Theory

[JWinters]

Today I had alittle chat with a fellow worker about GFCI's tripping. I asked him would the GFCI trip if you had the black wire in one hand and white in the other off the load . Or same off a GFCI breaker. I assumed that it would trip from change in amps threw the body. But he said it would not trip because same goes in one arm same comes out other arm . Any thoughts would help.

 

[480sparky]

If you grabbed the hot (ungrounded) and white (grounded) of a GFCI protected circuit, it would not trip. The circuitry would simply 'see' you as a load.

Only if 5mA or more left you through some other path (ground fault somewhere) would it trip.

 

[JWinters]

Thanks for your response.

 

[Jim W in Tampa]

Would depend on if your insulated enough from the floor. If you are and you touch both wires you will not feel to good and might not live to tell us about it. If all you touch is the hot and your insulted nothing will happen.

 

[growler]

I have never really considered that situation. In theory I think he is right. If you were the load and no current leaking to ground there wouldn't be any reason for a GFCI to trip. One source of resistance is the same as another when it comes to current flow so I guess we are just big carbon resistors.

I can't think of that many situations where you would be totally insulated from ground and holding the return ( neutral ) in one hand and the hot in the other.

Maybe someone can come up with a reason for it to trip, sure would make me feel better.

 

[glene77is]

I can't think of that many situations where you would be totally insulated from ground

24 KOhms is the key to the passage of 5 mAmps to ground.
120 Volts through 24 KOhms is 5 milli Amps.
Good rubber soled shoes may provide this, unless wet.

 

[Jim W in Tampa]

I have never really considered that situation. In theory I think he is right. If you were the load and no current leaking to ground there wouldn't be any reason for a GFCI to trip. One source of resistance is the same as another when it comes to current flow so I guess we are just big carbon resistors.

I can't think of that many situations where you would be totally insulated from ground and holding the return ( neutral ) in one hand and the hot in the other.

Maybe someone can come up with a reason for it to trip, sure would make me feel better.

You likely would need to take some serious effort to get yourself that well insulated

 

[growler]

Today I had alittle chat with a fellow worker about GFCI's tripping. I asked him would the GFCI trip if you had the black wire in one hand and white in the other off the load . Or same off a GFCI breaker. I assumed that it would trip.

Thinking about this some more. That's not really the intended use of GFCI protection in the first place. You would have to be working on a live circuit to get your paws on the hot and neutral at the same time.

GFCI protection is used to protect a person useing equipment that may become energized and short to ground through the body of a person. That's what it was designed for and that's what it does.

The way to be protected from having a hot in one hand and a neutral in the other is to turn power off when working on the circuit.

 

[steve66]

Thinking about this some more. That's not really the intended use of GFCI protection in the first place. You would have to be working on a live circuit to get your paws on the hot and neutral at the same time.

GFCI protection is used to protect a person useing equipment that may become energized and short to ground through the body of a person. That's what it was designed for and that's what it does.

The way to be protected from having a hot in one hand and a neutral in the other is to turn power off when working on the circuit.

Very true.

I think almost any pair of work shoes is going to provide at least 24K of resistance. So in a real situation, I think it is very probable the GFCI will NOT trip.

The only likely way I see the GFCI tripping is if someone is standing ankle deep in water, or if they are barefoot on a concrete floor, or if they have their arm or something leaning against a grounded surface.

 

[RICK NAPIER]

I am curious if anyone is willing to try this out.

 

[480sparky]

I am curious if anyone is willing to try this out.

Needless and completely unsafe. It will not trip. GFCIs cannot tell the difference between an actual load of 24kohm and a human body with a resistance of 24kohm.

 

[roger]

Simply stated, if the current adds to zero between the ungrounded and grounded conductors, the GFCI will not trip and parts of your body may begin to smoke after a period of time.

Enter a third current path of more than 5-6 mA and a properly working GFCI will trip.

Roger

 

[zog]

Actually the ground has nothing to do with the GFCI operating. GFCI's operate with a small current transformer that surrounds both the live and neutral wires. The secondary winding is connected to a sensitive electronic detector, which can trigger a circuit breaker or contactor in series with the 120-volt line. Under normal conditions, the line current in the line conductor is exactly equal to the current in the neutral, and so the net current flowing through the current transformer is zero. Consequently, no flux is produced in the core, the induced voltage is zero, and the circuit breaker remains closed.

Suppose now that current IF leaks directly from the live wire to ground. This could happen if someone touched a live terminal. A fault current would also be produced if the insulation broke down between a motor and its grounded enclosure. Under any of these conditions, the net current flowing through the CT is no longer zero, but equal to IF. A flux is set up and a voltage is induced which trips the CB.