Will a GFCI work correctly without a grounded wire?

sweetbabyjames5July 29, 2011

Electrical is something I don't pretend to know anything about. So, I'm here asking this question because DH and I had two electricians tell us different things regarding GFCIs. We just bought a "new" old house. Electric needs to be updated. One electrician said GFCIs need to be used with grounded wires, which we don't have in most of the house. The other electrician said GFCIs will still work without grounded wire. Not sure who to believe. Please help!!!

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btharmy

You first need to understand there are similar terms that need to be used properly. A "grounded wire" or grounded conductor, is commonly called the neutral. A grounding conductor is commonly called the ground. So, with that said, yes, grounded wires (neutrals) are required for GFCIs to operate. Grounding conductors are not required.

    Bookmark   July 30, 2011 at 12:36AM
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bus_driver

Not exactly. There are 240 volt GFCIs that do not involve a neutral. The only necessary conductors for proper operation of a GFCI are the circuit conductors. For 120 volts, one of those conductors is the neutral.

    Bookmark   July 30, 2011 at 8:20AM
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hendricus

To put it simply, if you just have the two wires, black and white, the GFCI will work. In fact, a GFCI is recommended in this situation because it will provide protection even though you have no equipment ground.

    Bookmark   July 30, 2011 at 8:25AM
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petey_racer

SBJ5, The second guy is not much of an electrician if he doesn't know that a GFI will absolutely work without a grounding conductor. In fact, as the first guy said, a GFI is a legal and safe 3-prong retrofit for circuits without a ground.

btharmy, while you are correct, explaining grounded and grounding conductors to a DIY that has no idea about electrical work is pointless IMO, and will only serve to confuse her.
I think we all know she means the equipment ground and not the neutral.

    Bookmark   July 30, 2011 at 9:02AM
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Billl

A GFCI measures any current difference between the live and neutral wires. If they don't match, current is going somewhere it isn't supposed to and it trips. It doesn't require a ground to do that.

    Bookmark   July 30, 2011 at 3:40PM
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civ_IV_fan

put simply, in any situation posing a threat to human safety, a gfci will trip instead of shocking you. this functionality is not affected by the presence of a ground.

first electrician wrong, second right. if you buy a gfci outlet it comes with a sticker to be specifically affixed when the gfci has no ground, so there is a way to know. so put on those stickers!

a final thought: retrofitting two wire with GFCI's plus the usage of a whole-house surge protector is a fantastic alternative to rewiring.

    Bookmark   August 1, 2011 at 11:16AM
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petey_racer

OK, first off, I was mixed up. I meant to say the first guy is wrong. Sorry 'bout that.

Second.
civ_IV_fan, a GFI will not prevent a small shock (pain). It will prevent a sever shock/electrocution (death).

    Bookmark   August 1, 2011 at 3:38PM
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brickeyee

"put simply, in any situation posing a threat to human safety, a gfci will trip instead of shocking you. this functionality is not affected by the presence of a ground."

And it may provide NO PROTECTION if you are across the hot and neutral on the load side of a GFCI.

Most of the time you have a ground connection that unbalances the hot-neutral through the GFCI, but it is possible to be isolated enough to not leak current to another path.

    Bookmark   August 2, 2011 at 10:03AM
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groundrod

the first electrician was an inspector and knows his plug in testor doesn't work without a ground wire, therefore he thinks the gfci doesn't work. silly inspector!

    Bookmark   August 2, 2011 at 9:30PM
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brickeyee

"the first electrician was an inspector and knows his plug in testor doesn't work without a ground wire, therefore he thinks the gfci doesn't work. silly inspector!"

The plug in tester is not even a reliable way to check a GFCI.

The 'TEST' button on the face IS the recognized way.

The small testers do not have adequate precision in the 'leakage' current they simulate.
They are a 'meatball' way of verifying that a regular receptacle is on the LOAD side of a GFCI.

They put a load from hot to ground to unbalance the current.
No ground, no current, but it has nothing to do with the GFCI working correctly.
They put the unbalance around the sense coil between the hot and neutral.

    Bookmark   August 3, 2011 at 9:34AM
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Ron Natalie

You can always use the method the guy I worked with used to use. Lick your thumb and then touch the non-grounded conductor. The GFCI ought to trip (unless you manage to bridge yourself across the two protected conductors).

(Admittedly this was before the days of GFCI's, it was how he detected the hot bus).

    Bookmark   August 3, 2011 at 9:39AM
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