Hoping this is my last question on this topic - ref. Following-up from New Circuit Help Please - Feeding 2-gang receptacle boxes with MC 12/4

You kind souls saved me from myself. I’ll implement the “MWBC recovery plan” you recommended to overcome my screw-up — for having purchased 12/4 with a blue wire instead of a gray wire ... I thought I was going to be able to tape the blue wire with white or gray tape but learned via the aforementioned thread that you can’t tape over wire smaller than 4 GA (ref. NEC 200.6(A). Many thanks to ECnerwal, ThreePhaseEel, and Harper - Reinstate Monica for having my back! Thank you!

So, here’s the updated plan, annotated as a recovery plan so folks who find this some time in the future realize this was not the ideal solution. Don’t do it this way! Don’t be like me. Read the other threads first! This could have worked if I had bought the MC 12-4 with a gray wire. But I didn’t.

You’ll note that I clarified I’m coming from a sub-panel, and I’ll feed from a section of 12/3 romex (from behind the wall in an unfinished storage room).

MWBC Implementation to Salvage the 12/4 with a Blue Wire Updated

Hopefully this third time is a charm. Sharing the neutral on this MWBC works because the 2-pole breaker feeds two hots 180 degrees out of phase with eachother, so even when pulling 20A from each of the hot legs (red and black), the shared neutral is pulling 20A while pushing 20A, so the net is 0A on the neutral. The max current on the neutral happens when only one circuit is pulling 20A. Looking for confirmation this is all good before I sign off and finish this installation so I can start making sawdust instead of smaller and smaller pieces of wire.

Adding this pic given @bigchief response below: GFCI’s I’m using - have side- and back-wire connections Assuming this means I can use one back- input for line and the second back- for continuing to the load, without using a wire nut.

Thank you all very much!

Sincerely, Rich 🎄🎄 Happy Holidays 🎄🎄


Looks good to me. The most important advice I think I can mention is to make sure the two pole breaker you buy for this circuit is listed for use in your panel. Many breakers fit or seem to fit), but the bus connector is slightly different and doesn't connect well resulting in connection problems and damage to the panel. If you are not sure, send a picture of the panel and we can tell you what breaker to get.

If you haven't purchased the outlets yet, you might see if a GFCi breaker and 4 regular outlets is cheaper than the 4 GFCI outlets. You also need to consider where you would prefer the GFCI reset switch to be, at the panel or each outlet.

You must pigtail neutrals on multi-wire circuits but you don't have to pigtail the hots at each box, make sure you don't use the load connectors anywhere in this plan, but if the line screw terminals are screw-and-clamp rated for two conductors you can attach both red and both black wires directly to the GFCIs if you desire to avoid extra pigtails.

  • Thank you so much, bigchief. I have purchased Eaton CH-type breakers to go with my Eaton CH panel, and I already have a few extra 120/240V 2-Pole breakers for my panel. I have 6 GFCI outlets for a different string that I planned to run, so just need to buy a few more. I’ll keep the resets at each GFCI outlet. I’m not understanding your last paragraph, “if the ... you can attach both red and black wires directly to the GFCI if you desire to avoid extra pigtails.” I’ll post a pic of the GFCI in a minute—it’s made for side- and back-wire. – riffin-rich Dec 20 '20 at 16:43
  • I think @ThreePhaseEel’s minor edits clarified my question. I posted a pic of my GCFI at the bottom of my first post above. – riffin-rich Dec 20 '20 at 16:49
  • 2
    Don't use the load terminals on the GFCI under the yellow sticker. But you can put both red wires on the line screw since it is rated for two conductors. Or you can always pigtail like you show in your plan. – bigchief Dec 20 '20 at 16:55
  • Original pic updated for future readers. Thanks again, gentlemen. – riffin-rich Dec 20 '20 at 17:01

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