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We are rewiring the entire old house. Completely removed the bathroom wall and rebuilt it to expand the size of the bathroom and remodeled. The new L-shaped wall will have 3 separate light switches on three different walls (west wall inside bathroom, east wall opposite in hallway and south wall of office outside corner of L) leading wire to three different low demand LED light fixtures in the different ceiling places (inside bathroom, opposite in hallway and outlet for lit display cabinet on south wall).

The entire house is being rewired from underneath with metal conduit through drilled framing inside new walls to gang boxes or junction boxes (depending upon application), then Romex upward. Junction box for this application to be inside wall and attached to framing 2 x 4’s (the entire area is about 4 feet wide). Have looked for a diagram on line to connect wiring in junction box and then to each switch independently. Wanting to be safe. Using 14/2 Romex.

Currently running my entire home on a 1600 W generator with construction grade power cords everywhere (non-electric lp wall furnace, lp kitchen range, lp water heater and wood burning stove for most heat - no electrical demand on all that). Have already ripped out walls and placed boxes and receptacles, drilled into floor framing and installed individual receptacles with metal conduit going underneath house (new drywall installed) waiting to be connected when better breaker panel is installed at some point in the future. This is my off-grid dream. Have done all sorts of massive work alone. I’m a 60 year old Grandma. No debt. Showing my grandkids how to live an independent self-reliant lifestyle. Just really need to feel secure about the junction box wiring from the source up through the floor to the routing of hot, neutral and ground wire nutted in the junction box.

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    There is a lot of info in a wall of text. Please edit to break it up into some paragraphs to make it more readable. What I think you're asking is how to wire a switch in a junction box. Whether this is new or old construction, wiring with cable or conduit, incandescent or LED, the wiring of a switch is the wiring of a switch. While we're proud of you for doing it DIY, there's a lot of material that's irrelevant to the question and makes it hard to suss out exactly what you're asking. Please be very specific about what your question actually is by highlighting so we can easily find it.
    – FreeMan
    Jan 4, 2023 at 12:41

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Based on all the work you have already done, this should be an easy thing to do!

There are really only two keys:

  • Junction boxes must always remain accessible - not hidden inside a wall.
  • Box Fill

Since most people don't want a blank plate on the wall you have two options:

  • Install a junction box underneath with the metal conduit and run three separate NM cables to the three switch boxes. This has the advantage of a smaller box (though at the same time, a large box could be used here and nobody would know or care).
  • Use one of the switch boxes as a junction box for the feed to the other two switches. This is actually very common and has the advantage of using less wire based on your description.

Box fill gets complicated. It includes the number and size of wires, the number, size and type of devices and some other factors. The easiest thing to do is use an online box fill calculator such as this one.

  • Separate junction box - 2 wires coming in, 3 x 14/2 going out. According to the linked calculator, if I did this right, that is 18 cubic inches, and will fit in anything from a deep single gang box on up. I would probably use something like a 4" square, 1.5" deep box and have room to spare for adding a future connection or two if needed.
  • Switch box - 2 wires coming in, 3 x 14/2 going out (1 to fixture, 2 to other switches), 1 switch. 22 cubic inches. 4-11/16" square, 1.25" or deeper. Or 4" square, 2.125" or deeper. You can use a 4" or 4-11/16" box with a single gang mud ring and nobody but you will know the box is any bigger than a standard single-gang box.

The other option is to use low-voltage LED lighting. That can save energy overall, which matters more when you are off-grid than on-grid. However, that really gets complicated because the low-voltage wiring needs to be kept separate from the 120V wiring. With the incredibly efficiency of modern 120V LEDs, I would stick with the existing plan. However, that means you don't get any advantages from "just some low-power LED lights" - everything has to be wired to normal specs - minimum 14 AWG wiring, box fill, grounds, etc.

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