Daikin CTXU25G2V1B Service Manual page 29

Function of Thermistor
D Indoor Heat 1. The indoor heat exchanger thermistors are used for controlling target discharge temperature.
Exchanger
Thermistor
2. The indoor heat exchanger thermistor is used to prevent freezing.
3. The indoor heat exchanger thermistor is used for anti-icing control.
4. The indoor heat exchanger thermistor is used to heating peak-cut control.
5. During heating: the indoor heat exchanger thermistors are used for detecting disconnection
6. When only one indoor unit is operating, the indoor heat exchanger thermistor is used for
E Liquid Pipe 1. When only one indoor unit is heating, the indoor liquid pipe thermistor is used for a sub-
Thermistor
2. When all indoor units are heating, the liquid pipe thermistor is used for liquid pipes
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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.
During the cooling operation, if the temperature drops abnormally, the operating frequency
becomes lower, then the operation halts.
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.
During heating operation, if the temperature rises abnormally, the operating frequency
becomes lower, then the operation halts.
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.
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.
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.
isothermal control.
The system controls electronic expansion valves to make liquid pipe temperatures the
average of present temperature of each room.
SiBE12-908
Function and Control