Multi wire branch circuits

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UPMICHIGAN

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Hello all!

Electrical contractor from Michigan here. I was red tagged on a job today 9-1-22 for installing MWBC. Had a job that required the main panel be relocated since it was in a bathroom. I relocated the panel to the new addition and installed a 2” conduit from the new panel to the previous panel location and converted the old enclosure to a j box. In order to keep de rating to a minimum I pulled MWBC and handle tied the breakers. Inspector said “common” neutrals are not allowed because because of one breaker trips it trips the other breaker it is handle tied to. I politely asked him to show me the code that says this and not surprisingly he couldn’t find one. By the time he left he said “he guesses I don’t have to change all the circuits, just the kitchen and bathroom circuits can’t be MWBC”. Again I asked for a code reference and he left. Who is right here? Thanks for your thoughts
 
There is no rule prohibiting MWBC's. That said however, due to AFCI's required almost everywhere, they are often not practical to use in a resi setting. Also he is wrong that a handle tie will trip the other side. That is not what a handle tie does or is for.
 
electrofelon said:
There is no rule prohibiting MWBC's. That said however, due to AFCI's required almost everywhere, they are often not practical to use in a resi setting. Also he is wrong that a handle tie will trip the other side. That is not what a handle tie does or is for.
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Thank you for your reply!! I told him the same thing about handle ties and he said I’m completely wrong! I’ve actually never watched a handle tied breaker trip before so I didn’t have experience to back up my statement. But I was always told that they didn’t trip the other breaker. And for what it’s worth, Michigan doesn’t require AFCI protection. Anyway, thanks for the reply!
 
UPMICHIGAN said:
Inspector said “common” neutrals are not allowed because because of one breaker trips it trips the other breaker it is handle tied to. I politely asked him to show me the code that says this and not surprisingly he couldn’t find one. By the time he left he said “he guesses I don’t have to change all the circuits, just the kitchen and bathroom circuits can’t be MWBC”
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This inspector is clueless. A MWBC can be protected by either single pole circuit breakers with handle ties or a multi-pole circuit breaker. If tripping both circuits is not permitted then how can you use a multi-pole CB?
 
Inspector wrong on a couple of counts. If the circuits in question were not required on the upgrade/change to be AFCI, then complications due to MWBC are limited and infact "Must" be capable of simultaneously disconnecting both branch circuits. One method approved is the handle ties or a 2p breaker is another. 210.4(B) as already stated. The factual basis of handle tied circuit one tripping will not trip the other however a manually shutting off will as required by 210 shut off both.
His final giving in to state regarding the kitchen and bath has some value in that those circuits cannot be mixed with other non area wiring. Bath must be on it's own with no other outlets, so to share the neutral is putting another set of outlets onto the branch circuit. Same with kitchen, unless they are all kitchen circuits, can't share with a different space, limited by 210.52(B)(1)&(2). Complication related to GFCI requirements within the spaces "may" make for problems for neusence tripping of the GFCI devices.
 
Fred B said:
His final giving in to state regarding the kitchen and bath has some value in that those circuits cannot be mixed with other non area wiring. Bath must be on it's own with no other outlets, so to share the neutral is putting another set of outlets onto the branch circuit. Same with kitchen, unless they are all kitchen circuits, can't share with a different space, limited by 210.52(B)(1)&(2)
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Are you saying that a MWBC can't supply one circuit in a bathroom and the other circuit somewhere else?
 
infinity said:
This inspector is clueless. A MWBC can be protected by either single pole circuit breakers with handle ties or a multi-pole circuit breaker. If tripping both circuits is not permitted then how can you use a multi-pole CB?
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Thank you for taking the time to reply. He kept saying “because they are handle tied they are now “two phase”!! 😂. I said “this is a single phase system!!!” You can’t get two phase if you tried
 
UPMICHIGAN said:
Thank you for taking the time to reply. He kept saying “because they are handle tied they are now “two phase”!! 😂. I said “this is a single phase system!!!” You can’t get two phase if you tried
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Obviously this inspector need to brush up on code and electrical theory.
 
electrofelon said:
Also he is wrong that a handle tie will trip the other side. That is not what a handle tie does or is for.
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I'm not sure if I totally agree but I need some clarification. There are some s/p breakers that trip all the way off (i.e CH tan handle) as opposed to an internal trip breaker which trips to a center position. If handle ties are used on the center trip type breakers then I agree that the handle tie probably won't trip the other breaker. However, in the case of the CH breaker I believe it will trip the other breaker. Please correct me if I'm wrong.

If I'm understanding the purposes of handle ties, they are used to insure that both MWBC circuits can be shut off while working on them. On the other hand, if only one of the circuits trips on a short or overload, doesn't the same hazard exist if you didn't use handle ties ?
 
Fred B said:
Inspector wrong on a couple of counts. If the circuits in question were not required on the upgrade/change to be AFCI, then complications due to MWBC are limited and infact "Must" be capable of simultaneously disconnecting both branch circuits. One method approved is the handle ties or a 2p breaker is another. 210.4(B) as already stated. The factual basis of handle tied circuit one tripping will not trip the other however a manually shutting off will as required by 210 shut off both.
His final giving in to state regarding the kitchen and bath has some value in that those circuits cannot be mixed with other non area wiring. Bath must be on it's own with no other outlets, so to share the neutral is putting another set of outlets onto the branch circuit. Same with kitchen, unless they are all kitchen circuits, can't share with a different space, limited by 210.52(B)(1)&(2). Complication related to GFCI requirements within the spaces "may" make for problems for neusence tripping of the GFCI devices.
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Thank you Fred for your reply!
 
goldstar said:
I'm not sure if I totally agree but I need some clarification. There are some s/p breakers that trip all the way off (i.e CH tan handle) as opposed to an internal trip breaker which trips to a center position. If handle ties are used on the center trip type breakers then I agree that the handle tie probably won't trip the other breaker. However, in the case of the CH breaker I believe it will trip the other breaker. Please correct me if I'm wrong.

If I'm understanding the purposes of handle ties, they are used to insure that both MWBC circuits can be shut off while working on them. On the other hand, if only one of the circuits trips on a short or overload, doesn't the same hazard exist if you didn't use handle ties ?
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Thank you for your reply! I installed SQD Homeline breakers. Which as I’m sure you know do have a center tripped position. I’m going to be providing him with manufacture data on these handle ties. I’m honestly a bit frustrated with him
 
infinity said:
Are you saying that a MWBC can't supply one circuit in a bathroom and the other circuit somewhere else?
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Only to the extent that it complies with 210.11(C)(3).
The neutral is part of the circuit wiring thus part of "the branch circuit", and should be considered in when determining "shall have no other outlet" requirement of that article.
 
Fred B said:
Only to the extent that it complies with 210.11(C)(3).
The neutral is part of the circuit wiring thus part of "the branch circuit", and should be considered in when determining "shall have no other outlet" requirement of that article.
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You have an interesting way of looking at things.
I've never considered MWBC it that way, but technically you're partly right.

Following along technically....
not only should the neutral be considered, so should the hot.

Suppose it's a 12/3 NM
It's not a multi circuit cable
It's a single circuit consisting of multiple hots sharing a neutral

As for electrical flow, the neutral is only involved on the unbalanced portion. Both hots carry the balanced portion.

So the red wire is part of the same circuit as the black.

But that's not the intent.
Just another time where the technical wording gets in the way of the intended meaning.
 
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