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VIII--Multi-Staged Blower
A-Design Specifications
Use the “Blower CFM Design Specifications” table at
tached to the unit (table 18 in the installation instructions) to
fill in test and balance values when setting up the unit.
If only high and low cooling design specifications are pro
vided, set the medium cooling CFM at the high or low cool
ing design spec or any CFM between.
B-Set Maximum CFM
Use the attached table to determine highest blower CFM
for appropriate unit. Adjust the blower pulley to deliver that
amount of CFM with only the blower operating. See Deter
mining Unit CFM in the Blower Operation and Adjustment
section.
C-Set Blower Speeds
1. Use the following mobile service app menu to enter the
blower design specified CFM into the Unit Controller.
Make sure blower CFM is within limitations shown in ta
ble 20 or 21. Refer to the Unit Controller manual provid
ed with unit.
RTU MENU > RTU OPTIONS > BLOWER > SPEED
2. Enter the following design specifications as shown in
the attached table.
Blower / Heat CFM
Cooling High CFM
Cooling Low CFM
Vent CFM
3. Adjust the blower RPM to deliver the target CFM based
on the measured static pressure using the blower ta
ble.
4. Measure the static pressure again and apply the static
pressure and RPM to the blower tables to determine
adjusted CFM.
5. Repeat adjustments until design CFM is reached.
D-Set Damper Minimum Position
To maintain required minimum ventilation air volumes when
the unit is in the occupied mode, two minimum damper posi
tions must be set.
The Unit Controller will open the damper to “Min OCP Blwr
High” when blower CFM is at or ABOVE the “midpoint”
CFM.
The Unit Controller will open the dampers to “Min OCP Blwr
Low” when blower CFM is BELOW a “midpoint” CFM.
The Unit Controller will calculate the “midpoint” CFM.
*Available blower speeds vary by unit and thermostat stages.
Set Minimum Position 1
Use the following mobile service app menu to set “Min OCP
Blwr High” for the blower CFM above the “midpoint” CFM.
When navigating into this menu, the Unit Controller will run
damper calibration and allow damper position adjustment.
RTU MENU > SETTINGS > RTU OPTIONS > DAMPER
Tap "Next" to skip tabs and complete damper position cali
bration until "Damper Calibration Blower Speed High" tab
appears.
Measure the intake air CFM. If the CFM is lower than the
design specified CFM for ventilation air, use the Unit Con
troller to increase the damper percent open. If the CFM is
higher than specified, decrease the damper percent open.
Note - Intake air CFM can also be determined using the out
door air temperature, return air temperature and mixed air
temperature. Refer to the economizer or outdoor air damp
er installation instructions.
Set Minimum Position 2
Use the following mobile service app menu in the Unit Con
troller to set “Min OCP Blwr Low” for the blower CFM below
the “midpoint” CFM. When navigating into this menu, the
Unit Controller will run damper calibration and allow damp
er position adjustment.
RTU MENU > SETTINGS > RTU OPTIONS > DAMPER
Tap "Next" to skip tabs and complete damper position cali
bration until "Damper Calibration Blower Speed High" tab
appears.
Measure the intake air CFM. If the CFM is lower than the
design specified CFM for ventilation air, use the Unit Con
troller to increase the damper percent open. If the CFM is
higher than specified, decrease the damper percent open.
Note - Intake air CFM can also be determined using the out
door air temperature, return air temperature and mixed air
temperature. Refer to the economizer or outdoor air damp
er installation instructions.
E-Inverter Bypass Option
The supply air inverter is factory-set to by-pass the inverter
manually. To by-pass the inverter and operate the blower in
the constant air volume mode, use the following Unit Con
troller menu and set to “engaged”:
SETTINGS > RTU OPTIONS > BLOWER > VFD BY
PASS
To configure the unit to by-pass the inverter automatically,
use the following Unit Controller menu.
SETUP > INSTALL
Press SAVE until the menu reads:
CONFIGURATION ID 1
Change the 6
th
character position to A for automatic bypass
option.
Press SAVE
Caution - Units not equipped with an inverter will have the
6
th
character set to N, indicating the inverter is not by
passed. The blower motor could be damaged and/or result
in product or property damage if the setting is changed to
automatic or manual.
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