Heat Exchanger Temperature Thermistor Circuit - Hitachi RAF-25NH4 Service Manual

5.Room Temperature Thermistor Circuit
Fig. 5-1 shows the room temperature
thermistor circuit.
5V
Room temperature
thermistor
R322
R321
A
0V

6.Heat exchanger temperature thermistor circuit

The circuit detects the indoor heat exchanger
temperature and controls the following.
(1) Preheation.
(2) Low-temperature defrosting during cooling
and dehumidifying operation.
(3) Detection of the reversing valve non-operation
or heat exchanger temperature thermistor open.
The voltage at depends on the heat exchanger
A
temperature as shown in Fig. 6-2
Micro
computer
Room
1
temp. input
C321
0V
Fig. 5-1
5V
Heat exchanger
temperature thermistor
R324
R323
A
0V
The Voltage at
temperature as shown in Fig. 5-2
5
4
3
2
1
0
Micro computer
64
Heat exchanger
C322
temperature input
0V
Fig. 6-1
5
4
3
2
1
0
-10
188
depends on the room
A
0 10 20
Room temperature(
Fig. 5-2
0 10 20
Room temperature(
℃
Fig. 6-2
30 40
)
℃
30 40
)