Temperature Detection Circuit - Hitachi RAF-25NH4 Service Manual

6. Temperature Detection Circuit

The outdoor unit (this model) provides with the outdoor temperature thermistor, DEF (defrost) thermistor, OH (overheat)
●
thermistor and electric expansion valve thermistor so that they detect the temperatures of the unit and control the system.
The circuit of the thermistors is shown as Fig. 6-1, and their roles and temperature measuring points are shown as Table 6-1.
●
The DEF thermistor, OH thermistor and electric expansion valve are for A cycle and B cycle respectively. The outdoor
temperature thermistor is common to A cycle and B cycle.
CN4A XA2P
(white)
OH thermistor A
CN5A XA2P
(blue)
DEF thermistor A
CN6A XA2P
(red)
Outdoor temperature
thermistor A
CN7A XA8P
(white)
Electric expansion valve thermistor
(thin pipe 1) A
Electric expansion valve thermistor
(thick pipe 1) A
Electric expansion valve thermistor
(thin pipe 2) A
Electric expansion valve thermistor
(thick pipe 2) A
CN4B XA2P
OH thermistor B
(yellow)
CN5B XA2P
(black)
DEF thermistor B
CN7B XA8P
(black)
Electric expansion valve thermistor
(thin pipe 1) B
Electric expansion valve thermistor
(thick pipe 1) B
Electric expansion valve thermistor
(thin pipe 2) B
Electric expansion valve thermistor
(thick pipe 2) B
C o n t r o l
Fig. 6-1 Temperature Detection Circuit
226
Micro computer
AX 6N00
Outdoor temperature
Selection
Micro computer
AX 6N00
Outdoor temperature
Selection