Application 2565 VAV Series Fan Powered with Hot
In Application 2565, the controller modulates the supply air damper of the terminal box for
cooling and modulates a hot water valve for heating. When in heating, the terminal box either
maintains minimum airflow or modulates the supply air damper. The terminal box also has a
series fan for air circulation. In order for the terminal box to work properly, the central air
handling unit must provide supply air. See Figure 12.
On series fan powered terminal boxes, the terminal box fan must be
controlled/interlocked to start either before or at the same time as the central air
handler. Failure to do so may cause the terminal box fan to rotate backwards and
cause consequent damage at start up.
In day mode, the fan is ON all the time. In night mode, the fan cycles on when heating or
cooling is required.
3 to 5 Straight Duct Diameters
required for proper sensor reading
Figure 12. Application 2565 Control Drawing.
"COMMON" Termination for all DOs
Wall Switch (Opt.)
Siemens Building Technologies, Inc.