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#2399 - 07/06/01 06:55 PM Split circuits?  
bhester  Offline
Joined: May 2001
Posts: 38
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!

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#2400 - 07/06/01 07:13 PM Re: Split circuits?  

>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?

#2401 - 07/06/01 07:21 PM Re: Split circuits?  
bhester  Offline
Joined: May 2001
Posts: 38
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?

#2402 - 07/06/01 08:39 PM Re: Split circuits?  

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.

#2403 - 07/06/01 08:58 PM Re: Split circuits?  
Tom  Offline
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
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?


Few things are harder to put up with than the annoyance of a good example.

#2404 - 07/06/01 10:09 PM Re: Split circuits?  
bhester  Offline
Joined: May 2001
Posts: 38
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.

#2405 - 07/06/01 10:23 PM Re: Split circuits?  
Bill Addiss  Offline
Joined: Oct 2000
Posts: 3,878

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.


#2406 - 07/06/01 10:38 PM Re: Split circuits?  

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.

#2407 - 07/06/01 10:45 PM Re: Split circuits?  
bhester  Offline
Joined: May 2001
Posts: 38
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.

#2408 - 07/07/01 01:02 AM Re: Split circuits?  
amp-man  Offline
Joined: Jun 2001
Posts: 141
Sacto, California US of A

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...

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