Service Manual

SiUS121502E Control Specification
Function and Control 75
3.13.8 Discharge Pipe Thermistor Disconnection Control
Outline The disconnection of the discharge pipe thermistor is detected by comparing the discharge pipe
temperature with the condensing temperature. If the discharge pipe thermistor is disconnected, the
electronic expansion valve opens according to the outdoor temperature and the operation
frequency, operates for a specified time, and then stops.
After 3 minutes, the operation restarts and checks if the discharge pipe thermistor is disconnected.
If the discharge pipe thermistor is disconnected, the system stops after operating for a specified
time.
If the disconnection is detected repeatedly, the system is shut down. When the compressor runs for
60 minutes without any error, the error counter is reset.
Detail Determining thermistor disconnection
When the starting control (660 ~ 690 seconds, depending on the model) finishes, the following
adjustment is made.
1. When the operation mode is cooling
When the following condition is fulfilled, the discharge pipe thermistor disconnection is
ascertained.
Discharge pipe temperature + 6°C (10.8°F) < outdoor heat exchanger temperature
2. When the operation mode is heating
When the following condition is fulfilled, the discharge pipe thermistor disconnection is
ascertained.
Discharge pipe temperature + 6°C (10.8°F) < highest indoor heat exchanger temperature
When the thermistor is disconnected
When the disconnection is ascertained, the compressor continues operation for 9 minutes and then
stops.
3.13.9 Gas Pipe Isothermal Control During Cooling
When the units are operating in multiple rooms, the gas pipe temperature is detected and the
electronic expansion valve opening is adjusted so that the temperature of the gas pipe in each
room becomes equal.

When the gas pipe temperature > the average gas pipe temperature,
→ the opening degree of electronic expansion valve in the corresponding room increases.

When the gas pipe temperature < the average gas pipe temperature,
→ the opening degree of electronic expansion valve in the corresponding room decreases.
The temperatures are monitored every 40 seconds.