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Hello everyone, this is my first post, looks like a lot of great info on here. Short bio is...I'm located in Ontario and my field of work is traffic signals and operations.

Not related to the above; I opened up a couple of walls in a house I was working on the side and found that the guy had wired a split for his basement lighting. It works, no worries there, but why would someone do this. It seems like a waste of space in the panel. Just thought I would share.

Basically he has 10 cans on one circuit breaker (no problem there), but then he uses a split circuit to run another 9 set of cans seperated it 4 and 5. What baffled me was that the breakers are integrally tied so if you shut off 5 set of lights the other 4 set go out and vise vera obviously. Anyway, kind of made me chuckle. Anyone ever see this setup before?

 

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1st, let me compliment you on a nice drawing.

In the states, it's a code rule now that a MWBC (Multi Wire Branch Circuit) (what you are calling a split circuit) must disconnect both ungrounded conductors when switching off the circuit breaker. This is for safety reasons to try to protect people that shouldn't be working on electrical stuff from hurting themselves (that's not you is it?). My guess is Canada has a similar requirement.
 

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Hello everyone, this is my first post, looks like a lot of great info on here. Short bio is...I'm located in Ontario and my field of work is traffic signals and operations.

Not related to the above; I opened up a couple of walls in a house I was working on the side and found that the guy had wired a split for his basement lighting. It works, no worries there, but why would someone do this. It seems like a waste of space in the panel. Just thought I would share.
Basically he has 10 cans on one circuit breaker (no problem there), but then he uses a split circuit to run another 9 set of cans seperated it 4 and 5. What baffled me was that the breakers are integrally tied so if you shut off 5 set of lights the other 4 set go out and vise vera obviously. Anyway, kind of made me chuckle. Anyone ever see this setup before?

Not sure about Canada but in the US if it is a multiwire branch circuit (split circuit as you called it) then you must have a dp breaker or use 2 sp breakers with handle ties.

Other than using more circuits than needed the hookup is fine
 

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It's very common and there's nothing wrong with it. It can be done using individual breakers which do not turn off the other leg. The primary advantage is having two circuits contained in a single cable so you can complete the installation faster. Other benefits include fewer neutrals and grounds to terminate in the panel and less voltage drop on long runs.

I haven't done residential lately but I used to always try to use a 3-wire home run whenever possible/legal/practical. It's even more common in commercial.

In this case for the amount of load having three 15A circuits might overkill but we don't know the actual load.
 

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My guess is Canada has a similar requirement.
Nope only if the circuit is powering split receptacles with one circuit on the top half and the other on the bottom half.

Also to the OP, it is not called a "split circuit", the correct term is multi-wire branch circuit. You might be calling it a split circuit because in a Canadian house the most common application for these was for a long time, kitchen countertop split receptacles. They can be used for whatever though.
 

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Discussion Starter · #6 · (Edited)
Good discussion guys. Thanks for all the replys. I am aware that its called a MWBC, my future posts will be written with technical jargon.

I guess what I was trying to get at is that he put 10 pot lights on one circuit and then split the other 9 on two. This could have been achieved by running 14/2 and splicing the hot to each light switch at the device box.
 

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Vintage Sounds said:
It's very common and there's nothing wrong with it. It can be done using individual breakers which do not turn off the other leg. The primary advantage is having two circuits contained in a single cable so you can complete the installation faster. Other benefits include fewer neutrals and grounds to terminate in the panel and less voltage drop on long runs. I haven't done residential lately but I used to always try to use a 3-wire home run whenever possible/legal/practical. It's even more common in commercial. In this case for the amount of load having three 15A circuits might overkill but we don't know the actual load.
Not in my area, three wire requires double pole. If your working on the circuit you could break neutral for other circuit , no no here to use single pole on MWBC in resi.
Inspection counts three wires and you better have that many double poles.
 

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eddy current said:
Do you have any bulletins or code # for that ?
Not right now, just got out of school board meeting . Can't remember what rule he quoted off hand . Something to do with creating a hazard. Sorry , your right! " no rule , not true" :) See what I can dig up tomorrow.
School board meeting was a waste of time too.
Lazy bas***ds.
 

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Not in my area, three wire requires double pole. If your working on the circuit you could break neutral for other circuit , no no here to use single pole on MWBC in resi.
Inspection counts three wires and you better have that many double poles.
I have to say I used to live and work in the Toronto area and never encountered this. We used to stick single poles on MWBCs in houses all the time. Not saying you're wrong but I never had an inspector who had a problem with it. The only rule in the book I could find is 14-010. I think though that there's been some debate on this forum about whether the wording of the rule requires a handle tie or two pole breaker if the circuit contains both lighting and receptacles.

14-010 Protective and control devices required
Electrical apparatus and ungrounded conductors shall, except as otherwise provided for in this Section or in other
Sections dealing with specific equipment, be provided with

(b) manually operable control devices that will safely disconnect all ungrounded conductors of the circuit at
the point of supply simultaneously, except for multi-wire branch circuits that supply only fixed lighting
loads or non-split receptacles, and that have each lighting load or receptacle connected to the neutral and
one ungrounded conductor
 

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I agree with you vintage. In 3 phase it is also done all the time. Only time you need a tie bar is if the two (or three) circuits are for the same device. Here's an explanation from the Simplified book on 14-010
Sorry, bad pic but it says we have 3 choices. 2 pole breaker or 2 single pole with a tie bar or 2 single pole without tie bar. There's another diagram on the next page for a 3 phase panel, same deal. We do not need tie bars


 

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eddy current said:
I agree with you vintage. In 3 phase it is also done all the time. Only time you need a tie bar is if the two (or three) circuits are for the same device. Here's an explanation from the Simplified book on 14-010 Sorry, bad pic but it says we have 3 choices. 2 pole breaker or 2 single pole with a tie bar or 2 single pole without tie bar. There's another diagram on the next page for a 3 phase panel, same deal. We do not need tie bars
Sorry , rule I found was 14-302, if I understand it correctly says you can use single poles BUT , you need to tie them together.
Which I think IMO is to provide separate over current production even though they are tied together, where as a double pole is common trip.
And would kill both circuits.
Could be wrong , wouldn't be the first time:)
 

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Good discussion guys. Thanks for all the replys. I am aware that its called a MWBC, my future posts will be written with technical jargon.

I guess what I was trying to get at is that he put 10 pot lights on one circuit and then split the other 9 on two. This could have been achieved by running 14/2 and splicing the hot to each light switch at the device box.
The cir from the panel is a mwbc
 

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So am I wrong then?
Not sure what you mean :)
I mean just exactly what I said. Interpreting the code can be a pita but the code rule you quoted sent you to another code rule. Never to return to the rule you just left. In fact you never even got to finish reading=g that code rule.

Like a computer program. Do this, Do this, If this, then do that.
 
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