My house was built in the late 50's. The upstairs has 3 bedrooms and a bath. I'm currently putting an addition on and am increasing the size of two bedrooms. These rooms are gutted out, and I'm taking this opportunity to place each room on their own 15 amp circuit (roughly seven receptacles and one ceiling light are needed). After gutting, found the entire upstairs is powered by one 12/3 wire (220v?) which is hooked into 2-20amp circuit breakers.

My question is, would it be okay to take that existing 12/3 line into an accessible junction box and run power to the old bedroom off one power wire and bathroom off the other power wire, tying all three neutrals together? Then proceed with my plan of placing the two enlarged bedrooms on their own circuits?

 

Some areas require that bedrooms be protected via a ACFI breaker, and I believe you can't use a shared neutral circuit (like you have, which should have a double pole breaker in the panel). If you have everything gutted out you may as well run 2 new circuits (I prefer 20A over 15A). The bathroom should be on its own 20A circuit.
Since you're doing extensive remodeling/addition you will probably have to bring any area you're working on up to existing code.

 

I'm sorry, I gave the wrong impression. Just the two enlarged bedrooms are gutted. The other bedroom and bathroom are not, and putting new circuits into them is not in my current plans. I also spoke to my building inspector, and he said while my municiplality is in the process of adopting some type of code, my building permit was issued prior to this, so I think I'm okay on the code related issues. He told me an electrical inspection is not required, although I plan on bringing someone in anyway.

With this added info, are there problems with my original plan?

 

Your plan for utilizing a 12/3 Branch-Circuit cable to supply 2 seperate 20 amp circuits is in compliance with the NEC. Yes , the 3 White wires connect together where the 12/3 cable "divides".------Good Luck!!!

 

Thanks for the info. After reviewing my situation, I am able to run an additional circuit for my other bedroom, but the existing circuit to the bathroom cannot be changed without a lot of additional demolition.

So one additional question. Is there a way I can cap off the red power wire, shutting this 20amp breaker off at the box, and use this 12/3 Branch-Circuit cable for just one circuit? Or is there more involved than this?