Basic Evohome queston

[NickNightingale]

I would like to use an Evohome to replace the control on my Y-plan system (non-condensing boiler and vented HW). I cannot afford to replace all the thermostats with HR92 in one go but I would like to do this for one of the bedrooms. If the Evohome is wired with the two BDR91 relays (one from the HW kit) controlling the Y valve and the boiler activated by the Y valve switch as per the diagram on page 47 (using the control unit as the sensor), can I then add a new zone for the bedroom with the HR92s?

[Dan_Robinson]

And any rads without the heads will get hot as well.

[NickNightingale]

Thanks very much for your reply. I am hoping that all the rads without the HR92s should be controlled from the sensor in the controller. I can see that there would be no way to have the bedroom hot without the rest of the rads getting hot, but for now I want to be able to lower the bedroom temperature WRT the rest of the house during the day. My SO works from home and it would be good to be able to keep her area warm without heating the bedrooms.

In the longer term when I can get HR92s on everything would you still end up with the standard Y plan wiring or is there a better way maybe to set the Y valve and have the boiler on a separate BDR91?