My old but extremely reliable system is a bit inefficient, because the HW has to be on if the CH is on. I want to add a second 2 port valve on the HW primaries, and a cyl stat to make it S-Plan.
As the 2 port valves have microswitches that only turn pump and boiler on when they are open, and the Concord WRS boiler doesn't have an overrun, do I need to put a bypass on the system? Also, can I keep my Potterton EP3002 programmer if I change to S-Plan?
(Feed and vent pipes not shown in diagram)