Si12-411A Function of Main Structural Parts
Function and Control 87
D Indoor Heat
Exchanger
Thermistor (DCN)
1. An indoor heat exchanger thermistor is used for controlling target discharge pipe
temperature.
Set a target discharge pipe temperature according to the outdoor and indoor heat exchanger
temperature.
Control the electronic expansion valve so that the target discharge pipe temperature can be
obtained.
2. An indoor heat exchanger thermistor is used to prevent freezing.
During the cooling operation, if the temperature drops abnormally, the operating frequency
becomes lower, then the operation must be halted.
3. An indoor heat exchanger thermistor is used for anti-icing control.
During the cooling operation, if the heat exchanger temperature in the room where operation
is halted becomes -1°C, or if the room temperature - heat exchanger temperature in the
room where operation is halted becomes ≥10°C, it is assumed as icing.
4. During heating: an indoor heat exchanger thermistor is used for detecting a disconnected
discharge pipe thermistor.
When a discharge pipe temperature become lower than an indoor heat exchanger
temperature, a disconnected discharge pipe thermistor can be detected.
5. An indoor heat exchanger thermistor is used for detecting incorrect wiring.
During the operation of checking incorrect wiring, refrigerant is passed in order from the port
A to detect a heat exchanger temperature, and then wiring and piping will be checked.
6. An indoor heat exchanger thermistor is used for sub-cooling control.
An actual sub-cooling must be calculated from an indoor liquid pipe temperature and a heat
exchanger temperature. The indoor heat exchanger thermistor controls the electronic
expansion valve opening to get a target sub-cooling.
7. An indoor heat exchanger thermistor is used for heating isothermal control of heat
exchanger.
When heating: if the difference in temperature of each room is greater than 8°C, the
electronic expansion valve of the room whose temperature is the higher is opened.
E Indoor Liquid
Pipe Thermistor
(DLN)
1. When heating: used for a sub-cooling control.
Calculate an actual sub-cooling from the temperature of indoor liquid pipes and a heat
exchanger temperature.
Actual sub-cooling
A maximum heat exchanger temperature in each room - adjust the opening of the electronic
expansion valve so that the liquid pipe temperature of each room becomes an target sub-
cooling.
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