SiUS04-904 Control Specification (09/12 Class)
Function and Control 47
3.12 Malfunctions
3.12.1 Sensor Malfunction Detection
Sensor malfunction may occur in the thermistor.
Relating to Thermistor Malfunction
1. Outdoor heat exchanger thermistor
2. Discharge pipe thermistor
3. Fin thermistor
4. Outdoor air thermistor
3.12.2 Detection of Overload and Overcurrent
Outline In order to protect the inverter, detect an excessive output current, and for protecting compressor,
monitor the OL operation.
Detail If the OL (compressor head) temperature exceeds 248°F / 120°C (depending on the
model), the compressor is interrupted.
If the inverter current exceeds 22 A, the system shuts down the compressor.
3.12.3 Refrigerant Shortage Control
Outline There are three ways of control to detect refrigerant shortage.
I Detecting by power consumption
If the power consumption is below the specified value and the frequency is higher than the
specified frequency, it is regarded as refrigerant shortage.
The power consumption is low compared to the normal operation when refrigerant is insufficient,
and refrigerant shortage is detected by checking a power consumption.
II Detecting by discharge pipe temperature
If the discharge pipe temperature is higher than the target discharge pipe temperature, and the
electronic expansion valve is fully open (450 pulses) more than the specified time, it is regarded as
refrigerant shortage.
III Detecting by the difference of temperature
If the difference between inhale and exhale temperature is smaller than the specified value, it is
regarded as refrigerant shortage.
Refer to “Refrigerant Shortage” on page 138 for detail.
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