I currently have a set of lights controlled by two switches. I believe they are both three way switches, I know one of them is.

I am trying to install a timer while keeping the three way switch function. The timer has three wires: Load, Line and Neutral. Model RPLS730B. I need help on how to wire this.

I do not know how the setup is currently wired as far as what each wire does. From observation it is wired as shown below.

Switch 1:


 Black               Red

 Whites are tied together

Switch 2:

 Red                 Black


Additionally if someone could explain the current setup and the circuit of each wire that would be great. I do not understand how they are connecting to the lights.

:edit: The traveler on switch one is Black and the traveler on switch two is White.

  • An easy way to tell if it is a three way switch is to identify the Common screw (usually black) and two Traveller screws (usually gold). When flipping a three-way switch, power is switched between the two travelers. Are you absolutely sure that the white wire on switch 2 is not tied together with the other white wire coming into the box? Is the white wire on switch 2 marked at all? Commented Nov 28, 2012 at 12:27
  • If switch 2 were a two way switch then it is wired incorrectly. I wonder where the neutral for the luminaire is going? Is the white wire on switch two connected to the ground screw? If you could provide pictures it would be helpful. Commented Nov 28, 2012 at 12:30
  • 2
    Related: diy.stackexchange.com/questions/12317/… Smart switches need a dedicated neutral to operate internal electronics. Commented Nov 28, 2012 at 12:38
  • 4
    Here is my guess at the current wiring, is this correct?
    – Tester101
    Commented Nov 28, 2012 at 13:14
  • 3
    Depending on what you want, the cost may vary. To have the switch OR the timer turn on the load is cheap and easy -- but it means for example, if you turn on the switch, it permanently overrides the timer. If you want to be able to remotely turn off the light when the timer turns it on, or have the timer turn it off if you've remotely turned it on, you'll need a real 3-way timer. A quick look around shows Leviton makes one that has a special "coordinating remote switch", Smarthome has some stuff that can be linked, and there are others that say they're "3 way" but I can't find manuals.
    – gregmac
    Commented Nov 28, 2012 at 15:54

3 Answers 3


Thank you all for the help.

I ended up purchasing an Intermatic ST01 which is intended for three way installations. They even have a youtube video that makes the install foolproof. It also does not require a neutral wire, a wire I do not have.


If you have more than two screws on a switch it's probably a 3 way. The other option would be a 120v/240v switch or something like that for a motor load possibly. If you have a black screw where the red wire is tied to on each switch, it's a 3 way. Yours are probably both 3 ways. They would not operate if they weren't. Anyway here are a few variations on how to wire that up:


great and easy to follow!

Forgot to mention the timer has to be a 3 way timer as well. From the pdf you linked it didn't look like it was unless I missed something. I know a lot of those are both single or 3 way depending on how you want to use it.

  • Mike's timer is not 3 way. His only options are to either wire the switches in series or parallel. I haven't seen electronic switches that are true 3-way. They typically provide a 3-way like function only if they are located at the power side of the travelers. They do not work properly on the luminaire side unless there is unswitched power available.
    – bcworkz
    Commented Nov 28, 2012 at 21:37

It involves rewiring but you could install two single way switches in parallel. I just went through this to do a in line bathroom fan controlled at two bathrooms:

enter image description here

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. Commented Jan 17, 2020 at 17:52

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