| The Hy-vent is the air eliminator. It is usually mounted on a tapping on the boiler, or from your description, mounted on an air scoop in-line with the boiler piping, which often also has the expansion tank attached at the bottom. Or maybe it's just sitting at the top of an elbow.
If you have had air problems for 5 years, but the system otherwise heats the building OK, then you most likely have a 'not pumping away' problem causing the air noise.
10 psi system pressure cold is a bit low. Bump it up to 12-15. If the hot pressure gets into the 22+ range, keep an eye on the relief valve. If it starts to weep, drain a small bit of water to get the pressure back down. But this still won't cure the air noise problem, unless there's something else going on with your system that we don't know about.
Moving the expansion tank connection is usually pretty simple. Consider snapping some pics of the boiler and adjacent piping. Host them at photobucket of similar hosting site and provide links here. |