Carrier 38AUQ Advanced Scroll Temperature Protection Astp, Start Unit, Adjust Refrigerant Charge

Advanced Scroll Temperature Protection (ASTP)

A label located above the terminal box identifies Copeland Scroll compressor models that contain this technology. See Fig.

14.Advanced Scroll Temperature Protection (ASTP) is a form of internal discharge temperature protection, that unloads the scroll compressor when the internal temperature reaches ap- proximately 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 bal- ance while the motor continues to run. The longer the compres- sor runs unloaded, the longer it must cool before the bi-metal disk resets. See Fig. 15.

Fig. 14 — Advanced Scroll Temperature

Protection Label

		120
Time		110
		100
		90
Recommended Cooling
	(Minutes)	80
		70
		60
		50
		40
		30
		20
		10
		0
		0	10	20	30	40	50	60	70	80	90
				Compressor Unloaded Run Time (Minutes)

*Times are approximate.

NOTE: Various factors, including high humidity, high ambient temperature, and the presence of a sound blanket will increase cool-down times.

*Times are approximate.

NOTE: Various factors, including high humidity, high ambient temperature, and the presence of a sound blanket will increase cool-down times.

Fig. 15 — Recommended Minimum Cool-Down Time

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.

Start Unit

Set the space thermostat to a set point above space temperature so that there is no demand for cooling. Close the 38 AUQ dis- connect switch. 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 low-pressure side of system. Do not overcharge. During charging or removal of refriger- ant, be sure indoor-fan system is operating. Ensure both outdoor fan motors are running; bypass any Motormaster function.

Adjust Refrigerant Charge

The unit must be charged in Cooling mode only. Refer to Cool- ing Charging Charts, Fig. 16 through Fig. 18. For applications with line lengths greater than 100 ft, contact Carrier representa- tive. Vary refrigerant until the conditions of the chart are met. 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.

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