Multiwire branch circuit tripping GFCI's

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iwirehouses said:
I guess the top circuit is the only one with problems. The bottom circuits seem to be running fine.

The 4" sq. box on the left (two "standard" duplex receptacles) is fed from the load on the gfi in the center box.

All my connections are extremley tight. You'd ned some linemen pliers and little time to get any connections apart. The only thing thats been brought up is the fact the I didn't wrap tape around the gfi's. There is a bare ground wire in each box and they are standard 4"sq boxes with raised metal covers. Its a good possibility a ground could be touching a neutral. I know this raises hell with arc fault breakers, but have never personally seen this cause a problem on a gfi.

When all is said and done, is my wiring correct? or should I run a seperate 12/2 to the middle box on the top circuit and abandon the 12/3 multiwire branch circuit idea?
Click to expand...

Dedicate the red line to the top three receps. and the black line to the bottom 2. It appears to me that you are sharing a neutral downstream of a GFI. Should work.
 
iwirehouses said:
Would a ground touching a neutral cause this on a gfi? I never thought so.
Click to expand...

It only takes a few mA of current somehow 'bypassing' the GFCI to cause it to trip. If the neutral on the load side of the GFCI touches ground (or another circuits neutral) then enough current can flow through this parallel path to trip the GFCI.

I have also seen references to some GFCIs that detect this condition and trip even if nothing is plugged in.

-Jon
 
Ok, cool. Well then it sounds like thats probably my problem. One last question....If I disconnect the ground and neutral at the panel and ohm it out, it should read zero, right? Or is it possible for it to have some kind of value and still be fine?
 
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