SiUS04-904 Control Specification (15/18/24 Class)
Function and Control 59
4.12.7 Control when frequency is changed
When the target discharge pipe temperature control is active, if the target frequency is changed for
a specified value in a certain time period, cancel the target discharge pipe temperature control and
change the target opening of the electronic expansion valve according to the shift.
4.12.8 Target Discharge Pipe Temperature Control
Obtain the target discharge pipe temperature from the indoor and outdoor heat exchanger
temperature, and adjust the electronic expansion valve opening so that the actual discharge pipe
temperature becomes close to that temperature. (Indirect SH (superheating) control using the
discharge pipe temperature)
The electronic expansion valve opening and the target discharge pipe temperature are adjusted
every 20 seconds. The target discharge pipe temperature is controlled by indoor heat exchanger
temperature and outdoor heat exchanger temperature. The opening degree of the electronic
expansion valve is controlled by following:
®The target discharge pipe temperature
®The actual discharge pipe temperature
®The previous discharge pipe temperature
4.13 Malfunctions
4.13.1 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. Fin thermistor
4. Outside air thermistor
Relating to CT Malfunction
When the output frequency is more than 55 Hz and the input current is less than 1.25A, carry out
abnormal adjustment.
4.13.2 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 248~266°F (120~130°C) (depending on
the model), the compressor gets interrupted.
If the inverter current exceeds 30 A, the system shuts down the compressor.
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