I plan to use a tandem(AKA duplex, slimline, twin, half-height, half-inch, double or wafer breakers) circuit breaker for kitchen.

The 20 Amp Tandem Single Pole Type QT Circuit Breaker ( here is the link to it ) will feed 2 GFCI outlets for countertop.

Now, I ask if is OK this setup. Inspector says that is OK as long the breaker is on dual phases.

Here is her answer: "You can use the slimline product, but it must be on dual phases.They each need a neutral."

What does it means? I couldn't find some info about twin breakers for dual or single phase.

2 Answers 2


Lost in translation

The inspector is giving you the standard warning not to use double-stuff breakers on MWBC (shared neutral) circuits. Sounds like you fully understand that requirement... and they aren't telling you anything new

  • what do you mean by "you are way ahead of them..."?
    – cadobe
    Jun 11, 2019 at 22:15
  • I agree for tandem 2 hots 2 neutrals no way to do a MWBC with tandems.+
    – Ed Beal
    Jun 28, 2019 at 10:16

If your inspector says you need the breaker to be on two phases, that probably means you have a Multi-Wire Branch Circuit (MWBC). That means you need a proper two-slot breaker, not typical a double-stuff -- those only can grab one phase. You can use a so-called "quad" breaker, where the internal ones (and possibly the outer pair as well) are proper common-trip two pole breakers, suitable for MBWCs. See @Harper 's answer here (and the linked answers) for the full details with pictures: Why are tandem breakers on shared neutral (MWBC) problematic?

  • I do not want to use MWBC. Just keep it simple. Each circuit on its own cable.
    – cadobe
    Jun 11, 2019 at 17:45
  • Hmm I'm not sure why your inspector is insisting they be on separate phases then. I suppose your options are to either argue with your inspector or simply wire it as if it were a MWBC, with a two-pole breaker at the panel, but with separate neutral wires. Either way, if you read through the linked answer (and the ones it links to) that will give you all the info you need about dual vs single phase tandem breakers, so you can have a more informed discussion with your inspector.
    – Nate S.
    Jun 11, 2019 at 17:50
  • If she said they each need a neutral, probably wasn't talking about MWBC. If they were on a separate phase, you could use the same neutral. Very conflicting advice. If each breaker has a neutral running with it's hot, you should be fine.
    – JPhi1618
    Jun 11, 2019 at 17:56
  • @JPhi the twin breaker operate two different circuits 12-2 cable on each connection
    – cadobe
    Jun 11, 2019 at 18:04
  • 1
    As long as each cable has a white and a black, you're ok. The confusing parts come in when you want to run two circuits and you have a cable with white, black, and red. The white will be "shared" and that has to be done correctly.
    – JPhi1618
    Jun 11, 2019 at 18:05

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