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#50208 - 03/26/05 06:44 PM gfi receptacle vs gfi breaker  
frank  Offline
Member
Joined: May 2001
Posts: 376
windsor ontario canada
Is there any functional difference between a gfci receptacle and a gfci breaker.I know gfci receptacles are calibrated to trip at 5ma?thanks


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#50209 - 03/26/05 06:56 PM Re: gfi receptacle vs gfi breaker  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Both have approx. 5ma trip levels


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#50210 - 03/26/05 09:47 PM Re: gfi receptacle vs gfi breaker  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
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....


#50211 - 03/26/05 11:24 PM Re: gfi receptacle vs gfi breaker  
bucketman  Offline
Member
Joined: Oct 2004
Posts: 72
vancouver WA, USA.
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?


#50212 - 03/27/05 12:54 PM Re: gfi receptacle vs gfi breaker  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
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).]


#50213 - 03/27/05 01:07 PM Re: gfi receptacle vs gfi breaker  
Dnkldorf  Offline
Member
Joined: Dec 2004
Posts: 1,064
nowhere usa
Tx, NJwirenut.

Never really fully understood leakeage current like that before.

Good explaination.....


Dnk.....


#50214 - 03/27/05 03:14 PM Re: gfi receptacle vs gfi breaker  
bucketman  Offline
Member
Joined: Oct 2004
Posts: 72
vancouver WA, USA.
Vary good, thank you. [Linked Image] I feel lerned now.



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