Lennox LGM Series - Multi-Staged Blower Operation; Design Specifications for Blower CFM; Set Maximum Blower CFM; Set Blower Speeds

Page 48
IX--Multi-Staged Blower

       -
tached to the unit (table 18 in the installation instructions)

-
ed, set the medium cooling CFM at the high or low cooling
design spec or any CFM between.
B-Set Maximum CFM
Use 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 D ter-
mining Unit CFM in the Blower Operation and Adjustment
section.
C-Set Blower Speeds
1 - 1. Use the following mobile service app menu to
        
Controller. Make sure blower CFM is within limitations
shown in table 24 or 25 . Refer to the Unit Controller
manual provided with unit.
RTU MENU > RTU OPTIONS > BLOWER > SPEED
2 - 
in the attached table (table18 in the installation
instructions).
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 table.
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 positions 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 ad-
justment.
RTU MENU > SETTINGS > RTU OPTIONS > DAMPER
Tap “Next” to skip tabs and complete damper position cal-
ibration until “Damper Calibration Blower Speed High” tab
appears.
Measure the intake air CFM. If the CFM is lower than the
-
troller to increase the damper percent open. If the CFM is

NOTE - Intake air CFM can also be determined using the
outdoor air temperature, return air temperature and mixed
air temperature. Refer to the economizer or outdoor air
damper installation instructions.
Set Minimum Position 2
Use the following mobile service app menu in the Unit
Controller 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 damper position adjustment.
RTU MENU > SETTINGS > RTU OPTIONS > DAMPER
Tap “Next” to skip tabs and complete damper position cal-
ibration until “Damper Calibration Blower Speed High” tab
appears.Measure the intake air CFM. If the CFM is lower

Unit Controller to increase the damper percent open. If
        
percent open.
Note - Intake air CFM can also be determined using the
outdoor air temperature, return air temperature and mixed
air temperature. Refer to the economizer or outdoor air
damper installation instructions.
E-Inverter Bypass Option
The supply air inverter is factory-set to by-pass the invert-
er manually. To by-pass the inverter and operate the blow-
er in the constant air volume mode, use the following Unit
Controller menu and set to “engaged”:
SETTINGS > RTU OPTIONS > BLOWER > VFD BYPASS

use the following Unit Controller menu.
SETUP > INSTALL
Press SAVE until the menu reads:
CONFIGURATION ID 1
-
pass option.
Press SAVE
Caution - Units not equipped with an inverter will have the
6th 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.