Daikin FTXR-T Series, Service Manual

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Control Specification SiUS041829E
46 Part 4 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.
Details
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 control.
3. Determine lower limit frequency
The maximum value is set as an 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.
Initial Frequency
When starting the compressor, the frequency is initialized according to the

D value of the indoor
unit.

D signal: Indoor frequency command
The difference between the room thermistor temperature and the target temperature is taken as the

D value and is used for

D signal of frequency command.
Command freq u ency Limit frequency Skip control
Upper limit f u nction
Compressor protection f u nction
Lower limit f u nction
Fo u r way valve operation compensation, etc.
Target frequency
(R18023)
When the shift of the freq u ency is less than zero (
Δ
F<0) by PI control,
the target freq u ency is u sed as the command freq u ency.
Dropping f u nction
Inp u t c u rrent control, etc.
Upper limit frequency
FMAX
Lower limit frequency
FMIN
Initial freq u ency
PI control
Defrost control