Multiwire branch circuits

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fbuckland9

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I came across the multiwire circuits and it appears that now a double pole breaker is needed??? Is this correct? I know a breaker handle tie will also work for single pole breakers if this is the case. I just don't want to wire multiwire circuits and use single pole breakers if they are no longer allowed. Art. 240.15 B ; Exceptions 1-4 don't seem to make it acceptable to use single pole breakers, unless I am reading it wrong

I am rusty and going through the entire Mike Holt Exam Preperation books from the start. I passed my masters in 1997 on first attempt but whenI shelfed it in 2001, I missed my shelf fee in 2004 as I moved several times and didn't recieve my mail. So here I am going back through the refresher coarse offered by Mike and I am really enjoying it so far. It is amazing the things we forget and new items that come along after we are finished schooling. I am looking forward to sitting next month and passing my exam again.

Thanks for the help with this multiwire circuit question.
 

Little Bill

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Location
Tennessee NEC:2017
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Semi-Retired Electrician
I came across the multiwire circuits and it appears that now a double pole breaker is needed??? Is this correct? I know a breaker handle tie will also work for single pole breakers if this is the case. I just don't want to wire multiwire circuits and use single pole breakers if they are no longer allowed. Art. 240.15 B ; Exceptions 1-4 don't seem to make it acceptable to use single pole breakers, unless I am reading it wrong

I am rusty and going through the entire Mike Holt Exam Preperation books from the start. I passed my masters in 1997 on first attempt but whenI shelfed it in 2001, I missed my shelf fee in 2004 as I moved several times and didn't recieve my mail. So here I am going back through the refresher coarse offered by Mike and I am really enjoying it so far. It is amazing the things we forget and new items that come along after we are finished schooling. I am looking forward to sitting next month and passing my exam again.

Thanks for the help with this multiwire circuit question.

Welcome to the forum!

It clearly states in 240.15(B)(1) that handle ties are permitted. This is from the 2011

(1) Multiwire Branch Circuits. Individual single-pole circuit
breakers, with 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.

The 2008 says "with or without" handle ties but not many states/areas are using the 2008.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
IMHO, if you're doing new work then I would say that a 2-P breaker or s/p's with a handle tie is required. However, if you're doing a service upgrade and have existing MWBC's I don't see how you can be compelled to use 2-P breakers unless your municipality has a specific ordinance or requirement.
 

kwired

Electron manager
Location
NE Nebraska
Multipole (there are three phase MWBC's that use all three phases and a neutral) breakers or handle ties are permitted.

My past experiences with two pole QO breakers is that they cost about the same as two single pole breakers and a handle tie identified for the purpose. They do make three pole handle ties for the QO series, not sure how those come out price wise as I haven't ever used any, three pole breakers are usually pretty pricey over three single pole breakers though.

The advantage of the handle tie is if one pole trips the others will remain on, unfortunately the others will have to be shut off during the process of resetting the tripped pole. With multipole common trip breakers, if one pole trips they all trip.
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
The advantage of the handle tie is if one pole trips the others will remain on,
That's probably true with internal trip type breakers. However, breakers like CH tan handle move all the way off when tripped and will shut both poles. So, you have to ask the question "With internal trip breakers tied together with handle ties, what's the purpose of using the handle tie other than shutting off both poles when you're working on that circuit?"
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
The advantage of the handle tie is if one pole trips the others will remain on,
I agree, that's probably true with internal trip type breakers. However, breakers like CH tan handle move all the way off when tripped and will shut both poles. So, you have to ask the question "With internal trip s/p breakers tied together with handle ties, what's the purpose of using the handle tie other than shutting off both poles when you're working on that MWBC circuit?"
 

kwired

Electron manager
Location
NE Nebraska
That's probably true with internal trip type breakers. However, breakers like CH tan handle move all the way off when tripped and will shut both poles. So, you have to ask the question "With internal trip breakers tied together with handle ties, what's the purpose of using the handle tie other than shutting off both poles when you're working on that circuit?"
I guess there are some breakers that will trip other poles when a handle tie is used.

Though better terminology is "will take out with them" as the one pole experiencing the fault condition is the only one that actually tripped. This would be more common with any breaker series that doesn't have a mid position trip position.

Otherwise shutting off both poles when you want to open the circuit I'd say is the reason for a handle tie. The QO series multipole or any other larger frame units that only have a single handle still has a tie between poles it is just internal. They all have trip mechanisims on each individual pole and a common trip mechanism to trip all poles when only one pole sees a trip condition.
 
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