Does the AAV work on Closed and Open systems?
Yes, on newly installed closed systems there will be a small pressure drop (around 15%) as the air is vented from the fresh water, but any further pressure drop will be due to loss of system water (leaks). Some installers are priming a newly installed system to about 10% more than it’s operating pressure to compensate on a system fitted with AAV’s. ” On a Closed system will fitting automatic vents cause the pressure to drop to zero and the boiler stop operating?” The answer is linked to the above – continual venting will be due to new air entering the system (through microgaps in joints etc), once the fresh water has vented its 15% of air the volume of water cannot further reduce in size – so if you still experience pressure drop it’s due to water loss.
