Daikin FTX20JV1B Service Manual page 51

SiBE041010EA
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:
for disconnection of the discharge pipe thermistor (
the following adjustment is made.
When the following condition is fulfilled, the discharge pipe thermistor disconnection is
ascertained.
<Cooling>
Discharge pipe temperature + 6°C < outdoor heat exchanger temperature
<Heating>
Discharge pipe temperature + 6°C < indoor heat exchanger temperature
A (seconds)
B (seconds)
C (seconds)
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.
Function and Control
10
120
720
SC
(Subcool)
Target discharge pipe temperature
Actual discharge pipe temperature
Previous discharge pipe temperature
seconds, heating: seconds) finishes, the detection timer
A B
seconds) starts. When the timer is over,
C
The target discharge pipe
temperature is set as to become
the aim SH.
The inclination does not change
depending on the operating condition.
SH
(Superheat)
Control Specification
(R18921)
40