Posted by Harold Kestenholz - Hydronic Network on November 20, 2001 at 12:28:53:
In Reply to: Vacuum vent valves posted by Andrey on November 20, 2001 at 10:15:09:
Vacuum vent valves work on vacuum steam systems. If you don't have one, the vents will do harm. Vacuum vents were designed for coal fired systems where the fire was on all the time and banked slowly at night.
http://www.bellgossett.com/Press/vacuum.html