Daikin Super Multi NX FFQ25B8V1B Service Manual page 136

Control Specification
4.12.8 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 (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 followings.
♦
♦
♦
4.12.9 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.
Detail Start Conditions
After finishing the starting control (about 660 ~ 810 seconds), all the electronic expansion
valve(s) in the operating room is/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.
124
SC
(Subcool)
Target discharge pipe temperature
Actual discharge pipe temperature
Previous discharge pipe temperature
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.
The target discharge pipe
temperature is set as to become the
aiming SH.
The inclination does not change
depending on the operating condition.
SH
(Superheat)
SiBE121021_C
(R14213)
Function and Control