3-25
MAIN PARTS
3.7
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.
(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 reaches 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 12
minutes or longer, the compressor is
stopped for the purpose of protection.
5
0.5
0.371
-0.1
(-1)
0
3.5
(35)
Output V
oltage
(DC V)
Pressure MPa (kgf/cm
2
G)
Heating Operation
Proportional Control of
Compressor Frequency
with Operating Capacity
of Indoor Units
Protection Control (Gas
Bypass Control)
Output Characteristics of High Pressure Sensor
High
Pressure
Control
4.36
0.5
0.37
-0.1
(-1)
0
3.0
(30)
Output V
oltage
(DC V)
Pressure MPa (kgf/cm
2
G)
Cooling Operation
Proportional Control of
Compressor Frequency
with Operating Capacity
of Indoor Units
Vacuum Prevention
Control
Output Characteristics of Low Pressure Sensor
Low
Pressure
Control
1.15
0.5
(5)
Heating Operation
PID Control for
Compressor Frequency
Protection Control
(Gas Bypass Control)
High
Pressure
Control
(FX Series Only)
Cooling Operation
PID Control for
Compressor Frequency
Vacuum Prevention
Control
Low
Pressure
Control
(FX Series Only)
