Our hotwater stopped working , however the Central heating still works. When you switch the hot water to 'on' or on 'timed' this knocks the central heating off. When hotwater is at 'off' the central heating is fine.Changed timer as had a old Switchmaster to a drayton tempus but this has not sorted the problem. Curretly using the electric to heat the water but elec bill will be high so need to get this sorted, any ideas what this could be?