So I went to swap out some switches in my hallway today and I have spent the past 4 hours reading how other people have done it and test all sorts of combinations.

The setup is this - There is a three way with one switch in one box and then there is the other box that has the two way and the other side of the three way.


In the One switch box there are two white, two black, and a red. No grounds in either box, old apartment.

In the other I have attached a photo to better explain it. The photo shows what it looked like before I took out the normal two way switch. The orange circles are the different places it comes in from the wall. I have noticed if I undo either of the white or reds that are together I lose power to everything else that is controlled by that breaker.

 

Two way switch is a term for three way switch used in Great Britain. Just so we are clear do you mean a single location switch (SPST). That is a switch used when a device is only controlled from a single location. The switch on the right of your diagram is a single location switch (AKA SPST).

In a 3-way switch set up the wire colors are optional at the discretion of the installer so actual colors aren't all that helpful. What is important is which wire is connected to the common (odd colored screw, usually dark gray on newer switches).

 

The one in the photo is of the double gang box that I am adding one of the switches for the three way switch.

Wires that aren't attached to anything are what I have to connect to the simple side of the three way Z wave switch. But when I connect the dummy side of the three way switch nothing happens. I have learned through trial and error if I connect the black to white to the top of the switch that I can make a wonderful blinking strobe light.

This is the unit I have:

Amazon.com: GE 45614 Z-Wave Wireless Lighting Control 3-Way Switch Kit: Home Improvement

I am in the US not UK

 

I know. That's why using a UK term was confusing. I'm sure you meant a single location switch but two way switch and three way switch mean the same thing.

Commons are key to this but you have yet to tell us which wires go to the common. Wire color doesn't tell us that for sure.

 

Well I've done what I believe is literally every combination of wires and I've tested different signal wires and I've done continuity tests. What I've realized is the wire colors in my walls don't mean what they are. I've got to start back at square one tomorrow and check which fixtures are plugged into which wires. They've piggy backed lots of connections on each other and I'm getting really strange results when I wire things with even normal lights.

This looks like a bigger project than I imagined.

 

Ray, does the fact that the new switches are "wireless" mean that it cannot be a simple direct swap?

dcantato, Did the three-ways work correctly before? Did the SPST correctly control a different light?

Cannot be certain without seeing the wiring for the light that the three-way is supposed to control, but I believe correct wiring would be (switch 1 on left);
1 White to all whites
1 Black to breaker box
1 Red to 2 Red

2 White to all whites
2 Black(a) to breaker box
2 Black(b) to light
2 Red to 1 Red

Need to make sure that you have 2 Black(a) and 2 Black(b) connected to the correct screws on the switch.

EDIT:
I'd have to draw it on paper, but I think the above would work if breaker goes directly into three-way(2). I'm pretty sure that someone could make it work by having power go to the light first, but that would involve messing with how whites and reds connect. Hopefully your light box has only Black and White (and ground from a flexible tube) so that we don't need to figure out other messing things.

 

Just a quick pass thru here.

In your picture the two wire coming into that box is a "feed in."
The three wire carries the hot out on black and a switched hot on red.
The whites are the neutrals and are just spliced thru.

I'm guessing the other three wire goes to a 3 way switch.
If that guess is correct.....and that left hand wire connects to a 3 way switch......then the Z wave switch can't go there as that would appear to be the end of the three way circuit. It would need to go at the other end.