Viii-Direct Drive Supply Air Blower - Lennox LGT Series Unit Information

VIII-Direct Drive Supply Air Inverter
If a test and balance contractor has not commissioned the
unit, use this section to set supply air CFM.
A-Set Blower Speed
1 - Use table 16 to fill in field-provided, design specified
blower CFM.
TABLE 16
Blower CFM Design Specifications
Blower Speed
Heating
Cooling High
Cooling Medium
Cooling Low
Ventilation
2 - Use the following menu to enter the blower design
specified CFM into the Unit Controller. Don't press
"SAVE" until all CFM are entered. Make sure blower
CFM is within limitations shown in table 13. Refer to
the Unit Controller manual provided with unit.
SETUP > TEST & BALANCE > BLOWER
3 - Once all four speeds are entered, the target (highest
of the heating and cooling settings) CFM and default
RPM will be displayed.
Note - When units are not equipped with heat, the
Blower Heat speed will not be displayed. Blower
Cooling High will be the first blower speed to appear.
4 - Measure the static pressure as shown in the Blower
Start-Up section. Use the static pressure, target
CFM and blower tables to determine the RPM
needed. Values in the blower table reflect the static
pressures taken in locations shown in figure 9.
5 - Enter the RPM and repeat the previous step until
the design CFM is reached.
6 - Press SAVE followed by MAIN MENU.
Note - Once the CFM settings are saved, the Unit
Controller will set all other blower CFM.
B-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 dampers to "Min OCP Blwr Low" when blower
CFM is BELOW a "midpoint" CFM. The Unit Controller will
open the damper to "Min OCP Blwr High" when blower
CFM is at or ABOVE the "midpoint" CFM.
Design Specified CFM
Page 49
The Unit Controller will calculate the "midpoint" CFM.
Set Minimum Position 1
Use the following 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 bring on the corresponding blower speed and allow
damper position adjustment.
SETTINGS > RTU Options > EDIT PARAMETER > EN-
TER DATA ID - 9 > MIN DAMPER LOW BLOWER = X.X
%
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
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 same menu in the Unit Controller to set "Min OCP
Blwr High" for the blower CFM above the "midpoint" CFM.
When navigating into this menu, the Unit Controller will
bring on the corresponding blower speed and allow damp-
er position adjustment.
SETTINGS > RTU OPTIONS > DAMPER > MIN DAMP-
ER POSITION BLOWER ON HIGH = X.X %
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
outdoor air temperature, return air temperature and mixed
air temperature. Refer to the economizer or outdoor air
damper installation instructions.
TABLE 17
MINIMUM AND MAXIMUM CFM
Gas Heat Minimum CFM
Unit Gas Heat Size
LGT092H-150H
Airflow CFM*
Standard 2150
Medium 2550
High 2600