S
sheff paul
The installation of terrier valves in every radiator is a good idea specially in the bedrooms, but that will not provide boiler interlock. In that case radiators will be shut but boiler will carry on working for as long as the programmer is on through the by pass. The by pass should be installed before the motorised valves because that will open when motorised valves close for boiler overrun in order to cool down.
I for one would be using a room stat down stairs,and upstairs programmable TRV's,yes I know the boiler shuts off with the room stat,but most building inspectors wouldn't have a clue anyway,but I can guarantee the heat exchanger on the combi will last far longer,and will run quieter,dont mind multiple zones on unvented, system boiler installations,but on a standard combi installation its hard to be competitive,and up our way I know that over a 100 fits a week are going in on local authority houses all unzoned