SiUS122226E Troubleshooting for Outdoor Unit
Part 6 Service Diagnosis 185
7. Troubleshooting for Outdoor Unit
7.1 Refrigerant Shortage
Error Code U0
Outdoor Unit LED
Display
A j 1 h 2 h 3 i 4 i 5 h
Method of Error
Detection
Refrigerant shortage is detected by checking the input current value and the compressor running
frequency. If there is insufficient refrigerant, the input current tends to be lower than the normal
value.
Error Decision
Conditions
The following conditions continue for 7 minutes.
Input current A × output frequency + B
Output frequency > C
Power consumption A × output frequency + B
Output frequency > C
If the error repeats, the system is shut down.
Reset condition: Continuous run for about 60 minutes without any other error
Supposed
Causes
The installation space not large enough
Dirty outdoor heat exchanger
Defective outdoor fan motor
Disconnection of the discharge pipe thermistor, indoor or outdoor heat exchanger thermistor,
room or outdoor temperature thermistor
Closed stop valve
Refrigerant shortage (refrigerant leakage)
Poor compression performance of compressor
Defective electronic expansion valve
2MXS 3/4MXS 2/3MXL(H)
A (coefficient) 10/1000 27/1000 27/1000
B (A) 0.3 2 2
C (Hz) 544040
5MXS 4MXL(H)
A (coefficient) 2230/256 2230/256
B (A) 50 50
C (Hz) 40 40
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