Desert Aire Aura QS, Installation And Operation Manual

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the unit was designed for. If this happens, consult the Desert Aire Service
Department 262-946-7400. Prior to any calls to the Desert Aire Service
Department please have the unit serial number and model number.
3.3.1.3 Unit with a VFD
The usage of the VFD controlled blowers allows for a simple way to achieve
the correct speed required for proper air balancing. Starting and stopping of
the blowers shall be controlled by the CM3500 control system outputs.
Therefore, the VFD needs to run in the automatic mode.
CAUTION: When modifying the VFD settings, the minimum speed should
not be set to allow the airflow to fall below the air flow required for the unit as
shown on the unit nameplate. The maximum frequency setting of the blower
motor assembly is 75 Hz.
Since the VFD is being used to set one specific speed, the analog reference
is not used. This should be confirmed by examining the wiring schematic
diagram. If no analog reference signal is connected to the VFD, the drive
will always run at the minimum speed setting when it is commanded on.
Determination of this speed needs to be done during the test and balance
phase of the commissioning by increasing the minimum speed setting, as
a frequency, until the proper CFM is achieved. This frequency should be
recorded near the VFD for future reference.
Once the airflow is adjusted, review the motor current draw. If the current draw
is in excess of the current rating listed on the unit nameplate or the drive is
unable to achieve the airflow at the maximum 75 Hz setting, consult the
Desert Aire Service Department 262-946-7400. Prior to any calls to the
Desert Aire Service Department please have the unit serial number and
model number.
3.3.2 Airflow Balancing for Dedicated Outside Air Systems (DOAS)
Dehumidifiers designed for dedicated outside air operation without unoccupied
recirculation mode have a single flow path for supply air. The unit may have an energy
recovery wheel and an exhaust airstream, but these paths do not mix in a DOAS unit.
A damper is installed on the intake of the units ordered for outdoor installation;
provisions for field installed damper are provided on units to be installed indoors.
Damper actuator is two-position. Damper should be in the fully closed position during
unoccupied mode and fully open in occupied mode. Before starting the balancing
process check the damper to ensure it has fully indexed to the open position, and
check that the ductwork is clear of any obvious restrictions.
Once the outside air damper is fully open, verify the correct airflow. If too little airflow
there is likely too much external static resistance. Evaluate ducts for high restriction or
Desert Aire - QS/QV Manual