Thermistor - Hitachi RCI-1.0FSR Service Manual

4 Control system

Thermistor

4.13 Thermistor
Check that the thermistors are connected to the PCB inlet
and, if not, connect them.
Use a multimeter to check that the thermistor resistances
are between 240 Ω and 840 kΩ. Otherwise, replace any
defective thermistors.
?
N O T E
This figure is applicable to the following thermistors:
1. Inlet Air Thermistor (THM1),
2. Liquid Pipe Thermistor (Freeze Protection) (THM3),
3. Gas Pipe Thermistor (THM5),
4. Outlet Air Thermistor (THM2)
• Thermistor for Indoor Inlet Air Temperature (For Room Temperature Control). The room temperature is controlled
by the thermistor for indoor inlet air temperature detecting the temperature at the suction air inlet of the indoor unit.
The setting temperature is indicated on the LCD of the wired controller by number. Adjust the setting temperature for
prevention from excessive cooling and heating.
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N O T E
The thermo-off temperature of the indoor unit inlet air thermistor is set higher than the temperature indicated on the wired controller by 4ºC
and the maximum is 30ºC, because the suction air temperature during the heating operation has a tendency to become higher than that
of the occupied zone, intending comfortable heating operation.
• Thermistor for Indoor Outlet Air Temperature (For Discharge Air Temperature Control). The thermistor for indoor outlet
air temperature is utilized for the prevention from of air discharge in heating operation, etc.
• Thermistor for Liquid Pipe Temperature of Indoor Heat Exchanger. To Prevent freezing of the heat exchanger in
COOL and DRY operation. When the temperature of the heat exchanger is below 0ºC, the thermostat is turned OFF
automatically and when it is over 14ºC, the thermostat is turned ON again.
• Thermistor for Gas Pipe Temperature of Indoor Heat Exchanger. To Prevent freezing of the heat exchanger in
COOL and DRY operation. When the temperature of the heat exchanger is below 0ºC, the thermostat is turned OFF
automatically and when it is over 14ºC, the thermostat is turned ON again. The evaporating temperature in heating
operation is detected.
92 SMGB0137 rev.0 - 05/2021
Thermistor
resistance
(KΩ)
Air temperature (ºC)
Thermistor characteristics