air in heating system

[ambrosia]

got a really old heating system, F and E tank in loft, one zone valve to control the heating, hot water on constantly, old potterton cast iron boiler.

none of the radiators are getting particularly hot (water is okay), colleague diagnosed circulation problem and did a powerflush, he also replaced the AAV

it didnt work and now the problem has been passed to me

When I got there I found the system was full of air so i bleed all the radiators, I also noticed the vent pipe from the FandE doesnt join the heating system on the same stretch of pipe as the cold feed, odd but at the time i assumed this couldnt accout for all the air in the system

the pump pushes toward the AAV and the new AVV has clearly been under pressure the cap has dissapeared and it has signs water has been forced out

anyway 3 days later all the rads needed bleeding again and has sucked in so much air one of the rads has become airlocked (presumably) and will need a wet vac to get it going again

I'm out of my comfort zone, i living in london and 99% of my jobs are simple combi boilers

Any suggestions what to do next, I isolated the AAV because thats my best guess of where the air is getting in

has the powerflush caused a worst blockage, the system was working and has worked for decade

 

[erpkid]

Could just be air-locked aggravated by poor pipe layout. That there was an AAV supports this. The new gas you are bleeding off after 3 days may have been there all along. Worth sequentially closing all bar one rad throughout the system to chase any air locks. A new AAV should not let air in - the power flush should have helped rather than hinder. If you have to vac to get it going then the layout is very poor. Best of luck.