2008 Nec Mwbc

[Twoskinsoneman]

Help me undertand what the purpose of this code is.

240.15 (b)(1) Multiwire Branch Circuit. Except where limited by 210.4(B), individual single-pole circuit breakers, with or without identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads.

210.4(B) Disconnecting Means. 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

It seams like 240.15 (b) is saying "you don't necessarily HAVE to have "identified handle ties" unless 210.4(b) says you do...WHOOPS looks like it DOES say it hahahha."

 

[iwire]

I think they needed to leave an option for MWBCs that are supplied from old fuse panels.

 

[Twoskinsoneman]

I think they needed to leave an option for MWBCs that are supplied from old fuse panels.

Could you expand on this a little? I'm trying to understand what you mean....
this is the meat of 240.15 (b)(1) "individual single-pole circuit breakers, with or without identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits..."

limited by

"(B) Disconnecting Means. 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."

I guess what I'm getting at is there doesn't seem to be any situation where your MWBC can have "single-pole circuit breakers...without identified handle ties..."

 

[brother]

Could you expand on this a little? I'm trying to understand what you mean....
this is the meat of 240.15 (b)(1) "individual single-pole circuit breakers, with or without identified handle ties, shall be permitted as the protection for each ungrounded conductor of multiwire branch circuits..."

limited by

"(B) Disconnecting Means. 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."

I guess what I'm getting at is there doesn't seem to be any situation where your MWBC can have "single-pole circuit breakers...without identified handle ties..."

you are correct, i had brung up this issue before. this was a basically an OVERSIGHT of the CMP. see post 5 from this link http://forums.mikeholt.com/showthread.php?t=94506

Article 210 is CMP 2 and 240 is CMP 10. This was a correlating issue that was missed in this code cycle. I was at class with the chairman of CMP 10 last week and he said this will be corrected in the next cycle.
Don