There’s a 12/3 existing wiring in my hallway that runs up to the light fixtures. I want to extend the 12/3 wiring to a bedroom to add a smart switch and recessed lighting. If I pigtail 12/3 from the power in going to the light switch in the hallway and send the cable to the bedroom to a smart switch would that work?enter image description here

  • What power is already in the bedroom? Can you provide pictures of the switch box you want to run power from?
    – JACK
    Sep 5 '20 at 17:34
  • Can you post photos of the inside of the switch box in the hallway please? Sep 5 '20 at 17:39
  • The bedroom only have black, white and ground, whereas in the hallway there is white, black, red and ground.
    – varhsb
    Sep 5 '20 at 20:00

First thing is you need to determine if that box (picture) is two circuits with a shared neutral, called a MWBC. You weren't clear what lights are on that box, and what lights you are going to have on the smart switch. I presumed the smart switch is going to control the recessed lights and all that is going to be in the bedroom? What do you have to test voltage with? (How much is already on the circuit/circuits?) If it is split (MWBC), then you will only be using one circuit (a hot and a neutral). Warning, you must have BOTH circuits turned off before you do this (or you can blow something up on the live circuit! You could also get electrocuted.

Do NOT mistake the red wire in your box (pic) for the Red wire in a smart switch diagram!

[UPDATE-adding question (can't comment yet, until I get 2 more up-votes)]

Did you mean 12-2 wire? 12-3 has a black, red, and white wire; 12-2 has black and white. 12-3 w/g (with ground) has black, red, white, and bare ground. If you mean 12/2 G, then your project makes more sense to me.

Also, mostly curiosity; is that box (pic) mounted on a stud? It looks like the drywall is patched on all four sides. I would recommend adding 'F' clips, but the plaster ears are not on that box,as far as I can tell. (and that patch looks wafer thin anyway at the ear ends.) So does the switch fit in that box? Looks like it is in another box, no room here, and no pigtails visible...

If you meant 12/2, then my advice above is still applicable.

@FreeMan Thanks for the assistance, fixed those in my post.

  • 1
    Please don't put a signature in your answer, especially one that's different than your user name. The signature that's now in the middle of the post makes it look like you're addressing someone else and is very confusing. Also, I'd advise you to change your last sentence to use the word "advice".
    – FreeMan
    Sep 9 '20 at 17:21

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