Hitachi RAD-25NH4 - Page 51

– 61 –
5. Room Temperature Thermistor Circuit
● Fig. 5-1 shows the room temperature
thermistor circuit.
5
4
3
2
1
0
010
Room temperature (˚C)
Fig. 5-2
20 30 40
0V
Room
temperature
thermistor
0V
5V
Fig. 5-1
62
A
R305
C302
Microcomputer
Room
temp. input
Voltage at
(V)
R301
0V
Heat exchanger
temperature thermistor
0V
5V
Fig. 6-1
61
A
R306
C303
Microcomputer
Heat
exchanger
temperature
input
R302
A
5
4
3
2
1
0
010
-10
Heat exchanger temperature (˚C)
Fig. 6-2
20 30 40
Voltage at
(V)A
6. Heat exchanger temperature thermistor circuit
● The voltage at depends on the room
temperature as shown in Fig. 5-2.
● The circuit detects the indoor heat
exchanger temperature and controls
the following.
(1) Preheating.
(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 temperature as shown
in Fig. 6-2.
A
A