Daikin FTXM-K Series Service Manual page 54

Control Specification
Detail 1. Determine command frequency
2. Determine upper limit frequency
3. Determine lower limit frequency
4. Determine prohibited frequency
When starting the compressor, the frequency is initialized according to the ∆D value of the
Initial Frequency
indoor unit.
<∆D signal: Indoor Frequency Command>
The difference between the room thermistor temperature and the target temperature is taken as
the ∆D signal and is used for frequency command.
∗
OFF = Thermostat OFF
PI Control 1. P control
2. I control
3. Frequency control when other controls are functioning
4. Upper and lower limit of frequency by PI control
39
Command frequency is determined in the following order of priority.
1. Limiting defrost control time
2. Forced cooling
3. Indoor frequency command
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.
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.
There is a certain prohibited frequency such as a power supply frequency.
∆D
Temperature Temperature
difference signal
∗OFF
–2.0
–1.5 1
–1.0 2
–0.5 3
The ∆D value is calculated in each sampling time (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 control is carried out only when the frequency drops.
For controlling lower limit;
Frequency control 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
SiBE041434E
∆D
signal
C
D
E
F