I managed to luck onto the solution myself, If you are interested when I refilled the system after partial drain when fitting a new radiator I put in some cleaning fluid. What I think happened this product cleaned the HW heat exchanger and made it more efficient. The resultant efficency caused...
I have a worcester 240 that has a problem with the hot water.
CH runs ok no problems. When I turn on a hot water tap/shower runs ok for about 5-8 mins then makes a noise like an plane flying overhead and the unit trips.
I have flushed the water-water heat exchanger and checked the operation of...