I have a turbomax 828e valianlt boiler which supplies hot water to the taps and the central heating. However, my boiler now starts to heat the radiators without demand. I still get hot water but why is it heating up the radiators even when we have not turned the heating on?
It does this randomly and we have no idea as to when it will go on so we keep our boiler switched off unless we need it.
Can anyone help? I spoke to boiler guy who said that the timer may be busted - he is visiting this Saturday.

David Henri, May 2007

Two things spring to mind. The boiler has an electrically operated diverter valve which goes between the heating and hot water positions. It also has the facility to pre-heat the hot water.
If the diverter valve is sticking in the heating position intermittently and you also have the controls set for hot water pre-heat, the heat would be able to get to the radiators when the boiler fires up to pre-heat the hot water even when there is no demand for central heating.
To test for this if you shut off the hot water pre-heat function the fault should diminish although it may still happen when you run the hot water taps.... does that make sense??? It's worth a try.

T.h.s, May 2007