Control Specification Si12-411A
92 Function and Control
2. Determine upper limit frequency
Set a minimum value as an upper limit frequency among the frequency upper limits of the
following functions:
Compressor protection, input current, discharge pipes, freeze-up protection, dew prevention,
fin thermistor temperature.
3. Determine lower limit frequency
Set a maximum value as an lower limit frequency among the frequency lower limits of the
following functions:
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 a room temperature and the temperature set by the remote controller
will be taken as the “∆D signal” and is used for frequency command.
∗Th OFF = Thermostat OFF
Indoor Unit Capacity (S value)
The capacity of the indoor unit is a “S” value and is used for frequency command.
Frequency Initial Setting
<Outline>
When starting the compressor, or when conditions are varied due to the change of the operating
room, the frequency must be initialized according to the total of a maximum ∆D value of each
room and a total value of Q (ΣQ) of the operating room (the room in which the thermos is set to
ON).
Q value: Indoor unit output determined from indoor unit volume, air flow rate and other factors.
PI Control (Determine Frequency Up / Down by ∆D Signal)
1. P control
Calculate a total of the ∆D value in each sampling time (20 seconds), and adjust the
frequency according to its difference from the frequency previously calculated.
2. I control
If the operating frequency is not change more than a certain fixed time, adjust the frequency
up and down according to the Σ∆D value, obtaining the fixed Σ∆D value.
When the Σ∆D value is small...lower the frequency.
When the Σ∆D value is large...increase the frequency.
3. Limit of frequency variation width
When the difference between input current and input current drooping value is less than 1.5
A, the frequency increase width must be limited.
4. Frequency management when other controls are functioning
When each frequency is drooping;
Frequency management is carried out only when the frequency droops.
For limiting lower limit
Frequency management is carried out only when the frequency rises.
5. Upper and lower limit of frequency by PI control
The frequency upper and lower limits are set depending on the total of S values of a room.
When low noise commands come from the indoor unit more than one room or when outdoor
unit low noise or quiet commands come from all the rooms, the upper limit frequency must
be lowered than the usual setting.
Temperature
difference
∆D
signal
Temperature
difference
∆D
signal
Temperature
difference
∆D
signal
Temperature
difference
∆D
signal
0 ∗Th
OFF
2.0 4 4.0 8 6.0 C
0.5 1 2.5 5 4.5 9 6.5 D
1.0 2 3.0 6 5.0 A 7.0 E
1.5 3 3.5 7 5.5 B 7.5 F
Capacity S value Capacity S value
2.5 kW 25 5.0 kW 50
3.5 kW 35 6.0 kW 60
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