I've got a problem with my combi boiler, Radiant RS24 model, installed in 1999.
Basically I noticed the pressure was high, over 3 bar so I dropped the pressure down to just over 1bar, within a couple of days it was over 3 bar again.
I drained it back down to 1 bar, turned on the central heating and it immediately jumped up half a bar.
I checked the topup loop, which appears to be fine but I then noticed that when Iturn on hot water the pressure drops down half a bar again.
Any idea's (expansion vessel maybe?)