Name And Role Of Each Thermistor - Hitachi RAM-55QH5 Service Manual

Name
OH thermistor
DEF thermistor
Outdoor temperature
thermistor
Electric expansion valve
thermistor (NARROW PIPE 1)
Electric expansion valve
thermistor (NARROW PIPE 2)
* Electric expansion valve
thermistor (NARROW PIPE 3)
Electric expansion valve
thermistor (WIDE PIPE 1)
Electric expansion valve
thermistor (WIDE PIPE 2)
* Electric expansion valve
thermistor (WIDE PIPE 3)
Remark :
" " mark is for model RAM-65QH5 only.
*
Table 10-2 shows the correspondence between
the thermistor's resistance and the temperature.
They should be used as reference values. The
value, which you measure, may be slightly
difference from that in the table. It depends on
the instrument.
When you measure the resistance, pull out the
connector after turning off the power supply.
Pulling out the connector while the power supply
is turned on will cause troubles.
Table 10-1 Name and Role of each thermistor
Connector No Measuring Point
CN5 Compressor head
CN6 Heat exchanger
CN7 Outside temperature
CN8 Indoor unit 1 (NARROW PIPE)
Indoor unit 2 (NARROW PIPE)
Indoor unit 3 (NARROW PIPE)
CN9 Indoor unit 1 (WIDE PIPE)
Indoor unit 2 (WIDE PIPE)
Indoor unit 3 (WIDE PIPE)
Table 10-2 Correspondence between each thermistor's
resistance and temperature (reference value)
Electric expansion valve
thermistor
DEF thermistor
Outdoor temperature
thermistor
OH thermistor
– 91 –
Role
If the temperature of the compressor
rises abnormally (118˚C), the
compressor will be stopped. The
temperature is used to decide the
operation of the valve.
The thermistors decide the defrost
operation during heating combined
the data of the outside temperature
and its data.
Outdoor temperature is used to
decide the various operations of the
air conditioner.
The thermistors detect the
temperatures of the piping to the
indoor units. The temperatures are
used to decide how much the
expansion valve is opened.
Temperature Resistance
-15˚C 12.6kΩ
0˚C 6.1kΩ
25˚C 2.2kΩ
860Ω
50˚C
75˚C 400Ω
Temperature Resistance
-15˚C 12.6kΩ
0˚C 6.1kΩ
15˚C 3.2kΩ
2kΩ
30˚C
Temperature Resistance
25˚C 33.9kΩ
50˚C 10.8kΩ
75˚C 4.1kΩ
1.7kΩ
100˚C
105˚C 1.5kΩ
1kΩ
118˚C
Microcomputer
pin potential
1.0V
1.7V
3.0V
3.9V
4.4V
Potential
1.0V
1.7V
2.4V
3.1V
Potential
0.5V
1.3V
2.4V
3.4V
3.6V
3.9V