 andytw, 00 Apr 0000 #00 Sponsored Links oilhead Joined: 00 Nov 0000 Messages: 0,000 Thanks Received: 000 Location: Shropshire Country: Oops! I only looked at the felt tip writing on it. Seeing that however, makes me wonder whether the problem is confined to the room stat which OP suggests is programmable. If the installer has taken a direct live feed to it instead of across the normal thermostat connections, then this may override the valve when not required. Twin burner cookers, oil or gas, often pose problems to technicians who only work on boilers and do not follow the wiring diagrams because 'they know it all'. As an example, fitting a frost stat to a Rayburn, rather than bridging the heating circuit, you feed into the Hot Water Off terminal on the junction block. oilhead, 00 Apr 0000 #00 andytw Joined: 0 Feb 0000 Messages: 000 Thanks Received: 00 Location: Somerset Country: 