i have a modena 80e ferroli boiler that is ok when the heating is on and then when it is off loses all its pressure the automatic air vent was leaking so it was changed and its still happening . i have had e new expansion vessel and pr valve to no joy .

there is no obvious leaks - any ideas?

kirstynurse, February 2009

check pressure vessel is sound with right air pressure
see if gauge is going up when heating is on may be discharge to P valve and gauge down when system cold. than p. vessel not correctly size i gess

Mr K, February 2009