DIY Doctor UK DIY Forums

Hi, need help with the position of the motorised valve which will be connected to the cylinder stat. Boiler supplies heat for rads and hot water which is fine but want to stop the water from overheating hence the stat.
I can access the pipework at A and B but don't know which is the best side to fit it on or even if it makes any difference.
Any help much appreciated, thanks.

Clearly A the three port valve will default to domestic hot water, half way for both and all the way for central heating only.

If TRV's are fitted then also needs by-pass valve.

In theory with Y Plan the micro switches stop the boiler running without the valve being open, and since default is domestic hot water unlikely to be a problem. Using S plan however a faulty micro switch can burn out pump if by-pass valve in the wrong place.