Thermistor; Thermistor For Indoor Unit - Hitachi Utopia RPI-2.5HRG Service Manual

3.5

Thermistor

3.5.1 Thermistor for Indoor Unit

(1) Position of Thermistor (In Case of 4-Way Cassette Type)
Thermistor
for Air Outlet
Temperature
(THM2)
(2) Thermistor for Indoor Suction Air
Temperature (For Room Temperature
Control)
The room temperature is controlled by the
thermistor for indoor suction air
temperature detecting the temperature at
the suction air inlet of the indoor unit.
The setting temperature is indicated on the
L.C.D. of the remote control switch by
number.
Adjust the setting temperature for
prevention from excessive cooling and
heating.
It is recommended to set the temperature
as follows;
Economical Cooling Operation: 27
The resistance characteristics of thermistor is shown in the above figure.
ATTENTION:
The thermo-off value of the indoor unit air inlet thermistor is set at the temperature higher than the value
indicated on the remote control switch by 4
during heating operation has a tendency to become higher than that of the occupied zone, intending
comfortable heating operation.
(3) Thermistor for Indoor Discharge Air Temperature (For Discharge Air Temperature Control)
The thermistor for indoor discharge air temperature is utilized for the control of prevention from cold
air discharge in heating operation, etc.
The resistance characteristics of thermistor is shown in the above figure.
(4) Thermistor for Liquid Pipe Temperature of Indoor Heat Exchanger
When the temperature of the heat exchanger is below 0
thermostat is turned OFF automatically and over 14
thermostat is turned ON again.
The resistance characteristics of thermistor is shown in the above figure.
(5) Thermistor for Gas Pipe Temperature of Indoor Heat Exchanger
When the temperature of the heat exchanger is below 0
thermostat is turned OFF automatically and over 14
thermostat is turned ON again.
The evaporating temperature in heating operation is detected.
The resistance characteristics of thermistor is shown in the above figure.
Thermistor for
Air Inlet Temperature
(THM1)
Thermistor
Resistance
(KΩ)
o C to 29 o C / Economical Heating Operation: 18
o C and the maximum is 30
Thermistor for Indoor Heat Exchanger
Gas Pipe Temperature (THM5)
Thermistor for Indoor Heat
Exchanger Liquid Pipe
Temperature
(For Freeze Protection) (THM3)
90
82
80
70
61
60
50
46
40
35
30
27
20.5
20
16
10
0
-15 -10 -5 0 5 10 15 20
Ambient Temperature (
Thermistor Characteristics
o C, because the suction air temperature
o
C, Prevention from freezing
o
C, onto the heat exchanger in
COOL and DRY operation.
o
C,
Prevention from freezing
o
C,
onto the heat exchanger in
COOL and DRY operation.
MAIN PARTS
12.5
10
8
5.3
3.6
2.5
25 30 35 40 45 50 55 60
o
C)
o C to 20 o C
3-9