MXS Service Manual

Control Specification SiUS121736EA
109 Functions and Control
4.14 Malfunctions
4.14.1 Sensor Malfunction Detection
Sensor malfunction may occur either in the thermistor or current transformer (CT) system.
Relating to Thermistor Malfunction
1. Outdoor heat exchanger thermistor
2. Discharge pipe thermistor
3. Radiation fin thermistor
4. Gas pipe thermistor
5. Outdoor temperature thermistor
6. Liquid pipe thermistor
Relating to CT Malfunction
Refer to CT or related abnormality on page 201 for details.
4.14.2 Detection of Overcurrent and Overload
Outline In order to protect the inverter, an excessive output current is detected and the OL temperature is
observed to protect the compressor.
Details  If the inverter current exceeds 13.0 ~ 18.5 A (depending on the model), the system shuts down
the compressor.
 If the OL (compressor head) temperature exceeds 130°C (266°F), the compressor stops.
4.14.3 Refrigerant Shortage Control
Outline 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 comparing with that in the normal operation when refrigerant is
insufficient, and refrigerant shortage is detected by checking power consumption.
Refer to refrigerant shortage on page 179 for details.
4.14.4 Anti-Icing Function
During cooling, if the indoor heat exchanger temperature in the operation stopped room drops
below the specified temperature for a specified time, the electronic expansion valve is opened in
the operation stopped room as specified, and the fully closed operation is carried out. After this, if
freezing abnormality occurs longer than a specified time, the system is shut down.
Frequency
Refrigerant shortage zone
(R21927)
40 ~ 54 Hz
(depending on
the model)
Power consumption (Input current)