When I turn off my central heating and have turned all the controls off why does the heating still stay on when I open the hot water tap?

Valliant Boiler
TurboMax VUW GB 242-5

Richard, December 2009

I have a Drayton Wireless Digistat which says the heating is on but the boiler is not kicking in - wireless receiver shows green light and signal being received.
Boiler is Valliant EcoTec Plus and hot water is fine.
What is wrong? I have changed the batteries in the Digistat but still no luck.

Gillian, January 2010

dhw flow switch is probably sticking

Ian, December 2009