Daikin FTXZ25NV1B Service Manual page 71

SiMT041311E
2.11.7 Discharge Pipe Thermistor Disconnection Control
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 (360 seconds) finishes, the detection timer for disconnection of the
discharge pipe thermistor (720 seconds) starts. When the timer is over, the following adjustment
is made.
1. When the operation mode is cooling
2. When the operation mode is heating
When the thermistor is disconnected
When the disconnection is ascertained, the compressor continues operation for 9 minutes and
then stops.
When the compressor stops repeatedly, the system is shut down.
2.11.8 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 checked
every 20 seconds. The opening degree of the electronic expansion valve is adjusted by the
followings.
♦ Target discharge pipe temperature
♦ Actual discharge pipe temperature
♦ Previous discharge pipe temperature
Function and Control
When the following condition is fulfilled, the discharge pipe thermistor disconnection is
ascertained.
Discharge pipe temperature + 6°C < outdoor heat exchanger temperature
When the following condition is fulfilled, the discharge pipe thermistor disconnection is
ascertained.
Discharge pipe temperature + 6°C < indoor heat exchanger temperature
SC
(Subcool)
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)
56