My ancient cast iron boiler is being replaced with a shiny new Worcester Greenstar 24Ri. It will drive an S-Plan system with separate valves for Heating and Hot water. My CORGI Installer has correctly advised me that an automatic bypass valve should be fitted to the system. I understand that this bypass valve together with the in-built pump overrun allows boiler hot water to continue to be be circulated and thus cooled when both Hot Water & Heating valves are closed after the Demand signal is removed. My question is where does the heat get dissipated as it is no longer diverted to either the radiators or the hot water coil ? I assume it just circulates in the pipework between the boiler the and pump ? It occurs to me that it would be better to perhaps usefully 'dump' this excess heat into the hot water coil ? A simple bit of 'electronics' could detect pump overun, open the HW valve and also remove the Demand signal until the boiler has cooled sufficiently. Does anyone see any 'snags' in this scheme ? It will save me the cost and labour of installing a bypass valve and more importantly use this precious heat.