I HAVE A RAVENHEAT BOILER WHICH THE HEATING I.E. RADIATORS WORKS FINE, BUT THE WATER WILL NOT HEAT UP UNLESS THE HEATING IS ON (WHICH IS UNCOMFORTABLE ESPECIALLLY IN JUNE) IV HAD A PLUMBER M8 OF MINE TO LOOK AT IT AND HE THINKS ITS THE ONE OF THE RELAYS WHICH LOOKS LIKE IT HAS BURNT OUT BUT HE...