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MWBC with line-neutral AND line-line loads

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    MWBC with line-neutral AND line-line loads

    Can I put both line-neutral AND line-line loads on a single MWBC. Got a home shop that needs 120V and 240V receptacles throughout. Some of the equipment (e.g. band saws, table saws) runs on 240. Some runs off 120. Generally no two pieces of equipment will be on at the same time. Thinking about putting a single MWBC to power it. 2017 NEC. 210.4.C says "MWBC shall supply only line-neutral loads", but exception 2 says "When all ungrounded conductors of the MWBC are opened simultaneously by the branch-circuit overcurrent device". Given that 210.4.B already requires that all ungrounded conductors be simultaneously disconnected, isn't 210.4.C completely moot/irrelevant?

    #2
    Maybe it is about common trip and not just handle tie.

    Comment


      #3
      Originally posted by rszimm View Post
      Given that 210.4.B already requires that all ungrounded conductors be simultaneously disconnected, isn't 210.4.C completely moot/irrelevant?
      Being "disconnected" and being "opened simultaneously by the branch OCD" are different things, so 210.4(C) isn't moot.

      Two or three single pole circuit breakers with a handle tie would accomplish the first but not the second.

      A two pole or three pole circuit breaker would accomplish both.

      Edit: Or what Sierra said

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        #4
        Of course. Great point. OK, so is there anything else in the code that I'm not thinking of that would prevent a mixture of line-line and line-neutral loads on the same MWBC?

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          #5
          210.4(C) Line-to-Neutral Loads. Multiwire branch circuits
          shall supply only line-to-neutral loads.
          The more they overthink the plumbing, the easier it is to stop up the drain

          Comment


            #6
            Even if it's permitted, it sounds like a poor design IMHO.

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              #7
              Originally posted by rszimm View Post
              Of course. Great point. OK, so is there anything else in the code that I'm not thinking of that would prevent a mixture of line-line and line-neutral loads on the same MWBC?
              A mixture of line-line and line -neutral loads occur all the time.

              Think of Range or Dryer circuits for example, or, even a 120/240v panel in itself.

              Just be careful what you call the circuit and be mindful of the OCPD installed ahead of the conductors.


              JAP>

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                #8
                Originally posted by dkidd View Post
                210.4(C) Line-to-Neutral Loads. Multiwire branch circuits
                shall supply only line-to-neutral loads.


                Originally posted by rszimm View Post
                2017 NEC. 210.4.C says "MWBC shall supply only line-neutral loads", but exception 2 says "When all ungrounded conductors of the MWBC are opened simultaneously by the branch-circuit overcurrent device".

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                  #9
                  Originally posted by david luchini View Post
                  Now allowed.
                  Master Electrician
                  Electrical Contractor
                  Richmond, VA

                  Comment


                    #10
                    Originally posted by LarryFine View Post
                    Now allowed.
                    Why do you say that? It would seem Exception 2 applies here.

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                      #11
                      Originally posted by rszimm View Post
                      Why do you say that? It would seem Exception 2 applies here.
                      It does when you use a mulit-pole circuit breaker.
                      Rob

                      Moderator

                      All responses based on the 2014 NEC unless otherwise noted

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                        #12
                        Originally posted by rszimm View Post
                        Why do you say that? It would seem Exception 2 applies here.
                        Read the exception again. Only line-to-neutral loads unless protected by a breaker that assures simultaneous opening of all lines.
                        Master Electrician
                        Electrical Contractor
                        Richmond, VA

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                          #13
                          Yeah, so just a typical 2 pole breaker.

                          Comment


                            #14
                            I would do everything in my power to talk them into a subpanel, rather than hooking a bunch of 120v and 240v receps to the same circuit.

                            Comment


                              #15
                              Originally posted by Cow View Post
                              I would do everything in my power to talk them into a subpanel, rather than hooking a bunch of 120v and 240v receps to the same circuit.
                              What will it add for a 4 circuit main lug panel? Maybe $100? Not worth the time thinking about it.
                              Tom
                              TBLO

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