Radiators red hot,boiler set to Hot Water only. Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[Grey Fox]

Hi.I have a Saunier Duval Combi boiler (condenser)hot water & central heating system which now defaults to central heating on(max temp!)when the boiler is switched on and Hot Water selected.The system was installed in 2003 and is regularly serviced.I have tried a reset but no luck.I have turned off all rads and just switch boiler on when i need h/w then switch off again,any ideas what could be at fault?many thanks.

[screech]

diverter valve will either be passing or jammed in heating mode.

can also be other causes but that's the most likely