Daikin FTKM18PVMK, Service Manual

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Control Specification SiMT041509E
43 Function and Control
3.12 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 Determining thermistor disconnection
When the starting control finishes, the detection timer for disconnection of the discharge pipe
thermistor (
540
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 tempe 6°C < 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 tempe 6°C < indoor heat exchanger temperature
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.
3.13 Malfunctions
3.13.1 Sensor Malfunction Detection
Sensor malfunction can be detected in the following thermistor:
1. Outdoor heat exchanger thermistor
2. Discharge pipe thermistor
3. Radiation fin thermistor
4. Outdoor temperature thermistor
3.13.2 Detection of Overcurrent and Overload
Outline An excessive output current is detected and the OL temperature is observed to protect the
compressor.
Detail
„
If the OL (compressor head) temperature exceeds 130°C, the system shuts down the
compressor.
„
If the inverter current exceeds 18.0 A, the system shuts down the compressor.