Multiwire branch circuits

[knoppdude]

I wired double duplex receptacles in a small laboratory with another electrician, with each receptacle having one ungrounded conductor, and a common neutral with the other. I know that 210.4(B) states that the use of a two pole breaker, or two breakers with a handle tie are only required if the circuit(s) terminate on a device on one yolk, but is it necessary to use a common trip breaker in a situation where a multiwire branch circuit terminates to two separate receptacles in a common junction box? HOpe this question is not too mundane. Thanks.

 

[roger]

I wired double duplex receptacles in a small laboratory with another electrician, with each receptacle having one ungrounded conductor, and a common neutral with the other. I know that 210.4(B) states that the use of a two pole breaker, or two breakers with a handle tie are only required if the circuit(s) terminate on a device on one yolk, but is it necessary to use a common trip breaker in a situation where a multiwire branch circuit terminates to two separate receptacles in a common junction box? HOpe this question is not too mundane. Thanks.

What code cycle are you reading?

Read 210.4 and 210.7 in the 2008 for your answer

Roger

 

[e57]

I wired double duplex receptacles in a small laboratory with another electrician, with each receptacle having one ungrounded conductor, and a common neutral with the other. I know that 210.4(B) states that the use of a two pole breaker, or two breakers with a handle tie are only required if the circuit(s) terminate on a device on one yolk, but is it necessary to use a common trip breaker in a situation where a multiwire branch circuit terminates to two separate receptacles in a common junction box? HOpe this question is not too mundane. Thanks.

We're not on the '08 NEC yet.... Next January the MWBC will need a handle tie in all situations apart from existing circuits done the 'old skool - not dumbed down way', but for us in CA (Still 05 NEC/07 CEC) if two circuits were to the same yoke (the same recpt.) - it needs a handle tie... Otherwise the method you decribed (Two different recept's or circuits in one box) is compliant for the time being....

One cavet though is that the neutral would need to be pigtailed, the neutral connection can not be dependent on the device connections..... So a pig-tailed neutral from the common neutral would be going to each.

 

[knoppdude]

e57, you are right about the 2005 NEC allowing separate breakers for the ungrounded conductors of MWBC's that do not terminate on a device on one yoke. Unfortunately, all we had at our disposal was the 2008 NEC, which if I read 210.4(B), states explicitly that each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates. In my opinion, this would allow no exception. The other electrician then cited 240.15(B)(1), which would allow separate breakers for each ungrounded conductor. As California is still on the 2005 code cycle, I dug out Mike Holts understanding the 2005 NEC, and separate breakers without a means of simultaneous disconnect are allowed. I was wrong based upon the 2005 NEC, but now reading 240.15(B)(1), of the 2008 NEC, it seems that this section should have been removed, as I don't see any exception to 210.4(B). I know this is splitting hairs, but for the 2008 NEC, I don't see any situation where 240.15(B)(1) can be applied.