Page 6 of 9
507708-01
Issue 1337
Cooling Cycle Charge Adjustment Procedure
Units with Indoor Pistons
Units installed with indoor pistons require charging
with the superheat method.
The following procedure is valid when indoor airflow is
within ± 20 % of its rated CFM.
1. Operate unit a minimum of 10 minutes before
checking charge.
2. Measure suction pressure by attaching a gage to
suction valve service port. Determine saturation
temp from T/P chart.
3. Measure suction temperature by attaching an
accurate thermistor type or electronic thermometer
to suction line at service valve.
4. Calculate superheat (measured temp. - saturation
temp.) .
5. Measure outdoor air dry-bulb temperature with
thermometer.
6. Measure indoor air (entering indoor coil) wet-bulb
temperature with a sling psychrometer.
7. Compare superheat reading at service valve with
the chart located on control box cover.
8. If unit has a higher suction line temperature than
charted temperature, add refrigerant until charted
temperature is reached,
9. If unit has a lower suction line temperature than
charted temperature, reclaim refrigerant until
charted temperature is reached.
10. Remove charge if superheat is low and add charge
if superheat is high.
Units with Indoor TXV
Units installed with cooling mode TXV require charging
with the subcooling method.
1. Operate unit a minimum of 10 minutes before
checking charge.
2. Measure liquid service valve pressure by
attaching an accurate gage to service port.
Determine saturation temp. from T/P chart.
3. Measure liquid line temperature by attaching an
accurate thermistor type or electronic thermometer
to liquid line near outdoor coil.
4. Calculate subcooling (saturation temp. - measured
temp.) and compare to table on back of control box
cover.
5. Add refrigerant if subcooling is lower than range
shown in table. Recover refrigerant to decrease
subcooling.
6. If ambient temp. is lower than 65° F, weigh
refrigerant according to the name plate data.
NOTE: If a TXV is installed on indoor unit, a hard start
kit will be required on all models with
reciprocating compressors. Refer to the
specification sheet for details. Hard start kits
are also recommended for areas with utility
power lower than 208 Vac.
SYSTEM OPERATION
The outdoor unit and indoor blower cycle on demand
from the room thermostat. When the thermostat blower
switch is in the ON position, the indoor blower operates
continuously.
Filter Drier
The filter drier is very important for proper system
operation and reliability. If the drier is shipped loose, it
must be installed by the installer in the field. Unit warranty
will be void, if the drier is not installed.
