Hitachi RAS-07G4 - SENSOR AND THERMISTOR CIRCUITS; Room Temperature Sensing Circuit; Heat Exchanger Sensing Circuit

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8. Room Temperature Thermistor Circuit
● Fig. 8-1 shows the room temperature
thermistor circuit.
0V
Room
temperature
thermistor
0V
5V
Fig. 8-1
A
R309
C302
Micro
computer
(AX-3U)
Room
Thermistor
R310
0V
0V
Heat exchanger
temperature thermistor
0V
5V
Fig. 9-1
A
R307
C301
Micro computer
(AX-3U)
Hex
Thermistor
R308
R304
Q301
5
4
3
2
1
0
010
Room temperature (ßC)
Fig. 8-2
20 30 40
Voltage at
(V)A
5
4
3
2
1
0
010
-10
Heat exchanger temperature (ßC)
Fig. 9-2
20 30 40
Voltage at
(V)A
3
4
9. Heat exchanger temperature thermistor circuit
● The voltage at A depends on the room
temperature as shown in Fig. 8-2.
● The circuit detects the indoor heat
exchanger temperature and controls
the following.
(1) Low-temperature defrosting during
cooling and dehumidifying
operation.
The voltage at A depends on the heat
exchanger temperature as shown in
Fig. 9-2.