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SiUS091133 Control Specification
Function and Control 44
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.
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
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.
2. I control
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.
3. Frequency management when other controls are functioning
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.
4. Upper and lower limit of frequency by PI control
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.
Temperature
difference
D
signal
Temperature
difference
D
signal
Temperature
difference
D
signal
Temperature
difference
D
signal
–2.0°C (–3.6°F) Th
OFF
0°C (0°F) 4 2.0°C (3.6°F) 8 4.0°C (7.2°F) C
–1.5°C (–2.7°F) 1 0.5°C (0.9°F) 5 2.5°C (4.5°F) 9 4.5°C (8.1°F) D
–1.0°C (–1.8°F) 2 1.0°C (1.8°F) 6 3.0°C (5.4°F) A 5.0°C (9°F) E
–0.5°C (–0.9°F) 3 1.5°C (2.7°F) 7 3.5°C (6.3°F) B 5.5°C (9.9°F) F
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