SiUS12-928_B Control Specification
Function and Control 66
3.12.8 Control for Disconnection of the Discharge Pipe Thermistor
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
outdoor 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 Detect Disconnection
When the starting control (630 seconds) 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 + 10.8°F (6°C) < 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 + 10.8°F (6°C) < highest indoor heat exchanger temperature
Adjustment when the thermistor is disconnected
When the disconnection is ascertained, the compressor continues operation for 9 minutes and then
stops.
If the compressor stops repeatedly, the system is shut down.
3.12.9 Gas Pipe Isothermal Control During Cooling
When the units are operating in multiple rooms, the gas pipe temperature is detected and the
outdoor 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, open the outdoor
electronic expansion valve in that room
When the gas pipe temperature < the average gas pipe temperature, close the outdoor
electronic expansion valve in that room
The temperatures are monitored every 40 seconds.
3.12.10 SC (Subcooling) Control
Outline The liquid pipe temperature and the heat exchanger temperature are detected and the outdoor
electronic expansion valve opening is compensated so that the SC of each room becomes the
target SC.
When the actual SC is > target SC, open the outdoor electronic expansion valve of the room.
When the actual SC is < target SC, close the outdoor electronic expansion valve of the room.
Detail Start Conditions
After finishing the starting control (630 seconds), (all) the outdoor electronic expansion valve(s) for
the operating room is/are controlled.
Determine Outdoor Electronic Expansion Valve Opening
The outdoor electronic expansion valve opening is adjusted so that the temperature difference
between the maximum heat exchanger temperature of connected room and the liquid pipe
temperature thermistor becomes constant.
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