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DN-Series Integrated Programmable Controls
DOAS
36
5.3.4 Supply Fan Flow Tracking Control Option
The controller will adjust the exhaust fan VFD or ECM command to track the supply fan air
flow rate.
The offset from the SA flow rate is adjustable from -25% to +25%. An adjustable PI loop will
compare the measured EA flow to the airflow rate setpoint and adjust the fan speed. This
exhaust fan operation mode can be used to maintain proportional supply and EA flows as the
supply fan modulates and as the unit filters become loaded.
5.3.5 Return Static Pressure Control Option
The controller will adjust the exhaust fan VFD or ECM command to maintain the return duct
static pressure at a setpoint. This mode cannot be used if the supply fan mode is duct
static control.
UNIT OPERATION
The return duct static pressure measurement is typically a negative pressure value. The return
duct static pressure setpoint is entered and adjusted from the unit controller display or provided
by the BMS. The minimum and maximum values for the RA duct static pressure setpoint are
unit dependent. An adjustable PI loop will compare the measured RA duct static pressure to
the static pressure setpoint and adjust the exhaust fan speed. If the measured static pressure
varies from the desired static pressure by more than 0.05 inches water gauge (adjustable) for
more than 300 seconds (adjustable) a RA static pressure alarm will be set to true. This exhaust
fan operation mode can be used to provide a constant return duct pressure for variable exhaust
systems
