The thermostats will not work without a C-wire. Our control panel had to upgraded in order to make the connections. It was much more complex and expensive than I expected.
I like the system overall. I bought one additional sensor and it works, but I wish I knew that it was motion activated. What I wanted was to be able to program the system to read only the sensor instead of the thermostat. The reason for this is because I have a fireplace that skews the temperature in that room to a temperature that is 3-4 degrees higher than what the thermostat is set at. So I wanted the sensor to help by being far enough away from the thermostat to even out the temperature in the house. As I said it does work, but only when motion is present every so often. That is the only reason I didn’t give it 5 stars.
We had a professional switch out our old thermostat..after watching him it was in approx 10 mins start to finish. The only con is the unit remains lit and there is no mode to adjust, so room is darker at night. Otherwise 5 star.
Like the thermostat however I wish there was a more options to lower the backlight at night. The device is in the bedroom and while you can lower the backlight to 10%, its still too bright. The next option is to turn it off completely. I would give it 5 stars if you could lower the backlight by 1% increments rather than 10%