I'm putting in a basement bathroom with a macerator toilet, 3 lights, an exhaust fan, 2 switches and 4 outlets. I ran a new 12/3 cable from the distribution box across the basement ceiling ( no drywall yet) over to where the 2 switches are going to be. I need to know how to go from there to wire everything from that point.

Here's a diagram of the bathroom layout:

enter image description here

  • Welcome. Please revise your post title to ask a clear, specific question. Take the tour to learn how this site works.
    – isherwood
    Apr 25 at 14:03
  • Your question is still quite broad. It's not reasonable to ask for a complete diagram. I suggest a read through a basic house wiring book so you're safe. It will give you the planning tools you need.
    – isherwood
    Apr 25 at 15:20
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    What does the 12/3 connect to at the "distribution box" - are you planning a MWBC, or what? Far too vague.
    – Ecnerwal
    Apr 25 at 15:30
  • also i havent connected it anywhere in the power box until i figure out how ots suppose to be done , easier here then getting a book nearest big box is over 40 miles figured i would ask for help , im a visual person if it was drawn up i can wire it
    – V P
    Apr 25 at 15:55
  • Normal people buy their lumber and electrical somewhere. There is probably a family owned lumberyard and hardware store right in town and they're probably much better than a cruddy big box store. For instance my local lumberyard sells wire by-the-foot. Much more civilized! And Amazon sells almost all books in e-form, read them on your PC, tablet or phone with the Kindle app. It sounds like you are just making excuses. Apr 25 at 18:33

1 Answer 1


Whether you know it or not, what you're installing is commonly known as a MWBC (multi-wire branch circuit). Connect one of the hots to the GFCI outlet and then connect the other outlets downstream from that, connected to the "load" side of the GFCI outlet. Then, using the other hot, connect the fan and lights. Sometimes, GFCI's don't always play well on a MWBC. Also, when connecting the hots to the breakers in the main panel, they must be handle tied to be code compliant. EDIT: The neutrals are all connected together and the grounds are connected as well. But like @isherwood said, it's a good idea to buy a basic home wiring book from a big box store (like HD or Lowes) and get to know the ins and outs of wiring.

  • 1
    Library is also an option for the book(s).
    – Ecnerwal
    Apr 25 at 15:42
  • thats exactly what i was thinking but what confuses me is i want the lights 3 includes the fan light on 1 switch and the fan itself on another switch , thats where i get confused
    – V P
    Apr 25 at 15:52
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    If I understand your comment correctly, you want the fan and lights switched separately. That's not a problem, just supply power to both switches (pig tails is best practice). If the fan unit also has a light, you'll need to run 12/3 to it, one leg for the light and the other for the fan. 12/3 is hard to work with, esp. for lighting, IMHO. The already installed 12/3 is a sunk cost, but you might consider treating it as a 12/2 for just the outlets, or keep it as a MWBC, but then you'll need 2 GFCI outlets for each leg. Then run 14/2 for the fan and lights from the main panel. Apr 25 at 16:10
  • Given the macerator toilet and the 20A countertop, an MWBC feed for the room is likely good - but I would also lean heavily towards a separate run of 14/2 from a 15A breaker for the lights and fan separate from those two, unless the macerator is quite low-powered.
    – Ecnerwal
    Apr 25 at 16:49
  • @Ecnerwal I think we are in good agreement on that. I get too subtle at times, but I'm just a polite guy! 14/2 for lights and fan separate from outlets is always best practice. That way, if you trip a breaker for an outlet, you're not left in the dark. OK, no more Mr. nice guy: RUN A 14/2 FOR YOUR LIGHTING / FAN CIRCUITS, AND PROPERLY DIVIDE THE 12/3 INTO A MWBC PROTECTED BY 2 GFCI OUTLETS, ONE FOR EACH HOT. .....Ok, that's considered yelling in all caps, but it was fun...hopefully no-one takes any offense! Take care and wire-on. Apr 25 at 22:05

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