Daikin FTK Series Service Manual page 52

DAMA-SM-21-001
3.12.9 High Discharge Pipe Temperature Control
When the compressor is operating, if the discharge pipe temperature exceeds a certain value,
the electronic expansion valve opens and the refrigerant runs to the low pressure side. This
procedure lowers the discharge pipe temperature by cooling the compressor with refrigerant.
3.12.9-1 Determine Zones
3.12.9-2 Process for Each Zone
Dropping zone: Open the current opening by +20 pulses every 30 seconds
Reset zone: Release control and shift to target discharge pipe temperature control
3.12.10 Discharge Pipe Thermistor Disconnection Control
Outline
The disconnection of the discharge pipe thermistor is detected by comparing the discharge pipe
temperature with the condensing 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.
Details
Determining thermistor disconnection
When the starting control (A seconds) finishes, the detection timer for disconnection of the
discharge pipe thermistor (B seconds) starts. When the timer is over, the following adjustment is
made.
When the following condition is fulfilled, the discharge pipe thermistor disconnection is
ascertained.
Functions and Control
09
A (°C) 100
B (°C) 98
09
A (°F) 212.0
B (°F) 208.4
12 18
100 101
98 99
12 18
212.0 213.8
208.4 210.2
Control Specification
24
101
99
24
213.8
210.2
47