Control Specification (15/18/24 Class) SiUS04-904
50 Function and Control
4.2 Frequency Control
Outline Frequency is determined according to the difference between room and set temperature.
The function is explained as follows.
1. How to determine frequency.
2. Frequency command from an indoor unit. (The difference between a room temperature and the
temperature set by the remote controller.)
3. Frequency command from an indoor unit.
4. Frequency initial setting.
5. PI control.
Detail How to Determine Frequency
The compressor’s frequency is determined by taking the following steps.
For Heat Pump Model
1. Determine command frequency
Command frequency is determined in the following order of priority.
1.1 Limiting defrost control time
1.2 Forced cooling
1.3 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 pipe temperature, low Hz high pressure,
heating peak-cut, freeze-up protection, defrost.
3. Determine lower limit frequency
Set a maximum value 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.
Command frequency
Limit frequency
Skip control
Upper limit function
Compressor protection function
Lower limit function
Four-way valve operating compensation, etc. (*)
Initial frequency
PI control
Defrost control (*)
Dropping function
Input current control, etc.
Upper limit frequency
Lower limit frequency
FMIN
Target frequency
Command frequency X repeats when frequency becomes lower
Frequency changes by PI control < repeats when frequency becomes lower
*; only for heat pump model
(R2831)
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