Enerwave ZWN-RSM2 3-way switch

I am installing Enerwave ZWN-RSM2 in a typical upstair/downstairs setup. Can anyone tell me if Enerwave ZW3K is required or can I just use my old 3 way switch that is already there?

I believe that you are asking if it can be used in what is called a 3-way circuit. If so, then the answer is yes. If you look at the right side of page one in the ZWN-RSM2 Manual you will see a wiring diagram for two 3-way circuits.

You’ll need to reconfigure your wires a little bit, but its perfectly possible to use your existing 3-way switches(also 4-way or more) with this relay.

I used this relay to make a 3 way without needing to run a 4th traveler. Use both inputs, one output and a luup program.