Daikin FTX20K2V1B, Service Manual

Page: 38 / 114

Control Specification SiBE041525F
27 Functions and Control
3.2 Frequency Control
Outline
The compressor frequency is determined according to the difference between the room
thermistor temperature and the target temperature.
Detail
1. Determine command frequency
Command frequency is determined in the following order of priority.
1. Limiting defrost control time
2. Forced cooling
3. Indoor frequency command
2. Determine upper limit frequency
The minimum value is set as an upper limit frequency among the frequency upper limits of
the following functions:
Compressor protection, input current, discharge pipe temperature, heating peak-cut, freeze-
up protection, defrost.
3. Determine lower limit frequency
The maximum value is set as a lower limit frequency among the frequency lower limits of the
following functions:
Four way valve operation compensation, draft prevention, pressure difference upkeep.
4. Determine prohibited frequency
There is a certain prohibited frequency such as a power supply frequency.
Command frequency Limit frequency
Skip control
Lower limit function
Four way valve operation compensation, etc.
Initial frequency
PI control
Defrost control
Dropping function
Input current control, etc.
Upper limit function
Compressor protection function
Upper limit frequency
FMAX
Lower limit frequency
FMIN
Target frequency
(R18023)
When the shift of the frequency is less than zero (
Δ
F<0) by PI control,
the target frequency is used as the command frequency.