i have lately been having a few issues with my boiler, when i have the heating on so that the temperature dial is at about half way, the pressure dial after a short time goes up over the 2.5 bar red line to somtimes 3-3.5. to relieve this i have to then bleed one of the radiators to lower the pressure. this works fine except when the heating then goes off the pressure goes way down to sometimes almost to the .5 mark red line, when i the turn the hot water tap on it goes down even further. this is really starting to concern me, can someone help?
inside of your boiler you have an expansion vessel, when your heating is on the water in your system expands due to the heat, and the expansion is what it expands into. It just sounds like your expansion vessel needs to be reinflated!