SiBE121021_C Troubleshooting for Outdoor Unit
Service Diagnosis 357
7.16 Refrigerant Shortage
Remote
Controller
Display
U0
Outdoor Unit LED
Display
A
j
1
h
2
h
3
i
4
i
5
h
Method of
Malfunction
Detection
Refrigerant shortage detection I :
Refrigerant shortage is detected by checking the input current value and the compressor output
frequency. If the refrigerant is short, the input current is smaller than the normal value.
Refrigerant shortage detection II :
Refrigerant shortage is detected by checking the discharge pipe temperature and the opening of
the electronic expansion valve. If the refrigerant is short, the discharge pipe temperature tends
to rise.
Malfunction
Decision
Conditions
Refrigerant shortage detection I :
The following conditions continue for 7 minutes.

DC current
≤
A × Compressor output frequency + B

Output frequency > C
Refrigerant shortage detection II :
The following conditions continue for 80 seconds.

Opening of the electronic expansion valve
≥
D

Discharge pipe temperature > E × target discharge pipe temperature +F
îš„
If the error repeats 4 times, the system is shut down.
îš„
Reset condition: Continuous run for about 60 minutes without any other error
Supposed
Causes
îš„
Refrigerant shortage (refrigerant leakage)
îš„
Poor compression performance of compressor
îš„
Disconnection of the discharge pipe thermistor, indoor or outdoor heat exchanger thermistor,
room or outdoor temperature thermistor
îš„
Closed stop valve
îš„
Defective electronic expansion valve
A
(–)
B
(A)
C
(Hz)
50/52/58 class 0.01 0.3 54
68/75 class 0.035 0.5 55
80/90 class 0.027 2.0 40
D
(pulse)
E
(–)
F
(°C)
Cooling
450
255/256 20
Heating 255/256 40
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