ECN Forum Forums General Topics of the Trade General Discussion Area Split circuits?

12-3 home runs are not uncommon, per 210-4
what's the big deal?


1/2 my biz comes from DYI'ers as described, i'm always torn bettween ratting them out to the Fire Marshal, or sending them an X-mas card...

No big deal ,I see nothing wrong with it ,it wasn't the way I was trained and in my area it's not a common practice.I can tell you this that my next house will have some 12-3 homeruns espicially the way it was built,2x12 for rafters, sure makes it a little more time consuming for drilling.

O.k.,I want to make sure by doing this that I don't overload the neutral ,how many openings do you put on a circuit when sharing the neutral.As long as I keep them off the same phase can I load my circuit as normal .I usually put 12 openings on a circuit depending on loads for fixtures,I have taken a 2 year break from electrical work and just wanting to make sure I understand everything before I do anything.Thanks

bhester,

You've got a lot of good answers for your Q's here - many talented persons in this forum!!!

Maybe this little bit 'o information can help with your last question[s]:

1: As far as circuitry on the 3 wire circuit [basically the home run portion, using the 12/3 NM cable], if you can measure 220 - 240 volts between the black and red wires, then you have setup the homerun circuit OK. That's what you want to have so the grounded conductor [AKA Neutral] does not get overloaded.
In a case where you are using "stacked twins" [4-20 amp 1 pole breakers connected to only two bus poles], then you could connect two seperate 3 wire home runs on the frame, making sure there's 240 volts between the black and red on each home run.
[just threw that in for an FYI ].

2: Glad to see that you are planning to limit the maximum number of outlets per circuit!!
NEC does not limit the number of General Purpose [convenience] type receptacles per circuit on the typical single family dwelling, but that's no reason to follow the "Bare-Bones Minimum" of the NEC! Limiting the number of Receptacles is good design. This is the same on any type of circuit [AKA 2 wire circuit or 3 wire circuit].
For lighting, design the circuit[s] so they will not be overloaded if all lights were on at the same time, plus the largest lamp was used [if medium based screw shell fixtures, rate fixture at no less than 150 va].

3: Be sure to connect the circuits so they work on 1/2 the 3 wire [multiwire] circuit properly. This means keep the grounded conductors' connections uniform throughout their circuitry.
Maybe another member can explain this better!

Basically, the multiwire circuit will be the same as any typical 2 wire circuit, just that the common grounded conductor needs to be spliced and tapped more solidly, plus the need to have the ungrounded conductors connected across both lines - in order to avoid overloading the common grounded conductor [common Neutral].

Please excuse the "Outer Space" explainations! Feel free to comment if needed.

BTW / FYI to the rest of the group:
BBC America had a Monty Python Marathon all day on the 4th!!! Made sure to record a good 6 hours of it!!!
I'll be using said video tape for refresher course, then attempt to toss a few 1 liners here and there

Scott SET

Thanks for everyones' information,I really enjoy learning new things especially if it saves time and money and done correctly.

Every single house that I've done work on in my area has at least one 12/3 shared cable run across the attic. It saves a little on material costs and pulling time. For homebuilders doing 6-24 homes at a time it saves them a fair amount in the long run.

Ni

Bring me a Shrubbery!!! I fa*t in your general direction

Scott SET

P.S. I will not buy this record, it is scratched!
I will not buy this Tobacconist, it is scratched!
My hovercraft is full of eels!

Well gang as youy can tell by my post in here I am no expert but if there was one thing I could change in the code or any where else it would be what you call split or multi wire circuits, you cannot blame screwups just on the DIY'R, just got done beingnearly knocked out of a man lift because of a PROFESSIONAL running a multi wire circuit and not tying or marking the breakers when the neutral was disconnected there was such a load that it blew a hole in the J-box bigger than a quarter not only was i blinded for about 4 minutes I had 3 fingers severly burned found that they had put a 40 amp breaker used # 12 wire and had 38 amps running on that circuit. Saves wire yes it does is it save not in my opinion just my thoughts