I have a Baxi Combi 80Eco boiler. It is firing up every 10 seconds or so, stays in for a couple of seconds, goes out and then repeats. This happens when the control is set to DHW/CH and the heaters are warmed up and the hot water tap not turned on and it also happens when the control is set just to DHW alone without any taps being turned on at all. The only time it doesn't fire up is when the control is set to off. Any help would be appreciated.