Speadie - I see that you seem to be the resident expert here. I have a battery operated thermostat that controls AC in the summer and then via manual switch to heat, controls the boiler/radiant floor heating in winter. Wires to thermostat are Rh and W then Y, G, Rc. There is an abandoned blue wire at the thermostat that runs to the AC unit. No control board. I tried connecting the Blue wire at the AC unit to the C from the transformer and then to the Wyze (Rh to Rh, W to W, Rc to Rc, Y to Y , G to G then C to C) - the 3 amp fuse from the transformer positive blew. I checked the resistance between R and C wires to thermostat and it tests infinite. I then tried the C wire adapter and the fuse also blew. Any suggestions?
hmm. do you have any pictures? specifically a picture of the wiring at the furnace and the wiring at the air conditioner.
Wyze should hire speadie as a consultant. 
The blue wire in the AC unit goes to the common side / ground of the transformer and the blue wire from the thermostat picture runs to the AC unit. That’s the one that I connected to the blue from the transformer.
Red and White to the heat / boiler runs to the radiant heat controller box.
I don’t see that blue thermostat wire in any of the bundles in the A/C unit picture. do you have a picture of it?
So far this is all I see… where does the second wire set that goes to C, Y, and X go?
In the first picture from the stat to the AC handler = W to Y; R to R; G to G; blue is disconnected outside the unit
Then from the handler to the outside unit Yellow-black to red; blue to white; green not used
First, I would try hooking the thermostat up at this location, to verify that you have a working thermostat and eliminate the wiring as any sort of fault.
The two red/blue Y wires are a float switch that turns off the compressor if you have a clogged condensate line, you can ignore them for now.
The thermostat only needs Rc and C connected to power up, try that first, and if it still blows the fuse, you have a faulty thermostat.
If the thermostat powers up here, then disconnect it, reconnect the wire nuts and connect the blue wire here to the C wire nut in the picture.
If you have a multimeter, check the voltage at the thermostat. The blue wire should now have around 24-29 VAC between it and the red Rc wire.
If you hook up the thermostat at the thermostat location after doing these tests and verifying the voltage, it should work, and not blow the fuse - if it does, then the wires likely have bad insulation which is shorting out when you push the wires back into the wall after mounting the thermostat backplate.
Ok Speadie. Step by step and the thermostat powered up at the wall. I left the boiler disconnected and just out of curiosity checked the voltage between Rh and white and it too has 24v
This is the manifold for the rooms where the thermostat controls.
Have not connected the boiler as I am sure that it will blow the fuse on the AC.
Any guidance?
I disconnected the Wyze for now
And one more observation. Rh and white both had insulation missing at the thermostat/wall and were likely touching - who knows for how long. I was able to cut back the wire (enough pulled out of wall) and now have good insulation
Hmm. Rh and white has a voltage difference? You may need an isolation relay to isolate that part of the circuit from the AC system. Do you know where RH and W come out in the boiler room? A 24V fan relay should be able to keep the boiler and the AC systems separate, so the wyze would only operate the relay and the relay would operate the boiler.