This option adds three AOs (OAD-O, EAD-O, and RAD-O) to provide damper control for the unit mixing dampers. If you select Variable Speed Relief Fan, this option is not available. When this option is selected and cooling is needed, the OAD-O damper is fully open and the RAD-O damper closes as part of the discharge air temperature (DAT) loop prior to the use of any cooling coil. The EAD-O damper shall track RAD-O inversely. If free cooling is unavailable, minimum ventilation is maintained by the minimum outdoor airflow loop a maximum RAD-O position.