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GFCI Protection at Panel


randynavarro
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Old house (1959). Two wire circuits - no ground wire. Open-grounded outlets.

Installing GFCI receptacles at each outlet location is considered a wise 'safety upgrade' however this homeowner installed GFCI breakers for each of the circuits.

My three-light tester did not trip any of the breakers as I went through the home.

Are GFCI breakers an adequate 'fix'?

I understand the three-light tester isn't the ideal testing device, however what would be the reason it wasn't tripping the breaker?

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Scott: Understood - GFCI's are not a substitute for grounding. Regarding the 'fix' - another way to ask is if the breakers will provide the same protection as if there were GFCI's at each outlet location?. There were other weird things on the panel anyway so I called for an electrician - be interesting to hear what he would have to say.

Kurt and Mike: I guess that is really the main question - how does a GFCI on an ungrounded circuit actually protect a person in a real life circumstance? Is a lamp cord getting cut considered a 'ground fault'? Is a ground fault created when a child sticks a key into the receptacle?

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The GFCI is comparing what's coming through the hot side of the circuit versus what's returning on the neutral side. If there is a variance outside of what the device allows, it cuts power to the circuit faster than one's nervous system can react. If you don't have a ground, but you inadvertently create a ground - say like with a ratty old 40-year old toaster with a frayed cord and a metal housing, by touching the housing and the faucet at the sink at the same time, your body becomes the easier path for that current to return to ground and it shunts into you. The GFCI senses that something has changed on the neutral leg of the circuit and cuts that power faster than my wife on the way to a Bon Marche sale, in plenty of time for your heart not to go into defrib or whatever it's called.

Cutting a cord will probably cause a short and trip the breaker, the kid sticking the keys in the receptacle might do the same thing, or cause a ground fault, either way, the GFCI will sense the change and trip if that variance is outside of the GFCI's tolerance range.

Okay, that's my understanding of it and I'm not real comfortable with electrics, so you electro gurus can have at me and tear my explanation to shreds. [:-blindfo

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Originally posted by randynavarro

Scott: Understood - GFCI's are not a substitute for grounding. Regarding the 'fix' - another way to ask is if the breakers will provide the same protection as if there were GFCI's at each outlet location?.

Providing that the GFCI breakers are working properly then yes, absolutely, the outlets will enjoy the same protection.

There were other weird things on the panel anyway so I called for an electrician - be interesting to hear what he would have to say.

Kurt and Mike: I guess that is really the main question - how does a GFCI on an ungrounded circuit actually protect a person in a real life circumstance?

GFCI protection has nothing whatever to do with whether or not the circuit is grounded. It will work in exactly the same way on a grounded or ungrounded circuit. Mike's explanation of its operation is exactly correct.

Is a lamp cord getting cut considered a 'ground fault'?

If you cut a lamp cord with scissors that have insulated handles you're going to create a short circuit between the two wires in the cord. This is not a ground fault. The circuit breaker in the panel might trip (unless it's an FPE) but the GFCI shouldn't trip.

If you cut a lamp cord with uninsulated metal scissors, some of the current will travel through your hand, through your body and through the ground. This is a ground fault and the GFCI should trip in response to it.

Is a ground fault created when a child sticks a key into the receptacle?

Probably. The key goes into the receptacle. The current flows through the key, through the child's hand, through the child's butt and through the ground. This is a ground fault.

If the child has two keys and sticks them into either side of the receptacle (and he's insulated from the ground), he'll be killed. There'll be no ground fault and the breaker won't trip till he's already received a deadly shock.

- Jim Katen, Oregon

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Originally posted by randynavarro

Old house (1959). Two wire circuits - no ground wire. Open-grounded outlets.

Installing GFCI receptacles at each outlet location is considered a wise 'safety upgrade'

Nope. I've gotta disagree. It's not an "upgrade" it's a requirement of the NEC. That is, when you replace a two-slot receptacle you must do one of three things:

* Replace it with another two-slot receptacle.

* Replace it with a three-slot receptacle and ground it properly.

* Or replace it with a three-slot receptacle and provide ground fault interrupter protection.

You can find all this and more in section 406.3(D)(3).

however this homeowner installed GFCI breakers for each of the circuits.

That's ok but the receptacles are supposed to be labeled "GFCI Protected, No Equipment Ground." No one seems to actually do this.

My three-light tester did not trip any of the breakers as I went through the home.

The three-light tester attempts to create a ground fault by shunting a small amount of power to ground. Since there's no ground in the receptacles, it didn't work. The test button on the GFCI breaker would have told you if the GFCI feature was working properly. It doesn’t shunt to ground, it uses a resistor to create an imbalance in the circuit so it’ll work even without a ground.

- Jim Katen, Oregon

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