Hitachi RAD-25NH7 Service Manual page 47

4. Room Temperature Thermistor Circuit
Fig. 4-1 shows the room temperature
G
thermistor circuit.
5V
Room
temperature
thermistor
R305
R301
A
0V
5. Heat exchanger temperature thermistor circuit
The circuit detects the indoor heat
G
exchanger temperature and controls
the following.
(1) Preheating.
(2) Low-temperature defrosting during
cooling and
operation.
(3) Detection of the reversing valve
non-operation or heat exchanger
temperature thermistor open.
The voltage at
heat exchanger temperature as shown
in Fig. 5-2.
Microcomputer
Room
62
temp. input
C302
0V
Fig. 4-1
5V
Heat exchanger
temperature thermistor
R306
R302
A
0V
Fig. 5-1
dehumidifying
depends on the
A
The voltage at
G
temperature as shown in Fig. 4-2.
5
4
3
2
1
0
0
Microcomputer
Heat
61
exchanger
C303 temperature
input
0V
5
4
3
2
1
0
0
-10
– 57 –
depends on the room
A
10 20 30
Fig. 4-2
10 20 30
Fig. 5-2
40
40