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DN-Series Integrated Programmable Controls
DOAS
34
The SA flow setpoint is derived from the user entered minimum and maximum CO2 levels and
minimum and maximum desired airflow rates. When the CO2 level is at or below the minimum
CO2 level the airflow setpoint is at the minimum and when the CO2 level is at or above the
maximum CO2 level the airflow setpoint is at the maximum. Between the minimum and
maximum CO2 levels the airflow setpoint is linearly scaled. If the measured CO2 level exceeds
1000 ppm (adjustable) for more than 60 seconds (adjustable) a CO2 alarm will be set to true.
This supply fan operation mode can be used to provide demand-controlled ventilation of a
space. The minimum fan speed will provide the required minimum outdoor air when the CO2
level is at or below the CO2 setpoint.
OA CFM SETPOINT
1400
1200
1000
800
0
200
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600
0
1200
1000
800
600
400
200
UNIT OPERATION
Units with a VFD or ECM for the exhaust fan can control the fan for fixed speed, EA flow control,
supply fan command tracking control, supply fan flow rate tracking control, or return static
pressure control.
5.3.1 Constant Fan Speed Option
The analog voltage command to the exhaust fan VFD or ECM can be set from the unit controller
display or by the BMS.
The adjustable range of 0% to 100% correspond to the minimum and maximum fan operating
speed. This exhaust fan operation mode can be used to field balance the EA flow rate.
5.3 OPTIONS FOR EXHAUST FAN CONTROL
