Service Manual

SiUS091133 Troubleshooting
Service Diagnosis 104
4.6 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.
Refrigerant shortage detection III:
Refrigerant shortage is detected by checking the difference between suction and discharge
temperature.
Malfunction
Decision
Conditions
Refrigerant shortage detection I:
The following conditions continue for 7 minutes.
<09/12 class>
 Input current × input voltage
 A × output frequency + B
 Output frequency > C
<15/18/24/30/36 class>
 Input current
 D × output frequency + E
 Output frequency > F
Refrigerant shortage detection II:
The following conditions continue for 80 seconds.
 Opening of the 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))
A
(–)
B (W) C (Hz)
09/12 class 640/256 0 55
D (–) E (A) F (Hz)
15/18 class 2000/256 –181 55
24/30/36 class 27/1000 2.0 40
G (pulse) H (–) J (°C) K (°F)
09/12 class 480 128/128 cooling: 63.5, heating: 30 cooling: 114.3, heating: 54
15/18 class 480 128/128 cooling: 60, heating: 45 cooling: 108, heating: 81
24 class 450 128/128 60 108
30/36 class 480 128/128 cooling: 50, heating: 45 cooling: 90, heating: 81