Troubleshooting SiUS041111112 Service Diagnosis4.23 Refrigerant ShortageRemoteControllerDisplayU0Method ofMalfunctionDetectionRefrigerant shortage detection I:Refrigerant shortage is detected by checking the input current value and the compressor runningfrequency. 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 theelectronic 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 dischargetemperature.MalfunctionDecisionConditionsRefrigerant shortage detection I:The following conditions continue for 7 minutes. Input current × input voltage A × output frequency + B Output frequency > CRefrigerant shortage detection II:The following conditions continue for 80 seconds. Opening of the electronic expansion valve D Discharge pipe temperature (°C) > E × target discharge pipe temperature (°C) + F (°C)(Discharge pipe temperature (°F) > E × target discharge pipe temperature (°F) + G (°F))Refrigerant shortage detection III: (15/18/24 class only)When the difference of the temperature is smaller than H, it is regarded as refrigerant shortage. If the error repeats, the system is shut down. Reset condition: Continuous run for about 60 minutes without any other errorSupposedCauses Disconnection of discharge pipe thermistor, indoor or outdoor heat exchanger thermistor, roomor outdoor temperature thermistor Closed stop valve Refrigerant shortage (refrigerant leakage) Poor compression performance of compressor Defective electronic expansion valveA (–) B (W) C (Hz)09/12 class 777/256 –15 5015/18/24 class 2000/256 –181 54D (pulse) E (–) F (°C) G (°F)09/12 class Cooling 470 160/128 –1.5 –10.7Heating 172/128 –8.0 –25.415/18/24 class 470 128/128 20 36HCooling room thermistor temperature – indoor heat exchanger temperature 4.0°C (7.2°F)outdoor heat exchanger temperature – outdoor temperature 4.0°C (7.2°F)Heating indoor heat exchanger temperature – room thermistor temperature 4.0°C (7.2°F)outdoor temperature – outdoor heat exchanger temperature 4.0°C (7.2°F)
