SiBE12-933_A
Function of Thermistor
Function and Control
77
D Indoor Heat
Exchanger
Thermistor
1. The indoor heat exchanger thermistors are used for controlling target discharge pipe
temperature.
The system sets a 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.
2. The 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 halts.
3. The 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. The indoor heat exchanger thermistors are used for detecting disconnection of the discharge
pipe thermistor when heating.
When the discharge pipe temperature become lower than the maximum temperature of the
indoor heat exchanger temperature, the discharge pipe thermistor is judged as
disconnected.
The indoor heat exchanger thermistors are also used for preventing abnormal high pressure.
5. When only one indoor unit is operating, the indoor heat exchanger thermistor is used for
sub-cooling control.
The actual sub-cooling is calculated from the liquid pipe temperature and the heat
exchanger temperature. The system controls the electronic expansion valve opening to
reach the target sub-cooling.
E Liquid Pipe
Thermistor
1. When only one indoor unit is heating, the indoor liquid pipe thermistor is used for a sub-
cooling control.
The system calculates the actual sub-cooling with the liquid pipe temperature and the
maximum heat exchanger temperature between rooms, and controls the opening of the
electronic expansion valve to reach the target sub-cooling.
2. When all indoor units are heating, the liquid pipe thermistor is used for liquid pipes
isothermal control.
The system controls electronic expansion valve opening so that liguid pipe temperature in
each room becomes equal.