Boiler on the blink, help needed :)

[evesdad]

To check if expansion vessel needs re-pressurising top boiler up to just over one bar when the system is cold. Put the heating on and watch the pressure gauge..if the pressure rises over 3bar then the vessel is flat. Pressure relief valves start letting water out of the system at 3 bar, so when the system cools down again water has leaked out of the system so the pressure goes down to zero. The pressure relief pipe should goes to outside so you don't notice any leaks. On your boiler the pressure relief pipe is the one to the left hand side closest to the front of the boiler see if you can find where that goes to and if it has been dripping. Expansion vessels can usually be pumped back up but prv may need replacing.