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B-Blower Access
1. Disconnect jack/plug connector to blower motor. Also
disconnect jack/plug connector heating limit switches
on gas units.
2. Remove screws on either side of blower assembly slid
ing base. See figure 9.
3. Pull base toward outside of unit.
C-Determining Unit CFM
IMPORTANT - Multi-staged supply air units are factory-
set to run the blower at full speed when there is a blower
(G) demand without a heating or cooling demand. Refer
to the field-provided, design specified CFM for all modes
of operation. Use the following procedure to adjust motor
pulley to deliver the highest CFM called for in the design
spec. See Inverter Start-Up section to set blower CFM for
all modes once the motor pulley is set.
1. The following measurements must be made with a dry
indoor coil. Run blower (G demand) without a cooling
demand. Measure the indoor blower shaft RPM. Air fil
ters must be in place when measurements are taken.
2. With all access panels in place, measure static pres
sure external to unit (from supply to return). Blower per
formance data is based on static pressure readings
taken in locations shown in figure 8.
Note - Static pressure readings can vary if not taken where
shown.
3. See table of contents for Blower Data and or Optional
Accessories. Use static pressure and RPM readings to
determine unit CFM.
4. The blower RPM can be adjusted at the motor pulley.
Loosen Allen screw and turn adjustable pulley clock
wise to increase CFM. Turn counterclockwise to de
crease CFM. See figure 9. Do not exceed minimum and
maximum number of pulley turns as shown in table 5.
TABLE 5
MINIMUM AND MAXIMUM PULLEY ADJUSTMENT
Belt Minimum Turns Open Maximum Turns Open
A Section No minimum 5
B Section 1* 6
*No minimum number of turns open when B belt is used on
pulleys 6” O.D. or larger.
FIGURE 8
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
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