I’m in the process of wiring my shop. I had a subpanel installed and I’m now running circuits. My question is this- I want to have a slew of 2-gang boxes around the place, with each side of the box on separate circuits. I have two separate GCFI outlets in the first box, and the rest of the boxes come off that one.
The problem is that I can’t get both circuits to stay live at the same time. If I push the reset on one of the circuits, the other one cuts out immediately. A friend suggested running 12/3 through the boxes and sharing the neutral across both circuits, and since he’s a home inspector, I did what he suggested. Is the common neutral the source of this problem? Or do I need to look for a different problem?
Thanks.
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Replies
"Is the common neutral the source of this problem? "
Absolutely.
Once you start connecting on the LOAD side of a GFCI you need to keep the neutrals separate.
You have 3 options here.
Replace the breakers with a 2 pole 120/240 GFCI breaker ($$$$) and the use regular recptacles at all locations.
At the first box where you have the two GFCI receptacles replace the 12/3 that feeds the downstream receptacles with 12/4 (2+2 not 3+1) or run two separate 12/2's. I wanted to mention the 12/4, but it is probably hard to find.
Install GFCI receptacles in each box ($$$ depending on how many locations).
The GFCI has a sensor that compares the current hot the hot terminal against that on the neutral. If they differ by 5 ma it trips. Thus the neutral on any down stream load has to be connected to the neutral on the GFCI load terminal and ONLY to that load terminal. If it connects any place else either the return current can be shunted off or you can get return current from a source other than that GFCI hot terminal.
And just a note, for any multi-wire circuit make sure that the 2 breakers are on different legs, a 2 pole breaker is needed if any one device has both hots on it (which is not the case in your project), and the neutral (while still a mutiwire circuit) can not run through a device, but needs to be pigtailed.
Any shared neutral beyond a GFCI should always trip it. It's design is to monitor power differences between the hot and neutral.