installing smart thermostat on steam boiler

JoeyPipeWrench

I have a steam boiler that I would like to install a smart thermostat on. I have three wires behind my current thermostat. Only two wires are connected to it, those two wires being W1 and R. I have a spare wire which I would like to use as a common. What is the best way to make that spare wire into a 24v common? I would assume I could just put in a new 24v transformer near the boiler in the basement, but I’ve been led to believe it won’t work that way. Any help would be great!

sputnik99

My hot water boiler only had two wires and I replaced the wiring with 5 wire thermostat wiring. I plugged the 24v transformer into the boiler room and connected it to a couple of spare wires to the Ecobee thermostat on the first floor. Been working fine for 5 years now. I don't remember the wiring scheme, but your wifi thermostat should have a guide.

Jamie Hall

Contrary to what someone may have mislead you, the best way to hook up your new thermostat is to use a new transformer and a relay. It's not hard. Common from the transformer to common on the thermostat. Hot on the thermostat to red on the thermostat. White on the thermostat to one terminal for the coil on the relay. A wire from the other relay coil terminal back to common on the transformer. The normally open dry contacts on the relay to the burner control on the boiler (where the old thermostat was connected).