BURNER AIR SHUTTER ADJUSTMENT
Adjust burner shutters so no yellow flame is observed in the
heat exchanger tubes. Refer to Figure 14.
CHECKING SUPPLY AIR CFM
The RPM of the supply air blower will depend on the required CFM,
the unit accessories and the static resistances of both the supply
and the return air duct systems. With this information, the RPM for
the supply air blower can be determined from the blower
performance data in Table 5.
Knowing the required blower RPM and the blower motor HP,
the setting (turns open) for the supply air motor pulley can be
determined from Table 10.
Start the supply air blower motor. Adjust the resistances in both
the supply and the return air duct systems to balance the air
distribution throughout the conditioned space. The job
specifications may require that this balancing be done by
someone other than the equipment installer.
To check the supply air CFM after the initial balancing has been
completed:
1. Remove the dot plugs from the filter access and blower
access panels as shown in Figure 10.
2. Insert at least 8" of 1/4 inch tubing into each of these holes
for sufficient penetration into the air flow on both sides of
the evaporator (or indoor) coil.
NOTE: The tubes must be inserted and held in a position
perpendicular to the air flow so that velocity pres-
sure will not affect the static pressure readings.
3. Using an inclined manometer, determine the pressure drop
across a dry indoor coil. Since the moisture on an indoor
coil may vary greatly, measuring the pressure drop across
a wet coil under field conditions would be inaccurate. To
assure a dry coil, the compressors should be deactivated
while the test is being run.
4. Knowing the pressure drop across a dry coil, the actual
CFM through the unit can be determined from the curve in
Figure 15.
WARNING:Failure to properly adjust the total system air quan-
tity can result in extensive blower damage.
After readings have been obtained, remove the tubes and seal
up the drilled holes in the side panels. 5/16" dot plugs (P/N
029-13880) are available through normal parts ordering
procedures.
NOTE: DE-ENERGIZE THE COMPRESSORS BEFORE TAKING ANY TEST
MEASUREMENTS TO ASSURE A DRY INDOOR COIL.
FIG. 14 - TYPICAL FLAME APPEARANCE
FIG. 15 - PRESSURE DROP ACROSS A DRY INDOOR
COIL VS SUPPLY AIR CFM
TURNS
OPEN*
BLOWER DRIVE RANGE (RPM)
DEG090 DEG120 DEG150
1-1/2 &
2HP
2HP 3HP 3HP 5HP
5 975 860 960
4 1024 906 996
3 1073 952 1032
2 1122 998 1068
1 1171 1044 1104
0 1220 1090 1140
*Pulleys can be adjusted in half-turn increments.
ADJUSTMENT
TABLE 10 - SUPPLY AIR BLOWER MOTOR PULLEY
530.22-N4Y
14 Unitary Products Group
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