I have a 6 year old worcester 28i junior boiler and the overflow started. I checked the the boiler and both the CH & HW are working OK but the pressure is above 3.5 hence the overflow. Can you suggest what the cause might be and a cure for it please?

cliff, October 2010

when did you last check the pressure in the expansion vessel ? you do this test with no water pressure in the system inflate the vessel with a car foot pump to 1 bar max pressure, then repressurise system on the water side using the filler loop to 1 to 1.5 bar cold disconnect one end of the filler loop.

wirecutterman, October 2010