7. Refer to Required Suction Tube Temp. in Superheat Charging Table. Find superheat temperature located in
Step 6 and suction pressure. At this intersection note suction line temperature.
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. If outdoor air temperature or pressure at suction port changes, charge to new suction line temperature
indicated on chart.
Low Charge Cooling 50ZPM Unit 60, TXV Metering Device:
1. Measure discharge line pressure by attaching a gauge to the service port.
2. Measure the liquid line temperature by attaching a temperature sensing device to it.
3. Insulate the temperature sensing device so that the outdoor ambient doesn’t affect the reading.
4. Refer to the required Subcooling Chart to find the required subcooling based on the model type and the
outdoor ambient temperature.
5. Interpolate if the outdoor temperature lies in between the table values.
6. Find the pressure value corresponding to the measured pressure on the compressor discharge line.
7. Read across from the pressure reading to obtain the Liquid line temperature for a required subcooling.
8. Add charge if the measured temperature is higher than the liquid line temperature value in the table.
9. Remove charge if the measured temperature is lower than the table value.
Step 4 — Indoor Airflow and Airflow Adjustments
Table 2 shows wet coil air delivery for horizontal discharge units. Table 3 and Table 4 show pressure drops.
NOTE
: Be sure that all supply-and return-air grilles are open, free from obstructions, and adjusted properly.
Blower speed tap can be changed by replacing the factory installed blue low speed tap wire (cooling) with the unused
black high speed wire in unit control box. The red medium speed wire is factory installed to operate with a call for
supplemental electric heat. See unit wiring diagram. Be sure new airflow meets the range noted above the minimum
electric heat CFM, if equipped. Refer to Table 2. All model sizes are factory wired for rated airflow operation.
Step 5 — Sequence of Operation
FAN OPERATION - The FAN switch on the thermostat controls indoor fan operation. When the FAN switch is placed
in the ON position, the indoor (evaporator) fan motor (IFM) is energized through the G terminal on the thermostat. The
motor’s internal logic then provides power to the indoor (evaporator) fan motor (IFM). The IFM will run continuously
when the FAN switch is set to ON. When the FAN switch is set to AUTO, the thermostat de-energizes the IFM
(provided there is not a call for cooling).
WARNING
UNIT OPERATION HAZARD
Failure to follow this caution may result in equipment damage or improper operation.
For cooling operation, the recommended airflow is 350 to 450 cfm for each 12,000 Btuh of rated cooling capacity.
WARNING
ELECTRIC SHOCK HAZARD
Failure to follow this warning could result in personal injury or death.
Disconnect electrical power to the unit and install lockout tag before changing blower speed.
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