Daikin FTXG20LV1BW, Service Manual

Page: 76 / 128

Troubleshooting SiBE041401E
65 Service Diagnosis
4.7 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 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: (20/25/35 class only)
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.
Š
Input current × input voltage
≤
A × output fre B
Š
Output frequency > C
Refrigerant shortage detection II:
The following conditions continue for 80 seconds.
Š
Opening of the electronic expansion valve
≥
D
Š
Discharge pipe temperature > E × target discharge pipe tempe F
Refrigerant shortage detection III: (20/25/35 class only)
When the difference of the temperature is smaller than G °C, 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 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 electronic expansion valve
A
(constant)
B (W) C (Hz)
20/25/35 class 640/256 0 55
50 class 2000/256 –181 55
D (pulse) E (
constant
) F (°C)
20/25/35 class 480 128/128 30
50 class 480 128/128 cooling: 60, heating: 45
Operation
mode
Description G (°C)
Cooling
room thermistor temperature – indoor heat exchanger temperature 4.0
outdoor heat exchanger temperature – outdoor temperature 4.0
Heating
indoor heat exchanger temperature – room thermistor temperature 3.0
outdoor temperature – outdoor heat exchanger temperature 3.0