I currently have a 3 way light switch in my stairwell. One at the bottom and one at the top of the stairs. I recently added a light fixture to the bottom of the stairs but need some help wiring it up. I have been rewiring the whole house but the 3 ways a bit confusing to me. Power comes in from the light fixture at the top of the stairs. Here is a diagram of what I have and what I am trying to do. Any help would be great.
Smart switch; change one cable
The cable from the existing lamp to the nearer switch (upstairs?)... you need to change that to a /3 cable (red white black).
You can extend the cable to your new lamp from any switch box. When you do, use colored tape to re-tag the black wire as a red wire.
Now we're going to fit smart switches that allow wireless connection of remotes. These smart switches cannot require a wire for comms between them, as we lack any spare wires.
Now we're going to change the color codes. As it happens, the existing color codes will suffice in all locations:
- black = always-hot
- white = neutral
- red = switched-hot
Your master smartswitch attaches to black, white and red.
Your remote smartswitch attaches to black and white only.
Your original lamp connects to red and white.
Your new lamp attaches to red and white in the box nearest it.
Please clarify: is there an existing light fixture which is working properly with the existing switches? If there is, you need to run 2-wire from it to the new fixture and from the new fixture to the existing box on the left in your diagram. Wire both light fixtures in parallel, i.e. the white return to mains power goes to both, and the black output of the left-hand switch goes to the hot side of both.
This does mean you can't "cheat" as in the diagram which uses a single 2-wire cable for both the mains Hot input and the returning Hot to the light fixtures.