Carrier WEATHERMAKER 48/50AJ Operation And Service Manual page 79

COMPRESSOR RUNNING BUT COOLING INSUFFICIENT
Suction Pressure Low
1. Refrigerant charge low.
2. Head pressure low.
3. Air filters dirty.
4. Expansion valve power head defective.
5. Indoor coil partially iced.
6. Indoor airflow restricted.
Suction Pressure High
Heat load excessive.
UNIT OPERATES TOO LONG OR CONTINUOUSLY
1. Low refrigerant charge.
2. Control contacts fused.
3. Air in system.
4. Partially plugged expansion valve or filter drier.
SYSTEM IS NOISY
1. Piping vibration.
2. Compressor noisy.
COMPRESSOR LOSES OIL
1. Leak in system.
2. Crankcase heaters not energized during shutdown.
FROSTED SUCTION LINE
Expansion valve admitting excess refrigerant.
HOT LIQUID LINE
1. Shortage of refrigerant due to leak.
2. Expansion valve opens too wide.
FROSTED LIQUID LINE
Restricted filter drier.
INDOOR FAN CONTACTOR OPEN
1. Power off.
2. Fuses blown in field power circuit.
3. No control power.
INDOOR FAN CONTACTOR CLOSED
1. VFD overload function tripped.
2. Motor leads loose.
3. Motor windings open.
4. Single phasing.
5. Belts broken or thrown.
6. Circuit breaker tripped.
LEGEND
ASTP — Advanced Scroll Temperature Protection
VFD — Variable Frequency Drive
Table 94 — Cooling Service Analysis (cont)
PROBLEM
1. Add refrigerant.
2. Check refrigerant charge.
3. Clean or replace filters.
4. Replace power head.
5. Check low-pressure setting.
6. Remove obstruction.
Check for open doors or windows.
1. Add refrigerant
2. Replace control.
3. Purge and evacuate system.
4. Clean or replace.
1. Support piping as required.
2. Replace compressor.
1. Repair leak.
2. Check wiring and relays. Check heater and replace if defective.
Adjust expansion valve.
1. Repair leak and recharge.
2. Adjust expansion valve.
Remove restriction or replace.
1. Restore power.
2. After finding cause and correcting, replace with correct fuses.
3. Check secondary fuses. Replace with correct type and size.
Replace transformer if primary windings are receiving power.
1. Refer to separate VFD technical manual for troubleshooting
instructions.
2. Check connections at motor lead junction box.
3. Check motor windings.
4. Check for blown fuse. Check for loose connections at motor
junction box.
5. Check belts. Replace as complete set if necessary.
6. Check for excessive current draw. Reset breaker. Replace if
defective.
79
SOLUTION