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Blower Operation and Adjustments
KD 024 units are equipped with multi-tap ECM, direct
drive blowers only.
KD 036, 048 and 060 units are equipped with either
multi-tap ECM, direct drive or two-stage belt drive
blowers.
The blower will operate at high speed with Y2 thermostat
demand and low speed with a Y1 thermostat demand.
Low speed operation delivers approximately 2/3 of air
volume of high speed. Two-speed blower operation
results in lower energy consumption.
IMPORTANT
Three phase scroll compressors must be phased
sequentially for correct compressor and blower
rotation. Follow “COOLING START-UP” section of
installation instructions to ensure proper compres
sor and blower operation.
A-Blower Operation
Initiate blower demand at thermostat according to
instructions provided with thermostat. Unit will cycle on
thermostat demand. The following steps apply to
applications using a typical electro-mechanical thermostat.
1- Blower operation is manually set at the thermostat
subbase fan switch. With fan switch in
ON
position,
blowers will operate continuously.
2- With fan switch in
AUTO
position, the blowers will
cycle with demand. Blowers and entire unit will be off
when system switch is in
OFF
position.
Belt Drive Blowers
1- Loosen the reusable wire tie which secures the
blower wiring to the blower motor mounting plate.
2- Remove and retain screws on either side of sliding
frame. Pull frame toward outside of unit.
3- Slide frame back into original position when finished
servicing. Reattach the blower wiring in the previous
location on the blower motor base using the wire tie.
4- Replace retained screws on either side of the
sliding frame.
Direct Drive Blowers
1- Loosen the reusable wire tie which secures the
controls and high voltage blower wiring to the blower
housing.
2- Remove and retain screws in front and on either side
of blower housing. Pull frame toward outside of unit.
3- Slide frame back into original position when finished
servicing. Reattach the blower wiring in the previous
location on the blower motor base using the wire tie.
4- Replace retained screws in front and on either side of
the blower housing.
B-Determining Unit CFM - Direct Drive Blowers
1- The following measurements must be made with air
filters in place.
2- With all access panels in place, measure static
pressure external to unit (from supply to return). Add
any additional air resistance for options and
accessories shown in accessory air resistance tables.
Blower performance data is based on static pressure
readings taken in locations shown in figure 15.
Note - Static pressure readings can vary if not taken
where shown.
3- Use figure 16 to determine the factory-set blower
speed.
FIGURE 15
LOCATION OF STATIC PRESSURE READINGS
SUPPLY AIR
READING
LOCATION
SUPPLY
RE
TURN
INSTALLATIONS WITH DUCTWORK
SUPPLY
RE
TURN
INSTALLATIONS WITH CEILING DIFFUSERS
MAIN
DUCT RUN
FIRST BRANCH
OFF OF MAIN RUN
DIFFUSER
ROOFTOP UNIT
ROOFTOP UNIT
SUPPLY AIR
READING
LOCATION
RETURN AIR
READING LOCATION
RETURN AIR
READING
LOCATION