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Control Specification SiUS091133
53 Function and Control
3.11.7 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 condensation 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 When the starting control (cooling: A seconds, heating: B seconds) finishes, the detection timer for
disconnection of the discharge pipe thermistor (
C seconds) starts. When the timer is over, 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) < 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.
3.11.8 Target Discharge Pipe Temperature Control
The target discharge pipe temperature is obtained from the indoor and outdoor heat exchanger
temperature, and the electronic expansion valve opening is adjusted so that the actual discharge
pipe temperature becomes close to the target discharge pipe 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 the followings.
Target discharge pipe temperature
Actual discharge pipe temperature
Previous discharge pipe temperature
09/12 class 15/18/24 class 30/36 class
A (seconds) 10 10 30
B (seconds) 120 30 30
C (seconds) 810 540 540
SC
(Subcool)
SH
(Superheat)
The target discharge pipe
temperature is set as to become the
aiming SH.
The inclination does not change
depending on the operating condition.
(R14213)
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