I have just moved to a house where it has an old boiler, it is Worcester, heatslave highflow type. When I tried to switch it on from the mains, after lighting the pilot, I could hear a lot of rattling nose from the pump as well as the timer. Consequently, I managed to install, new pump, new two port valve, and new timer. It is now working perfectly, but pump seems to be always working, whether the CH on or off or the DWH on or off. In my opinion the pump should come on when either the CH or DHW is on demand, any other time it should not be running, am I right in assuming this? Is there any relay stuck on the PCB, can someone advice of where I can get a manual for it, any input or advice from anyone would be highly appreciated.

 

Id say check the tstat first. This should control the pump and the zone valves.

 

Ed
which tstat and where it is located?