Function of Thermistor
SiBE12-908
26
Function and Control
D
Indoor Heat
Exchanger
Thermistor
1. The indoor heat exchanger thermistors are used for controlling target discharge 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 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 thermistor is used to heating peak-cut control.
During heating operation, if the temperature rises abnormally, the operating frequency
becomes lower, then the operation halts.
5. During heating: the indoor heat exchanger thermistors are used for detecting disconnection
of the discharge pipe thermistor.
When the discharge pipe temperature become lower than an indoor heat exchanger
temperature, a disconnected discharge pipe thermistor can be detected.
The indoor heat exchanger thermistors are also used for preventing abnormal high pressure.
6. 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 valves to make liquid pipe temperatures the
average of present temperature of each room.