Connecting a Tado Smart system where there has never been a room-mate.
I am replacing a Drayton Lifestyle 112 with a Tado Smart system including DHW. It controls a Vaillent Ecotec Plus 637 system boiler but there has never been a roomstat connected. I have everything else up and running and am happy with all the other wiring but, I am not clear as to how the thermostat connects. The boiler has two places for a thermostat, one for a smart connector and one for a 240v thermostat. I'm not sure about which one to use. I am away to look at the wiring diagrams and am sure I will eventually work it out but an answer for someone who has done it successfully before would be welcome. My heating engineer friend who was serving the boiler for winter gets a sparky to do this work and as an electrical engineer I should cope with it too!!