Ferroli Modena 80E not playing!

[peteisfishing]

Hi all, just been round to take a butchers at their boiler, working fine with DHW but when demanding CH the boiler fires, pressure rises to around 2.5 Bar then the boiler shuts down and the pressure drops quite quickly back down to 1.2 bar.
The needle on the pressure clock is very 'Jerky'
It has been working fine for the last 5 years and now this. I am keen to get it sorted as they have two young kids

My initial thoughts are maybe the expansion vessel pressure low or a knackered pressure relief valve?
Any thoughts?

Cheers

 

[wnjswozo]

expansion vessel ,test it you will soon find out

 

[RoryD]

Could b a number of reasons. Check the PRV isn't discharging. Either way it may b necessary to put about 0,75 - 1.0 bar of air in via footpump. Isolate chb, Blow boiler off and keep PRV open. Attach footpump to schrader valve and pump up to the above pressures. Shut off valve, refill and pray it doesn't pass. I usually run water thru with open to clean seat.

 

[peteisfishing]

Typical, went round today to investigate further...................and the thing is working fine!!!!!!

we will see how long for though, i have suggested if it goes again i will flush the system to eliminate sludge clogging the pump

What do you think?

cheers for the help