21
ADVANCED SCROLL TEMPERATURE PROTECTION
(ASTP)
A label located above the terminal box identifies Copeland
1
Scroll compressor models that contain this technology. See
Fig. 20. 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 149°C (300°F). At this temperature, an internal bi-
metal disk valve opens and causes the scroll elements to sepa-
rate, which stops compression. Suction and discharge pressures
balance while the motor continues to run. The longer the com-
pressor runs unloaded, the longer it must cool before the bi-met-
al disk resets. See Fig. 21.
To manually reset ASTP, the compressor should be stopped
and allowed to cool. If the compressor is not stopped, the mo-
tor 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.
Fig. 20 — Advanced Scroll Temperature Protection Label
Fig. 21 — Recommended Minimum Cool-Down Time After
Compressor is Stopped
Start Unit
Set the space thermostat to a set point above space temperature
so that there is no demand for cooling. Close the 569J discon-
nect switch. Only the crankcase heater will be energized.
Reset the space thermostat below ambient so that a call for
cooling is ensured.
ADJUST REFRIGERANT CHARGE
Refer to Cooling Charging Charts, Fig. 22-29. 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 subcooling for the
various operating conditions. Accurate pressure gage and tem-
perature 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 outdoor ambient
temperature does not affect the reading. Indoor airflow must be
within the unit’s normal operating range. Operate the unit for a
minimum of 15 minutes. Ensure that pressure and temperature
readings have stabilized. Plot the liquid pressure and tempera-
ture on chart and add or reduce the charge to meet the curve.
see Table 18. Adjust the charge to conform with the charging
chart, using the liquid pressure and temperature to read the
chart.
Table 18 — Using Plotted Operating Point
FINAL CHECKS
Ensure that all safety controls are operating, control panel cov-
ers are on, and the service panels are in place.
1. Copeland is a trademark of Emerson Climate Technologies.
0
10
20
30
40
50
60
70
80
90
100
110
120
0
10
20
30
40
60
70
80
90
50
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.
Recommended Cooling
T
ime*
(Minutes)
CAUTION
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage.
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.
IF PLOTTED OPERATING
CONDITION IS
ADJUST CHARGE BY
BELOW the curve
REDUCE charge
ABOVE the curve
ADD charge
