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Joined: May 2001
Posts: 376
frank Offline OP
Is there any functional difference between a gfci receptacle and a gfci breaker.I know gfci receptacles are calibrated to trip at 5ma?thanks

Joined: Jan 2003
Posts: 4,391
Both have approx. 5ma trip levels

Bob Badger
Construction & Maintenance Electrician
Joined: Sep 2001
Posts: 806
In my experience, GFCI breakers exhibit more of a tendency toward nuisance tripping than the receptacle types, particularly when feeding a very long branch circuit run, or just about any length of old cable. I presume this has to do with leakage to ground (either resistive or capacitive) in the cable run.

Putting the GFCI at the point of use avoids tripping from these leakage currents. The receptacles are also generally less expensive than the breakers....

Joined: Oct 2004
Posts: 72
So how do you get

"(either resistive or capacitive) in the cable run."

I could see voltage drop but I don't know how you get reactence in just a cable run?

Joined: Sep 2001
Posts: 806
You have capacitance between any 2 insulated conductors in a raceway or cable, as well as between the conductors and ground. A capacitor is simply 2 conductors (the copper wires or metal raceway/armor) separated by an insulating dielectric (the wire insulation). The potential leakage gets higher with a longer cable run (adds more capacitance) or older, degraded insulation (lowers leakage resistance).

If the resistance gets low enough or the capacitance gets high enough, sufficient leakage current can be present to trip the GFCI, or to lower the "overhead", so additional leakage below the usual 5 mA will be enough to cause a trip.

[This message has been edited by NJwirenut (edited 03-27-2005).]

Joined: Dec 2004
Posts: 1,064
Tx, NJwirenut.

Never really fully understood leakeage current like that before.

Good explaination.....


Joined: Oct 2004
Posts: 72
Vary good, thank you. [Linked Image] I feel lerned now.

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