Multi-Staged Air Volume Start-Up - Lennox LGT156H Installation Instructions Manual

Multi-Staged Air Volume Start-Up

A-Design Specifications
Use table 17 to fill in field-provided, design specified
blower CFM for appropriate unit.
If only high and low cooling design specifications are
provided, set the medium cooling CFM at the high or low
cooling design spec or any CFM between.
B-Set Maximum CFM
Use table 17 to determine highest blower CFM for
appropriate unit. Adjust the blower pulley to deliver that
amount of CFM with only the blower operating. See
Determining 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 table 18 or 19. Refer to the Unit
Controller manual provided with unit.
RTU MENU > RTU OPTIONS > BLOWER > SPEED
2- Enter the following design specifications as shown in
table 17.
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.
LGT/LCT156, 180, 210, 240, 300
Blower CFM Design Specifications
T'Stat or
Unit
Zone Con­
trol Stages
156
180
210
240
300
*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
calibration 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
Controller 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.
Page 60
TABLE 17
Blower Speed
Htg.
Clg. High
2
Clg. Low
Ventilation
Htg.
Clg. High
2
Clg. Low
Ventilation
Htg.
Clg. High
2
Clg. Low
Ventilation
Htg.
Clg. High
2
Clg. Low
Ventilation
Htg.
Clg. High
2
Clg. Low
Ventilation
Design
Specified
CFM