High Pressure Protection; Discharge Pipe Temperature Control - Daikin FTXN25L Service Manual

Algorithm & Control

2.19 High Pressure Protection

To prevent high pressure in the system.
Compressor operating frequency is adjusted based on upper limit of coil temperature.
Upper Limit Coil
Temperature
64°C
A
The compressor frequency is adjusted based on coil temperature:
• During cooling mode : outdoor coil temperature.
• During heating mode : indoor coil temperature.
This protection is activated when the coil temperature > 64°C, the compressor stops and outdoor fan stops
after 30s.The unit can only be restarted after 3 minutes.

2.20 Discharge Pipe Temperature Control

Used as a measure of the compressor's internal temperature.
Compressor frequency is control to keep this temperature from going up further when it rises above a certain
level.
Discharge temperature
110°C
102°C
If compressor discharge temperature > 102°C for the first time, this control starts and sets the current
frequency as upper limit. At the same time, running frequency starts to reduce by 1 step and so on, until
temperature falls between 99°C and 90°C at the keep zone.
This protection is activated when the compressor discharge temperature > 110°C. The compressor will stop
and considered trip.
If the compressor discharge temperature < 90°C , the compressor frequency will be reset based on the
outdoor ambient, set and room temperature.
27
B C
Stop zone
Drop zone
Frequency
keep zone
Reset zone
Compressor frequency
99°C
90°C