ADVANCED SCROLL TEMPERATURE PROTECTION (ASTP) — Advanced Scroll Temperature Protection (ASTP) is a form of internal discharge temperature protection, used in 38AUZ*12 and 38AUZ*14 units, that unloads the scroll com- pressor when the internal temperature reaches approximately 300°F. At this temperature, an internal bi-metal disk valve opens and causes the scroll elements to separate, which stops compression. Suction and discharge pressures balance while the motor continues to run. The longer the compressor runs un- loaded, the longer it must cool before the bi-metal disk resets. See Fig. 14.
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| 120 |
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Time |
| 110 |
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| 100 |
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| 90 |
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Recommended Cooling |
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(Minutes) | 80 |
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70 |
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60 |
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50 |
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40 |
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30 |
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20 |
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10 |
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| 0 |
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| 0 | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 |
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| Compressor Unloaded Run Time (Minutes) |
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*Times are approximate.
NOTE: Various factors, including high humidity, high ambient tem- perature, and the presence of a sound blanket will increase cool- down times.
Fig. 14 — Recommended Minimum
After Compressor is Stopped
To manually reset ASTP, the compressor should be stopped and allowed to cool. If the compressor is not stopped, the motor will run until the motor protector trips, which occurs up to 90 minutes later. Advanced Scroll Temperature Protection will reset automatically before the motor protector resets, which may take up to 2 hours. A label located above the terminal box identifies Copeland Scroll compressor models (ZP103 and ZP137) that contain this technology. See Fig. 15.
START UNIT — The field disconnect is closed, the indoor fan circuit breaker is closed, and the space thermostat is set above ambient so that there is no demand for cooling. Only the crankcase heater will be energized.
Reset the space thermostat below ambient so that a call for cooling is ensured.
Never charge liquid into the
ADJUST REFRIGERANT CHARGE — The unit must be charged in Cooling mode only. Refer to Cooling Charging Charts, Fig. 16 through Fig. 19. For applications with line lengths greater than 100 ft, contact Carrier representative. Vary refrigerant until the conditions of the chart are met. Note that the charging charts are different from the type normally used. The charts are based on charging the units to the correct sub- cooling for the various operating conditions. Accurate pressure gage and temperature sensing device are required. Connect the pressure gage to the service port on the liquid line service valve. Mount the temperature sensing device on the liquid line close to the liquid line service valve, and insulate it so that out- door ambient temperature does not affect the reading. Indoor airflow must be within the unit’s normal operating range. Oper- ate the unit for a minimum of 15 minutes. Ensure that pressure and temperature readings have stabilized. Plot the liquid pres- sure and temperature on chart and add or reduce the charge to meet the curve. Adjust the charge to conform with the charging chart, using the liquid pressure and temperature to read the chart.
FINAL CHECKS — Ensure that all safety controls are operating, control panel covers are on, and the service panels are in place.
Fig. 15 — Advanced Scroll Temperature
Protection Label
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