Daikin FTXS20K2V1B Service Manual page 36

Control Specification
Indoor Frequency Command (∆D signal)
The difference between the room thermistor temperature and the target temperature is taken as
the "∆D signal" and is used for frequency command.
∗Th OFF = Thermostat OFF
Frequency Initial Setting
<Outline>
When starting the compressor, the frequency is initialized according to the ∆D value and the Q
value of the indoor unit.
Q value: Indoor unit output determined from indoor unit volume, airflow rate and other factors.
PI Control (Determine Frequency Up / Down by ∆D Signal)
1. P control
2. I control
3. Frequency management when other controls are functioning
4. Upper and lower limit of frequency by PI control
26
∆D
Temperature Temperature
difference signal
∗Th
–2.0
OFF
–1.5 1
–1.0 2
–0.5 3
The ∆D value is calculated in each sampling time (15 ~ 20 seconds), and the frequency is
adjusted according to its difference from the frequency previously calculated.
If the operating frequency does not change for more than a certain fixed time, the frequency
is adjusted according to the ∆D value.
When the ∆D value is low, the frequency is lowered.
When the ∆D value is high, the frequency is increased.
When frequency is dropping;
Frequency management is carried out only when the frequency drops.
For limiting lower limit
Frequency management is carried out only when the frequency rises.
The frequency upper and lower limits are set according to the command of the indoor unit.
When the indoor or outdoor unit quiet operation command comes from the indoor unit, the
upper limit frequency is lower than the usual setting.
∆D
Temperature
difference signal difference
0 4
0.5 5
1.0 6
1.5 7
∆D
Temperature
signal difference
2.0 8 4.0
2.5 9 4.5
3.0 A 5.0
3.5 B 5.5
Function and Control
SiBE041134
∆D
signal
C
D
E
F