I have a 220V electric baseboard heating system which is controlled by a 24 VAC 2 wire thermostat (RH, W). There is a 220V to 24VAC relay in the circuit from the thermostat to the heating system.
I plan to replace the thermostat with a WiFi enabled smart thermostat so I can control it remotely. The Smart thermostat (Emerson Sensi) needs a C wire (return ?) so the thermostat can be powered.
My choices are 1. Use an external 110V to 24VAC adapter from an outlet to power the thermostat (connect to C and R terminals on the thermostat) 2. Replace the existing relay with a transformer that has a common wire and pull a 3 wire thermostat cable through the floor & wall.
I plan to do option 1 now as it's zero risk in the middle of winter and follow up with Option 2 in the summer. I'm not sure which transformer I need to get for the 3 wire (RH, W, C) application. Any ideas ?
Also, the current thermostat has a backlight feature operated by a button to light up the dial - so, it is able to use the power from the RH wire to close the circuit. Can I simply jump the RH connector to the C connector in the thermostat ? I have a feeling this will cause a short.