Service Manual
Table Of Contents
Thermistor Functions SiUS041829E
44 Part 4 Functions and Control
2. Thermistor Functions
(1) Discharge
Pipe Thermistor
The discharge pipe thermistor is used for controlling discharge pipe temperature. If the
discharge pipe temperature (used in place of the inner temperature of the compressor) rises
abnormally, the operating frequency becomes lower or the operation halts.
The discharge pipe thermistor is used for detecting disconnection of the discharge pipe
thermistor.
(2) Outdoor Heat
Exchanger
Thermistor
The outdoor heat exchanger thermistor is used for controlling the target discharge pipe
temperature. The system sets the target discharge pipe temperature according to the outdoor
and indoor heat exchanger temperature, and controls the electronic expansion valve opening so
that the target discharge pipe temperature can be obtained.
In cooling operation, the outdoor heat exchanger thermistor is used for detecting the
disconnection of the discharge pipe thermistor. When the discharge pipe temperature drops
below the outdoor heat exchanger temperature by more than a certain value, the discharge pipe
thermistor is judged as disconnected.
In cooling operation, the outdoor heat exchanger thermistor is used for high pressure protection.
(3) Outdoor
Temperature
Thermistor
The outdoor temperature thermistor detects the outdoor air temperature and is used for
refrigerant shortage detection, input current control, outdoor fan control, liquid compression
protection function, and so on.
(4) Indoor Heat
Exchanger
Thermistor
The indoor heat exchanger thermistor is used for controlling the target discharge pipe
temperature. The system sets the target discharge pipe temperature according to the outdoor
and indoor heat exchanger temperature, and controls the electronic expansion valve opening so
that the target discharge pipe temperature can be obtained.
In cooling operation, the indoor heat exchanger thermistor is used for freeze-up protection
control. If the indoor heat exchanger temperature drops abnormally, the operating frequency
becomes lower or the operation halts.
In heating operation, the indoor heat exchanger thermistor is used for detecting the
disconnection of the discharge pipe thermistor. When the discharge pipe temperature drops
below the indoor heat exchanger temperature by more than a certain value, the discharge pipe
thermistor is judged as disconnected.
(5) Room
Temperature
Thermistor
The room temperature thermistor detects the room air temperature and is used for controlling
the room air temperature.
Four way valve
Compressor
(R23851)
Expansion valve
(2) Outdoor Heat
Exchanger
Thermistor
(3) Outdoor
Temperature
Thermistor
(5) Room
Temperature
Thermistor
(1) Discharge Pipe
Thermistor
(4) Indoor Heat
Exchanger
Thermistor