My central heating/hot water system has become very unpredictable and temperamental. I have a new baxi condensing boiler, motorised pump,hot water tank and I presume an open vented system. All the radiators have a habit of heating up when the water should be heating up for the hot water tank. This doesn`t happen all the time but I`ve noticed that it tends to happen after the central heating has been on. I have set my timer so that the central heating and water heating functions are at different times of the day and not on together but the problem still occurs. The timer is set to fire the boiler up for hot water first thing in the morning but quite often all that happens is that the rads get really hot throughout the house.I can sometimes correct this by switching the timer off and on again and this seems to reset it until the next time.Please help!!