HI All, i have an LG 14kw ashp powering hot water and central heating in a 5/6 bedroom house approx 350sqm, i have not issues with the hot water side of things, this works perfectly however, the central heating side gives me issues! when the system works well its great and keeps the house warm but at the moment, once or twice a week the buffer tank which is a 50l cordivari version seems to vent all the central heating system pressure out of of the aav at the top. i have changed the valve a couple of times but still have the same issue, anyone have any ideas what the issue/s might be?