Specifications

SiUS12-928_A Control Specification
Function and Control 46
Indoor Frequency Command (ΔD signal)
The difference between a room thermistor temperature and the target temperature is taken as the
“ΔD 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 ΔD 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, airflow rate and other factors.
PI Control (Determine Frequency Up / Down by ΔD Signal)
1. P control
A total of the ΔD 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 ΣΔD value.
When the ΣΔD value is small...lower the frequency.
When the ΣΔD value is large...increase the frequency.
3. Limit of frequency variation width
When the difference between input current and input current dropping 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 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.
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 in 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 from 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) ∗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
Capacity S value Capacity S value
9 kBtu 25 15 kBtu 50
12 kBtu 35 18 kBtu 60