Service manual

SiBE041102_A Troubleshooting
Service Diagnosis 83
4.22 Refrigerant Shortage
Remote
Controller
Display
U0
Method of
Malfunction
Detection
Refrigerant shortage detection I:
Refrigerant shortage is detected by checking the input current value and the compressor
running frequency. If the refrigerant is short, the input current is lower 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.

Input current × input voltage
≤
A × 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

If the error repeats, the system is shut down.

Reset condition: Continuous run for about 60 minutes without any other error
Supposed
Causes

Disconnection of 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
A (–)
B
(W)
C
(Hz)
1600/256 –160 46
D
(pulse) E
(–) F
(°C)
25 class
Cooling
470
190/128 –7
Heating 211/128 –11
35 class
Cooling
470
160/128 –1.5
Heating 172/128 –8