House is in CA, built in 1974 using the MWBC setup.

From Main:

1) Has four single pole circuit breakers.
2) Four Hot running into house.
3) Two Neutral running into house.

A) Circuit #2 handles part of Kitchen as well as bedrooms 1 and 2:

-Kitchen ceiling light(switched)
-Two kitchen wall outlets/switches
-Outdoor light just outside of kitchen door(switched).

Each room includes:

-1 wall light (no wall switch-switched at the light itself)

-3 outlets with full load starting at 5pm. TV's, PC's, Monitors, Clock Radios's, DVD players, AND a wall air conditioner (120v/1150W). - Ya, Ouch, this setup is mirrored in room #2 on the same circuit. Double ouch.

Link to layout is:

http://www.pacificmusicpapers.com/AL_LAYOUT_1.pdf

The theory:

I want to run 2 x 12/3 lines from main; One run from Main connecting to room #1, the other run from Main connecting to room #2. I then want to cut off the head of the snake in the kitchen, leaving the kitchen items, mentioned above, the ONLY items on circuit 2.

The snag (avoiding costs):

I want to have the 12/3 run's supply bedroom #1's outlets/light; The RED for the Air Conditioners (120v/1150w) outlet ONLY and the BLACK for the rest of the room.

Duplicate in room #2 using 2nd run of 12/3.

The question:

Can I use single pole switches for this or do I need to use double? And if single, do I need to stagger them on separate legs?

"The question:

Can I use single pole switches for this or do I need to use double? And if single, do I need to stagger them on separate legs?"

EDIT:

Replace word "switches" with "circuit breakers".

I believe Ca is under the 2008 NEC or some form of it. This requires the use of a tied breaker for multi-wire3 circuits.
Code or not, it is a good idea.

Single pole breakers would be your best bet. If you use a dbl pole and the air conditioner for some reason trips a dbl pole breaker, you just may be in the dark since they are mechanically linked to trip together.

But, is there any reason you are not using separate runs, ie; 12-2 X 4 rather than 12-3 X2? Using 12-3 is fine, but whenever you share a neutral there is always a chance of overloading it. Keeping them on separate phases will alleviate that problem.

If you put the breakers next to each other, they will be on separate legs, in MOST panels.

Single pole breakers would be your best bet. If you use a dbl pole and the air conditioner for some reason trips a dbl pole breaker, you just may be in the dark since they are mechanically linked to trip together.

But, is there any reason you are not using seperate runs, ie; 12-2 X 4 rather than 12-3 X2? Using 12-3 is fine, but whenever you share a neutral there is always a chance of overloading it. Keeping them on seperate phases will alleviate that problem.

If you put the breakers next to each other, they will be on seperate legs, in MOST panels.

Stan, I think, is correct regarding the code here in CA as of 2008. I don't think I'll pass using single pole, however this may only apply if I'm hooking up one piece of equipment to two circuits (i.e. an electric stove), but a simple trip to my local inspector will answer that (small suburb of LA-no lines, no hassle, immediate answers.. ya, nice, I know.)

Now, for the last 20 minutes I've been wondering why I don't just run 12/2 x 4 as you mentioned and the simple answer is--hassle up in the attic, more wires to contend, time and cost. Other than that, none. However, using 12/2 x 4 will allow for future growth in the event the AC's they have are removed from the wall (which has happened with them before in another room leaving a nice pretty faceplate in the middle of the wall.)

Was looking at the 2008 NEC. Was confronted with the AFCI issue. Now, they're talking about how AFCI can not be used using Multiwire setup. Although Cutler makes a double pole for that application I'm reading conflicting information. So, the next two questions would be:

1) Is AFCI needed in my application given I'm only running to an existing junction box in the attic (see above link to PDF.)

2) If AFCI is needed, then will I have to run 14/2 x 4 rather than 14/3 x 2. Also, what is the diff between an AFCI CB and a "Combination AFCI CB".

Thanks in advance,

ADG