My sealed system loses pressure when I run the hot water. When boiler cuts in the system builds up pressure again, but not upto full pressure 1.0 bar. When heating is on the pressure builds upto 2.0bar which I think is normal. Cannot see any leaks, could it be a faulty diverter valve.

John, October 2011

in combi pressure filling loop, than pressure guage and pressure expenssion tank and pressure relif valve if one of is at faulty that does when heating on bar goes up when cool goes down in your case if on leak out side from relif valve than look like expenssion tank need recharge

ltd, October 2011