House built in 1952, 100A Service, Ungrounded, GFCI Breaker on Branch Circuit

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fraymond

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Huntsville, Alabama
I was going to put GFCI receptacles in all locations. GFCI's too big for the box so I decided to use a SQ D QO series GFCI (no arc flash). Only one 100W lamp plugged in. When lamp is turned off breaker remains reset. Turned lamp on, breaker trips, Turned lamp off breaker will reset. Checked resistance at breaker, 45ohms. Turned lamp off... open circuit i.e. infinity. Moved GFCI breaker to different branch... same results!?!? Put original standard breaker back in... no problem. House had an addition added. 100A service in garage with another breaker panel added in hallway. I looked in the garage panel and saw a piece of romex that was added going to a GFCI breaker (blue plastic box). I suspect the GFCI is grounded. Was going to disconnect tomorrow to see if this would make a difference. Any thoughts please...
 
fraymond said:
I was going to put GFCI receptacles in all locations. GFCI's too big for the box so I decided to use a SQ D QO series GFCI (no arc flash). Only one 100W lamp plugged in. When lamp is turned off breaker remains reset. Turned lamp on, breaker trips, Turned lamp off breaker will reset. Checked resistance at breaker, 45ohms. Turned lamp off... open circuit i.e. infinity. Moved GFCI breaker to different branch... same results!?!? Put original standard breaker back in... no problem. House had an addition added. 100A service in garage with another breaker panel added in hallway. I looked in the garage panel and saw a piece of romex that was added going to a GFCI breaker (blue plastic box). I suspect the GFCI is grounded. Was going to disconnect tomorrow to see if this would make a difference. Any thoughts please...
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Possible high resistance ground fault resulting in only just greater than 5ma of ground fault current to trip the GFCI?

Try with a different lamp with the same bulb and watch the results.
 
I suggest measuring the resistance from the neutral wire of the circuit in question over to the neutral bar and verify that it shows an open circuit (with both the hot and neutral wires removed from the GFCI breaker). This is to make sure that this neutral wire is isolated from any other circuits.

So these are 2-wire circuits without a ground?
 
synchro said:
I suggest measuring the resistance from the neutral wire of the circuit in question over to the neutral bar and verify that it shows an open circuit (with both the hot and neutral wires removed from the GFCI breaker). This is to make sure that this neutral wire is isolated from any other circuits.

So these are 2-wire circuits without a ground?
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Yes sireebob
 
hbiss said:
Did you remove the neutral for that circuit from the neutral bar and connect it to the GFCI breaker's white pigtail?

-Hal
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No I didn't Hal! I have the pigtail going directly to the neutral busbar. How is the neutral wire normally connected to the pigtail i.e. wire nuts, butt splices, etc... This sounds plausible! Now that I think about it a GFCI receptacle has it's neutral isolated on the bottom half of the receptacle.
 
fraymond said:
No I didn't Hal! I have the pigtail going directly to the neutral busbar. How is the neutral wire normally connected to the pigtail i.e. wire nuts, butt splices, etc... This sounds plausible! Now that I think about it a GFCI receptacle has it's neutral isolated on the bottom half of the receptacle.
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But... How are the electronics of the breaker powered if it does not have a reference such as the neutral bus which happens to be earth grounded in this case???
 
ptonsparky said:
I had an inspector tell me once that he would rather see the bootleg ground then nothing. :oops:
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Wow, that's just scary, especially since code has provisions for GFCI protecting a two wire system as long as it has the sticker on it. When I've run across old two-wire systems that had unpermitted updates it's either GFCI or back to two-prong receptacle. I am frequently shocked (no pun intended) at some of the things I hear about inspectors from neighboring AHJ's...
 
fraymond said:
OOHHH... Now it makes since!!! Excellent! Thank you all for responding!

Please be more specific in regards to shared neutrals. Can they be detected?
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Shared neutral is typical with MWBC. Two hots and a neutral. Residential. This was a very common practice.
Some installers would tie all the neutrals together in a j box and not concern themselves with how they are paired up.
Yes, they can be detected. Generally with a continuity test.
Turn off all the breakers. Remove all the neutrals from the neutral bar.
Check each hot for continuity to each neutral. A neutral with continuity to more than one hot means it’s shared. You may need to cycle light switches etc.
 
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