SiUS122226E Control Specification
Part 4 Functions and Control 95
4. Control Specification
4.1 Thermistor Functions
R4003431
The illustration is for the 4-room models as representative and have 4 lines of indoor unit system
(A ~ D).
Each system has respective number of lines according to the specified number of the rooms.
(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) Gas Pipe
Thermistor
In cooling operation, the gas pipe thermistor is used for gas pipe isothermal control. The system
controls electronic expansion valve opening so that the gas pipe temperature in each room
becomes equal.
(5) Liquid Pipe
Thermistor
Liquid pipe thermistor is used to protect the compressor against liquid attack during cooling
operation.
Four way valve
Compressor
EVC
EVD
EVB
EVA
Expansion valve
DCBA
(3) Outdoor
Temperature
Thermistor
(2) Outdoor Heat
Exchanger
Thermistor
(1) Discharge Pipe
Thermistor
(4) Gas Pipe
Thermistor
(6) Indoor Heat
Exchanger
Thermistor
(7) Room
Temperature
Thermistor
(5) Liquid Pipe
Thermistor
Fusible plug
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