Troubleshooting
SiMX042215E
62
Part 6 Service Diagnosis
4.6 Refrigerant Shortage
Error Code
U0
Method of Error
Detection
Refrigerant shortage detection I:
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.
Refrigerant shortage detection II:
(electronic expansion valve type model only)
Refrigerant shortage is detected by checking the discharge pipe temperature and the opening of
the electronic expansion valve. If there is insufficient refrigerant, the discharge pipe temperature
tends to rise.
Refrigerant shortage detection III:
Refrigerant shortage is detected by checking the difference between suction and discharge
temperature.
Error Decision
Conditions
Refrigerant shortage detection I:
The following conditions continue for 7 minutes.
Input current × input voltage
A
× output fre
B
Output frequency >
C
Refrigerant shortage detection II:
(electronic expansion valve type model only)
The following conditions continue for 80 seconds.
Opening of the electronic expansion valve
D
Discharge pipe temperature >
E
× target discharge pipe tempe
F
Refrigerant shortage detection III:
Refrigerant shortage is detected when the difference of the temperature is smaller than
G
°C
If the error repeats, the system is shut down.
Reset condition: Continuous run for about 60 minutes without any other error
A
(coefficient)
B
(W)
C
(Hz)
12 class
2048/256
–120
40
18 class
3015/256
–230
50
24 class
1002/256
40
54
D
(pulse)
E
(coefficient)
F
(°C)
12 class
470
128/128
6
18 class
470
128/128
21
24 class
510
128/128
20
G
(°C)
12 class
18 class
24 class
Room thermistor temperature
indoor heat
exchanger thermistor
3.5
N/A
4.0
Outdoor heat exchanger temperature
outdoor
temperature
3.5
N/A
4.0
