I have an old Valliant Combi VCW Sine 18 T3 boiler and would like to change the old mechanical room thermostat. The manual states the stat model as a vrt378.
I would love to upgrade to a modern digital stat if possible.
I have checked the wiring of the old stat and there are 3 wires - yellow, red & blue. There is no earth wire that i can see so am really stuck as to what is a direct replacement. anyone any ideas?