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Control Specification SiUS121827E
106 Part 4 Functions and Control
ΔD signal: Indoor frequency command
The difference between the room thermistor temperature and the target temperature is taken as the
ΔD value and is used for ΔD signal of frequency command.
Values depend on the type of indoor unit.
∗ OFF = Thermostat OFF
Initial Frequency When starting the compressor, or when conditions are varied due to a change of operating rooms,
the frequency must be initialized according to a total of the maximum ΔD value of each room and a
total Q value (ΣQ) of the operating room (the room in which the thermostat is set to ON).
PI Control 1. P control
MaxΔD value is calculated in each sampling time (15 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 maxΔD value.
When maxΔD value is low, the frequency is lowered.
When maxΔD value is high, the frequency is increased.
3. Frequency control when other controls are functioning
When frequency is dropping:
Frequency control is carried out only when the frequency drops.
For limiting lower limit:
Frequency control 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 total of S values. When the indoor
unit quiet operation commands come from all the rooms or when the outdoor unit quiet
operation commands come from all the rooms, the upper limit frequency is lower than the usual
setting.
Temperature
difference
ΔD
signal
Temperature
difference
ΔD
signal
Temperature
difference
ΔD
signal
Temperature
difference
ΔD
signal
–2.0°C (–3.6°F) ∗OFF 0°C (0°F) 4 2.0°C (3.6°F) 8 4.0°C (7.2°F) 12
–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) 13
–1.0°C (–1.8°F) 2 1.0°C (1.8°F) 6 3.0°C (5.4°F) 10 5.0°C (9.0°F) 14
–0.5°C (–0.9°F) 3 1.5°C (2.7°F) 7 3.5°C (6.3°F) 11 5.5°C (9.9°F) 15
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