I've heard of several contractors that run 12/3 from the panel to the farthest room from the panel and split the circuit,red for one circuit and black for another.I understand that you wouldn't want these on the same phase but where my problem begins is now they have added a room addition on to the house and a DIY just attached to an existing circuit and now is overloaded.Actually it's not my problem but now the homeowners are upset about paying this DIY for all these problems,and he won't return there calls......imagine that!

>I understand that you wouldn't want these on the same phase
Actually, they must not be or the neutral will be overloaded.

>a DIY just attached to an existing circuit and now is overloaded.
Overloaded both halves?
Or was the original 12-2, not 12-3?

No,the overloaded circuit was on the 12-3 wire and I'm sure the other side of the 12/3 is at it's max as well.The circuit in reference has 22 plugs,Broan hvl(1600 w),6 recess cans(75w per),whirlpool tub and an outside plug and the owner called me to replace a bad breaker and after investigating other than at the panel I found the loaded up circuit.Are there others that do this and what are all the pros and cons?

The cons are heavily loaded circuits have more voltage drop and inadequate room for expansion.

No, what are you asking? There is nothing wrong with running a double-pole circuit from a breaker with the handles tied. It is two 20 A circuits with a shared neutral, and in my opinion, has slightly less voltage drop for normal loads than when not having a shared neutral.

The problem is that two circuit is obviously not enough.

You just describe at least a 50-70 amp load.
There are two circuits where five are needed.
Run some more cable. Two more runs of 12-3G would be a good start. If the distance is over 50' (wire length), use #10 for the heavier loads.

I've got to admit, i have very little sympathy for DIY'ers. Most of us would have run a circuit (maybe more) back to the panel. Just curious, did he do his own plumbing too?

Tom

I have over 17 years in residential and have seen this a time or two mainly in older kit circuits but as a young apprentice was exlained that it wasn't kosher.So as I was trained I moved on to doing things the way I was taught.I'm starting a 3700 Sq ft house and I'm going to have 4 circuits on the far side of the house,so would I just run 2 12-3 runs from the panel to the far side of the house. I know not to put the same wires on the same phase and to put on a 2 pole breaker.What my concerns are what kind of problems might I encounter by doing this as long as I don't overload the circuit.

bhester,

If you are going to run 3 wire to a receptacle box and split it there you have to connect all neutrals together and go to the receptacle with a tail. You must not use your receptacle to connect the neutrals. Everything else you seem to know.

Bill

What Bill is saying is that if you use the first receptacle box to split into two circuits, then you must pigtail that receptacle so that the neutral for the other circuit is connected back to the panel by a wire nut (rather than daisy-chained using the screws on the receptacle itself).

And if you run three wire to every receptacle box, then this applies at every such receptacle to make it less likely that the receptacles could be energized at 240 V.

Thanks ,I believe this will save alot of time on pulling wire.Is this a common practice elsewhere or is this something thats just done as needed.

bhester,

I use a multiwire circuit (12/3) to the kitchen. One side feeds the countertop outlets on one side of the kitchen, the other feeds the dishwasher disposal (on the same side of the kitchen). Also, I've run a 14/3 to supply two forced air gas furnaces next to each other.

By the by, the only time the code requires a handle tie or common trip breaker is when the two circuits are on the same yoke (like a split outlet). Some inspectors have insisted that I put in a handle tie because the two circuits are in the same box. It is a little safer for some goof who starts poking around in the j-box, and checks only one side of the multiwire...

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

bloody do-gooder!

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

No disrespect, doc, but multi-wire circuits are a fact of life. Especially by professionals. It is often amateurs who will run unnecesary neutrals. It is certainly safer to run the extra neutrals, but the reality is this requires larger conduits & boxes. The key is to be aware of multi-wire circuits. (That being said, I'll probably get hit again someday!!) As far as the 40A brkr, a screw-up,indeed.

Do GFCI receptacles tolerate multi-wire branch circuits? I've heard stories where they trip all the time? Any truth to those stories?

GFCIs have no problems with line side multiwire circuits. The only GFCI that will work with a load side multiwire circuit is a 2 pole 120/240 volt breaker.
Don(resqcapt19)