Daikin SUPER MULTI NX G Series Service Manual page 65

SiUS12-928_A
3.12.8 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 (superheat)
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
3.12.9 SC (Subcooling) Control
Outline
The liquid pipe temperature and the heat exchanger temperature are detected and the 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 electronic expansion valve of the room.
 When the actual SC is < target SC, close the electronic expansion valve of the room.
Detail
Start Conditions
When the starting control (630 seconds) finishes, all of the electronic expansion valve(s) in the
operating room are controlled.
Determine Electronic Expansion Valve Opening
The 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.
3.12.10 Disconnection of the Discharge Pipe Thermistor
Outline
A 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 operating
frequency, operates for a specified time, and then stops.
After 3 minutes of waiting, the operation restarts. Check 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 4 times in succession, then the system is shut down. When the
compressor runs for 60 minutes without any error, the error counter is reset.
Function and Control
SC
(Subcool)
SH
(Superheat)
Set the target discharge pipe
temperature to control SH.
The inclination does not change
depending on the operating condition.
Control Specification
56