Thrush AHF Series - Manual (Page 12)

4.2 Operation
Heating/cooling system efficiency and component life is greatly dependent on water
quality. Air and dirt particles can cause pump cavitation, corrosion and increased
component wear. In a closed loop system, the Aar-O-Vent eliminates air bubbles,
entrained air and dirt particles quickly and easily.
Air Elimination:
Thrush Co. offers the Aar-O-Vent in “Air Only”, “Dirt Only” and combination units “Air
and Dirt”. The “Air Only” and “Air & Dirt” units are the only models that utilize the
Thrush Model 720 air elimination device, air vent. They also have extra space in the
top of the vessel for the collection of air. Outlined below is operational information on
the air elimination feature of the Aar-O-Vent. Use Figure 4-2 for reference (“Air and
Dirt” model shown).
 Large air bubbles in the system water enter the Aar-O-Vent and collide with the
coalescing medium. They quickly rise to the top of the vessel and into the air
elimination device.
 Micro bubbles coalesce and form larger bubbles. The larger bubbles then rise to
the top of the vessel and into the air elimination device.
 Entrained air is pulled out of solution and forms micro bubbles. The micro bubbles
coalesce forming larger bubbles. The larger bubbles rise to the top of the vessel
and into the air elimination device.
 As air bubbles collect at the top of the vessel they create an air pocket. This
pocket of air pushes the water level down inside the vessel. As the water level
drops, the float inside of the air elimination device also drops releasing the air to
atmosphere.
 The air elimination device releases air as fast as it can be separated. It will not
allow air back into the system, even if a vacuum occurs.
 Once the air has been released, the water level will rise inside the vessel. This
causes the float to rise and close the air elimination device.
This cycle will continue as new water is introduced into the system piping. With each
pass of system water the Aar-O-Vent will eventually eliminate up to 99.7% of
dissolved oxygen content in the system piping.
The Aar-O-Vent is not designed to be used as a make-up water inlet point. Using
any of the connections for make-up water would impede proper operation and
void the warranty.
Thrush Co.
Manual #9636-1230