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If I have a 240v 20a circuit serving a single 240v 20a receptacle (12/3) can I leave the 240v receptacle in service then branch two 120v 20a circuits from it?

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  • What make and model is your breaker box, and is the existing 20A breaker a full-size breaker or a double-stuff? – ThreePhaseEel Apr 26 '20 at 2:01
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    @ThreePhaseEel it's a square D QO and the existing breaker is full sized, two pole, single trip 20A. It's not. Double stuff, no clip, no tie. – Matthew Apr 26 '20 at 2:43
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Perhaps. Firstly, without a time machine you have a 240V 20A receptacle and want to add 120V 20A receptacles.

You may need to replace the breaker with a dual-pole GFCI breaker as it's quite likely that the 120V circuits will need GFCI protection depending where they are and what version of code is adopted in your area at the time you do the work.

Other than that, yes, this is fine.

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  • Thanks. This is for a circuit serving garage receptacles. I'm in California. – Matthew Apr 26 '20 at 1:54
  • The 2017 requires the receptacles in a garage to be GFCI, so the double pole GFCI would be needed with the change if CA adopted that requirement I think most states did for 15 and 20 amp circuits. – Ed Beal Apr 26 '20 at 3:01
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    Could I use gcfi receptacles instead of getting a gfci breaker? – Matthew Apr 26 '20 at 3:30
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    @Matthew Yes, you can use individual GFCI receps in each location. However anywhere the neutral is shared, you cannot use the LOAD terminals to protect any downline. So you may end up spending more on GFCI receps than you would on the breaker. – Harper - Reinstate Monica Apr 26 '20 at 4:40
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    Be sure to use a common trip breaker, not handle ties. The rules (NEC 210.4) say the disconnecting means must disconnect all line conductors, then says MWBCs can only feed line to neutral loads, then gives an exception that allows line to line if all ungrounded conductors are simultaneous disconnected by the overcurrent device. Seems like an insignificant difference, but it is often interpreted to exclude handle ties, because the overcurrent device isn't disconnecting the other ungrounded conductors, the handle tie is. – NoSparksPlease Apr 26 '20 at 16:24

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