Summertime, the current return air temperature (AI) is 30°C, and the return air temperature setpoint is the default value of 18°C. After the control program detects that the Unit Start/Stop switch (DI) is closed, it immediately triggers Outside Air Damper Control (AO). The control opens the fan (DO) after 60 seconds and gradually opens the valve (AO) from 0 to 10 V (fully open).
The valve (AO) gradually closes from 10 to 0 V when the return air temperature setpoint is adjusted towards 30 °C. The valve fully closes when the setpoint is higher than 30 °C.
Filter Alarm: Occurs when the filter differential pressure switch (DI) closes after the fan is ON for 30 seconds. The alarm LED (DO) closes and generates an output.
Low Limit Temperature Alarm: Occurs at any time when the low limit temperature protection switch (DI) is open. The alarm output (DO) closes, the outside air damper is OFF with 0 % output and the valve immediately adjusts to fully open (10 V).