baxi 105e, - only hot water is selected however sometimes the boiler fires up and the rads (ch) comes on. Not ideal in the summer. There is no indication on the boiler that the CH is on.
Any ideas ??

ade, July 2009

The o-rings in the 3 port diverter valve will be passing allowing the water that should remain in the boiler for the hot water to leak into the heating system. It may fire up by itself if you have the model with the water pre-heat, you could turn the pre-heat dial right down to fix temporarily.

Ian, July 2009