SiUS12-928_B
Troubleshooting for Outdoor Unit
Service Diagnosis
156
6. Troubleshooting for Outdoor Unit
6.1
Refrigerant Shortage
Remote
Controller
Display
U0
Outdoor Unit LED
Display
A
5
1
3
2
3
3
4
4
4
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 outdoor 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.
<18 class>
Input current × input voltage
A
× output fre
B
Output frequency >
C
<24/32 class>
Input current
D
× output fre
E
Output frequency >
F
Refrigerant shortage detection II:
The following conditions continue for 80 seconds.
Opening of the outdoor electronic expansion valve
G
Discharge pipe temperature (°C) >
H
× target discharge pipe temperature (°C) +
J
(°C)
(Discharge pipe temperature (°F) >
H
× target discharge pipe temperature (°F) +
K
(°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 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 outdoor electronic expansion valve
A
(–)
B
(W)
C
(Hz)
1756/256
50
55
D
(–)
E
(A)
F
(Hz)
27/1000
2
40
G
(pulse)
H
(–)
J
(°C)
K
(°F)
450
255/256
cooling: 20, heating: 40
cooling: 36.1, heating: 72.1
