Belt Drive Supply Air Inverter Start-Up - Lennox KHC092 Installation Instructions Manual

Supply Air Inverter Start-Up
A-General
Units provide three blower speeds. The blower will
operate at lower speeds when cooling demand is low and
higher speeds when cooling demand is high. This results
in lower energy consumption. See table 12 for detailed
unit operation.
Inverter-driven blowers will operate at high speed during
ventilation (blower "G" only signal) but can be adjusted to
operate at low speed.
Low speed is approximately 66% of the full speed RPM
and medium speed is 75% of the full speed RPM.
B-Set Maximum Blower CFM
1- Initiate a blower (G) only signal from the room
thermostat or control system.
2- Adjust the blower pulley to deliver the full (high
speed) CFM in the typical manner. See Determining
Unit CFM in the Blower Operation and Adjustment
section.
Note - The following sections detail how to set ventilation
speeds and minimum damper positions on units with
standard economizers. On units with high performance
economizers, ventilation speeds and three separate
damper positions must be programmed via the
economizer controller
installation instructions
economizer application guide provided with the unit for
further instructions.
C-Set Blower Speed During Ventilation (Units With
Standard Economizers Only)
To save energy during ventilation, the blower speed can
be set to low. This is accomplished by changing the
ventilation speed switch on the VFD control board to "LO".
See figure 16.
Note - On units equipped with a standard economizer, set
damper minimum position as shown in the next section.
After adjusting the low speed minimum position, the
ventilation speed switch will be in the "LO" position.
display. See economizer
and high performance
LVC2 (A183) VFD CONTROL BOARD
VENTILATION
SPEED SWITCH
POWER
LED
LOW SPEED
MINIMUM POSITION
POTENTIOMETER
D-Set Damper Minimum Position (Units With Standard
Economizers Only)
To maintain required minimum ventilation air volumes
when the unit is in the occupied mode, two minimum
damper positions must be set. A high and a low speed
potentiometer are provided on the VFD control board to
adjust minimum damper position. See figure 16. The low
speed minimum damper position is used for both low and
medium blower speeds as standard economizers only
offer 2 damper positions.
Set High Speed Minimum Position
1- Initiate a blower (G) only AND occupied demand from
the room thermostat or control system.
2- Set the ventilation speed switch on the VFD control
board to "HI".
3- Rotate the high speed potentiometer on the VFD
control board to set the high speed minimum damper
position.
4- Measure the intake air CFM. If the CFM is lower than
the design specified CFM for ventilation air, use the
potentiometer 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 18
HIGH SPEED
MINIMUM POSITION
POTENTIOMETER
FIGURE 16