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