SiBE12-933_A
Control Specification
Function and Control
81
For Cooling Only Model
1. Determine command frequency
Command frequency is determined in the following order of priority.
1.1 Limiting frequency by drooping function
Input current, discharge pipes, freeze prevention, dew prevention, fin thermistor
temperature.
1.2 Indoor frequency command
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 prevention, 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 thermistor temperature and the target temperature is taken as
the “
∆
D signal” and is used for frequency command.
Values depend on the type of indoor unit
∗
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 (
Σ
Q) of the operating room (the room in which the thermostat is set
to ON).
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
A total of 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 is not change more than a certain fixed time, the frequency is
adjusted according to the
Σ∆
D value.
When the
Σ∆
D value is small...lower the frequency.
When the
Σ∆
D value is large...increase the frequency.
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
ex.)
Capacity
S value
2.5 kW
25
3.5 kW
35