The AAV is used for releasing air from they hybrid system. Install one per fan coil unit at the highest point of the pipework. The AAV is supplied with a 15mm compression end for fitting directly onto copper tube. For barrier pipe systems the nut and olive is removed leaving a 1/2" male thread which can be screwed into an iron tee with a 1/2" female thread.
This air vent is designed to automatically remove any air trapped inside the wet side of the hybrid system.