Daikin FTKD50BVM, Service Manual

Page: 55 / 210

Function of Main Structural Parts Si04-306
46 Function and Control
2. Function of Main Structural Parts
2.1 Function of Thermistor
2.1.1 Heat Pump Model
A Outdoor Heat
Exchanger
Thermistor
(DCB)
1. The outdoor heat exchanger thermistor is used for controlling target discharge temperature.
Set a target discharge temperature depending on the outdoor and indoor heat exchanger
temperature.
Control the electronic expansion valve opening so that the target discharge temperature can
be obtained.
2. The outdoor heat exchanger thermistor is used for detecting the discharge thermistor
disconnected when cooling.
When the temperature of the discharge piping is lower than the temperature of outdoor heat
exchanger, a disconnected discharge thermistor can be detected.
3. The outdoor heat exchanger thermistor is used for high pressure protection during cooling
operation.
B Discharge
Pipe Thermistor
(DOT)
1. The discharge pipe thermistor is used to control the discharge pipe.
If the temperature of discharge pipe (used in place of the inner temperature of the
compressor) rises abnormally, the operating frequency drops or the operation must be
halted.
2. The discharge pipe thermistor is used for detecting the discharge thermistor disconnected.
C Indoor Heat
Exchanger
Thermistor
(DCN)
1. The 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. 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 must be halted.
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. During heating: the indoor heat exchanger thermistor is used for detecting the discharge
pipe thermistor disconnected.
When the discharge pipe temperature become lower than an indoor heat exchanger
temperature, a disconnected discharge pipe thermistor can be detected.
Four way valve
Compressor
(R2827)
A
C
B
Electrontic
expansion valve