Hitachi RAS-20CNHZ2 - Page 60

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5. Room Temperature Thermistor Circuit
● Fig. 5-1 shows the room temperature
thermistor circuit.
5
4
3
2
1
0
010
Room temperature (ßC)
Fig. 5-2
20 30 40
0V
Room
temperature
thermistor
0V
5V
Fig. 5-1
A
R309
C301
Micro
computer
AX-7M12
Room
temp. input
Voltage at
(V)
R310
0V
Heat exchanger
temperature thermistor
0V
5V
Fig. 6-1
A
R307
C302
Micro computer
AX-7M12
Heat
exchanger
temperature
input
R308
A
5
4
3
2
1
0
010
-10
Heat exchanger temperature (ßC)
Fig. 6-2
20 30 40
Voltage at
(V)A
1
64
6. Heat exchanger temperature thermistor circuit
● The voltage at A 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 A depends on the heat
exchanger temperature as shown in
Fig. 6-2.