Service Manual

Control Specification SiUS041638E
35 Functions and Control
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.
∗OFF = Thermostat OFF
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For heating operation only.
PI Control 1. P control
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.
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 ∆D value is low, the frequency is lowered.
When ∆D value is high, the frequency is increased.
3. Frequency control when other controls are functioning
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When frequency is dropping:
Frequency control is carried out only when the frequency drops.
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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 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
–2.0°C (–3.6°F) ∗OFF 0°C (0°F) 4 2.0°C (3.6°F) 8
–1.5°C (–2.7°F) 1 0.5°C (0.9°F) 5 2.5°C (4.5°F) 9
–1.0°C (–1.8°F) 2 1.0°C (1.8°F) 6 3.0°C (5.4°F) 10
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–0.5°C (–0.9°F) 3 1.5°C (2.7°F) 7 3.5°C (6.3°F) 11
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