Carrier 38AUQ 16 Series, Installation, Start-Up And Service Instructions Manual

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18
Compressor Overload —
This overload interrupts power to the compressor when
either the current or internal motor winding temperature
becomes excessive, and automatically resets when the
internal temperature drops to a safe level. This overload
may require up to 60 minutes (or longer) to reset. If the
internal overload is suspected of being open, disconnect
the electrical power to the unit and check the circuit
through the overload with an ohmmeter or continuity
tester.
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 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 unloaded, the longer it must cool before
the bi-metal disk resets. See Fig. 15.
C10080
Fig. 14 -- Advanced Scroll Temperature
Protection Label
0
10
20
30
40
50
60
70
80
90
100
110
120
0 10 20 30 40 50 60 70 80 90
Compressor Unloaded Run Time (Minutes)
Recommended Cooling
T
ime
(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.
C10081
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 disconnect switch. Only the crankcase heater
will be energized.
Reset the space thermostat below ambient so that a call
for cooling is ensured.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage.
Never charger liquid into the low--pressure side of the
system. Do not overcharge. During charging or
removal of refrigerant, be sure indoor--fan system is
operating. Ensure both outdoor fan motors re running;
bypass any Motormaster function.
CAUTION
!
Adjust Refrigerant Charge —
The unit must be charged in Cooling mode only. Refer to
Cooling Charging Charts, Figs. 16 and 17. For
applications with line lengths greater than 100 ft, contact
Carrier representative. Vary refrigerant until the
conditions of the chart are met. The charts are based on
charging the units to the correct subcooling 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 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 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.
38A
U
Q