS, etc only accept testing with the bultin test botton.Unless some other selftest this is a very good selftest. It puts a resistor in the circuit from Hot after the GFCI to neutral before. And baring a larrge change in the reistor, which would be unusal, it is a very realistic test..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I don't have a tester, but the button does work. I suppose I could connect a bare wire to the hot side of the receptacle, grab it one hand, and grab a cold water pipe in the other- I'll let you know how that works.; )Bill
And if we don't hear from you -- well, it was in the name of science.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=67781.1&search=yhttp://forums.taunton.com/n/mb/at.asp?webtag=tp-breaktime&guid=488F6150-67D2-4C83-9FF0-433B4D4E391E&frames=nohttp://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=77731.1&maxT=15"Spent about 10 hours last week with my feet in buckets of 14% salt water turning the dial on a variac doing experiments on myself untill my feet were shaking, but that is only a cross section of 1 person. DW agreed to some tests also, she is at the far end of sensitivity from me, she quit at about 2 mA, whereas 20 mA was about my pain limit.".
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.