Even with the central heating turned off the radiators come on with the hot water. I assume this must be an electrics problem. Is the main PCB faulty. Any advice gratefully received.

Alan Matthews, October 2006

i presume you have a open vent sysyem (header/expansiontank ect) almost certainly your motorised valve which controls the route of flow to c/h , h'w or both is not operating properly and there fore allowing flow around all pipework, rather than shutting the entry to the c/h when in hot water mode. you can check by alternating h/w -c/h call up and seeing if the valve moves to its appropiate position.

Desman, October 2006