Carrier 38AUZ*07 Series Installation, Start-up And Service Instructions Manual

Contents

20Advanced Scroll Temperature Protection (ASTP)A label located above the terminal box identifies CopelandScroll compressor models that contain this technology. See Fig.17. Advanced Scroll Temperature Protection (ASTP) is a formof internal discharge temperature protection, that unloads thescroll compressor when the internal temperature reaches ap-proximately 300°F. At this temperature, an internal bi-metaldisk valve opens and causes the scroll elements to separate,which stops compression. Suction and discharge pressures bal-ance while the motor continues to run. The longer the compres-sor runs unloaded, the longer it must cool before the bi-metaldisk resets. See Fig. 18.Fig. 17 — Advanced Scroll TemperatureProtection LabelFig. 18 — Recommended Minimum Cool-Down TimeAfter Compressor is StoppedTo manually reset ASTP, the compressor should be stoppedand allowed to cool. If the compressor is not stopped, the motorwill run until the motor protector trips, which occurs up to90 minutes later. Advanced Scroll Temperature Protection willreset automatically before the motor protector resets, whichmay take up to 2 hours.Start UnitSet the space thermostat to a set point above space temperatureso that there is no demand for cooling. Close the 38 AU discon-nect switch. Only the crankcase heater will be energized.Reset the space thermostat below space temperature so that acall for cooling is ensured.Adjust Refrigerant ChargeThe unit must be charged in Cooling mode only. Refer to Cool-ing Charging Charts, Fig. 19 through Fig. 22. Vary refrigerantuntil the conditions of the chart are met. Note that the chargingcharts are different from the type normally used. The charts arebased on charging the units to the correct subcooling for thevarious operating conditions. Accurate pressure gage and tem-perature sensing device are required. Connect the pressuregage to the service port on the liquid line service valve. Mountthe temperature sensing device on the liquid line close to theliquid line service valve, and insulate it so that outdoor ambienttemperature does not affect the reading. Indoor airflow must bewithin the unit’s normal operating range. Operate the unit for aminimum of 15 minutes. Ensure that pressure and temperaturereadings have stabilized. Plot the liquid pressure and tempera-ture on chart and add or reduce the charge to meet the curve.Adjust the charge to conform with the charging chart, using theliquid pressure and temperature to read the chart.FINAL CHECKSEnsure that all safety controls are operating, control panelcovers are on, and the service panels are in place.01020304050607080901001101200 10 20 30 40 50 60 70 80 90Compressor Unloaded Run Time (Minutes)Recommended Cooling Time(Minutes)*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.Never charge liquid into the low-pressure side of system.Do not overcharge. During charging or removal of refriger-ant, be sure indoor-fan system is operating. Ensure bothoutdoor fan motors are running; bypass any Motormasteror mild-ambient control function.