Indirect water cylinder

[fixitflav]

I actually think that programmer may be fine - once the hot water is satisfied, then the cylinder stat switches over and sends the SL to T6, that then connects to the CH common, the reason for the double connection - from HW S (off) to the CH - will be for when the HW isn't being called for by the programmer, it then sends the HW off SL to the CH.

Can't agree with that. With the type he's got, when CH is called on the programmer (and the elusive roomstat calls), the diverter valve goes to CH, even if HW is called. That's not PDHW. In that situation, the boiler (I think) goes to HW temperature, so no W comp.
That's my take on it anyway.

 

[fixitflav]

Can't agree with that. With the type he's got, when CH is called on the programmer (and the elusive roomstat calls), the diverter valve goes to CH, even if HW is called. That's not PDHW. In that situation, the boiler (I think) goes to HW temperature, so no W comp.
That's my take on it anyway.

I found a Potterton EP2 programmer which is suitable, attached (couldn't rotate the image). The link L to 5 removed from L and connected to 1