Pressure problems

[mikesull]

my ferroli modena 102, started discharging i believe that it was my expansion vessel. i have now installed an external expansion vessel which was working ok until i found a lot of air in one radiator i have since vented the rad and re-pressurised but now the system is getting up to 4 bar and discharging again.

Any ideas

 

[Boilerman2]

Check to see if the Filling loop is letting by when closed, disconnect the hose to prove, if pressure rises with hose dissed suspect HW Plate Heat Exchanger (primary/secondary water mixing)

 

[Newcastle88]

what size expansion vessel did you fit? did you fit it on the return? and what pressure is the external expansion vessel charged too?