Hisense Hi-FLEXi S Series Technical, Installation, Maintenance page 277

Main Parts
3.3 Pressure Sensor
(1) High Pressure Control
The high pressure during heating operation is detected by a high pressure sensor, and compressor frequencies are
controlled by the proportional controlling method with operating capacity of indoor units (or PID Control for Compressor
Frequency) so that the high pressure is controlled in an appropriate range. The output of the high pressure sensor during
heating operation performs protective control; gas by-pass control.
Heating Operation
Proportional Control of
Compressor Frequency
with Operating Capacity
High
of Indoor Units
Pressure
Control
Protection Control (Gas
Bypass Control)
(2) Low Pressure Control
The suction pressure during cooling operation is detected by a low pressure sensor, and compressor frequencies are
controlled by the proportional controlling method with operating capacity of indoor units (or PID Control for Compressor
Frequency) so that the suction pressure is controlled in an appropriate range.
If the suction pressure is excessively low, the cooling can be insufficient and parts composing the refrigeration cycle can
be damaged. For this reason, if the output of the low pressure sensor indicates vacuum and the value is maintained for
12 minutes or longer, the compressor is stopped for the purpose of protection.
Cooling Operation
Proportional Control of
Compressor Frequency
with Operating Capacity
Low
of Indoor Units
Pressure
Control
Vacuum Prevention
Control
4.5
2.5
0.5
0
Pressure MPa (kgf/cm
Output Characteristics of High Pressure Sensor
4.5
2.5
0.5
(0.3)
(-0.1) 0
Pressure MPa (kgf/cm
Output Characteristics of Low Pressure Sensor
268
2.5
5.0
G)
2
1.0 2.0
G)
2