HEAT ANTICIPATOR SETPOINT
It is important that the anticipator setpoint be correct. Too high a
setting results in longer heat cycles and a greater temperature
swing in the conditioned space. Reducing the value below the
correct setpoint causes shorter “ON” cycles and may result in
the lowering of the temperature within the conditioned space.
Refer to Table 9 for the required heat anticipator setting.
CHECKING SUPPLY AIRFLOW
The RPM of the supply air blower will depend on the required
airflow, 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 and the motor
pulley adjustment (turns open) can be determined from the
blower performance data in Table 4.
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.
BELT DRIVE BLOWER
All units have belt drive single-speed blower motors. The
variable pitch pulley on the blower motor can be adjusted to
obtain the desired supply air flow.
Note the following:
1. The supply airflow must be within the limitations shown in
Table 1.
2. Pulleys can be adjusted in half turn increments.
3. The tension on the belt should be adjusted as shown in
Figure 8.
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 airflow after the initial balancing has been
completed:
1. Remove the two dot plugs from the blower motor and the fil-
ter access panels shown in Figure 7.
2. Insert at least 200mm (8") of tubing (approximately 6mm
(1/4") diameter) into each of these holes for sufficient pene-
tration into the air flow on both sides of the 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 en-
sure a dry coil, the compressors should be de-energized
while the test is being run.
4. Knowing the pressure drop across a dry coil, the actual air
flow through the unit and clean filters, can be determined
from the curve in Figure 9.
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
reinstall the two dot plugs that were removed in Step 1.
NOTE: DE-ENERGIZE THE COMPRESSORS BEFORE
TAKING ANY TEST MEASUREMENTS TO ENSURE
A DRY INDOOR COIL.
035-18895-000-A-0902
Unitary Products Group
13
HEATER
kW
SETTING, AMPS
TH1
TH2
18
0.29
-
36
0.29
0.29
54
0.29
0.29
72
0.29
0.29
TABLE 9 - HEAT ANTICIPATOR SETTING
TURNS
OPEN*
BLOWER DRIVE RANGE (RPM)
180 UNIT
6
845
5
885
4
925
3
960
2
1000
1
1040
*Pulleys can be adjusted in half-turn increments.
Do NOT close pulley below 1 turn open.
TABLE 10 - SUPPLY AIR BLOWER MOTOR PULLEY
ADJUSTMENT
NOMINAL CFM (THOUSANDS) SUPPLY AIR
4
5
6
7
8
9
10
0.65
0.55
0.45
0.35
0.25
180 MBH
P
R
E
S
S
U
R
E
D
R
O
P
(
iw
g
)
1.61
1.36
1.12
81
62
P
R
E
S
S
U
R
E
D
R
O
P
(
P
a
)
m
3
/s SUPPLY AIR
1.9
2.4
2.8
3.3
3.8
4.2
4.7
FIG. 9 - PRESSURE DROP ACROSS A DRY INDOOR
COIL VS SUPPLY AIRFLOW
FIG. 8 - BELT ADJUSTMENT
