Page 7
507111-02 2/2015
Blower Operation and Adjustments
Units are equipped with belt drive blowers; available
drive varies by model.
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- Set thermostat or temperature control device fan
switch to
AUTO
or
ON.
With fan switch in
ON
position,
blower will operate continuously. With fan switch in
AUTO
position, the blower will cycle with demand.
2- Blower and entire unit will be off when thermostat or
temperature control device system switch is in
OFF
position.
B - Determining Unit CFM
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).
Blower performance data is based on static pressure
readings taken in locations shown in figure 9.
Note - Static pressure readings can vary if not taken
where shown.
3- Measure the indoor blower wheel RPM.
4- Referring to pages 9-14, use static pressure and
RPM readings to determine unit CFM. Use
option/accessory air resistance table on page 15
when installing units with any of the options or
accessories listed. Refer to table 3 for minimum
airflow when electric heat is installed.
5- The blower RPM can be adjusted at the motor pulley.
Loosen Allen screw and turn adjustable pulley
clockwise to increase CFM. Turn counterclockwise to
decrease CFM. See figure 10. Do not exceed
minimum and maximum number of pulley turns as
shown in table 1.
TABLE 1
MINIMUM AND MAXIMUM PULLEY ADJUSTMENT
Belt
Min. Turns Open
Maxi. Turns Open
A Section
No minimum
5
C - Blower Belt Adjustment
Maximum life and wear can be obtained from belts only if
proper pulley alignment and belt tension are maintained.
Tension new belts after a 24-48 hour period of operation.
This will allow belt to stretch and seat grooves. Make sure
blower and motor pulley are aligned as shown in figure 11.
FIGURE 9
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
