Hitachi FSG Series Service Manual page 182

3
MAIN PARTS
10
n Thermistor for Room Temperature Control (Indoor
Unit Air Inlet Temperature Thermistor, THM1)
The room temperature control is performed by this air inlet
temperature thermistor, THM1. The setting temperatures are
indicated on the remote control switch with figures. Set room
temperature so that room temperature does not become too
cool or too hot. We recommend that temperature be set in
the following ranges.
Economical Cooling Operation: 27°C to 29 °C
Economical Heating Operation: 18 °C to 20 °C
The resistance characteristics of the thermistor is shown in
Fig. 3. 4
Temperature (°C)
Fig. 3. 4 Resistance Characteristics of Thermistor for Air
Inlet Temperature
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CAUTION:
The thermo-off valve of the indoor unit air inlet
thermistor is set at the temperature higher than the
value indicated on the remote control switch by 4 °C
and the maximum is 34 °C, because suction air
temperature during heating operation has a tendency
to become higher than that of the occupied zone,
intending comfortable heating operation.
n Thermistor for Discharge Air Temperature Control
(Indoor Unit Discharge Air Temperature Thermistor,
THM2)
This thermistor (THM2) has been installed to prevent cold
blow during heating operation. The characteristics of the
thermistor resistance is shown in Fig. 3. 4
n Thermistor for Liquid Pipe of Indoor Heat Exchanger
When the temperature of the indoor heat exchanger
decreases to 0 °C or lower for 3 minutes, the thermostat is
automatically turned off. When the temperature increase to
16 °C or higher, the thermostat is turned on.
The purpose of this function is to prevent frosting on the heat
exchanger during cooling operation and dry operation.
The characteristics of the thermistor resistance is shown in
Fig. 3. 4
n Thermistor for Gas Pipe of Indoor Heat Exchanger
This thermistor senses the evaporating temperature during
heating operation. The characteristics of the thermistor
resistance is shown in Fig. 3. 4
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