worcester/bosch 24cdi pressure keeps rising

[gas_man_gaz]

i wouldn't turn off the isolation valves or use the prv to drain - no need! turn the boiler off, open the drain off like has been said and pump up the exspansion vessel to around 0.7 - 1bar. wen refilling check the aav is open, bleed the rads and fill to just over 1bar

 

[h4gg13]

As Gaz has said DO NOT close and re-open flow and return valves as they will leak once they have pressure on them again. To replace these valves when leaking is a royal pain in the butt as the the complete hydraulic section has to be removed to do so.