Werbung
10. Temperature Detection Circuit
HIC
+5V
O.H. thermistor
Ni
12.7V
lormal
2 . 7 V
or less
oe
a heat-2.7V or more
eset 2.3V or less
,
oe
_
i,
O.H.
CN4
oF
°
R512
+5V
Micro
computer
(AX-800)
DEF. thermistor
OV
ov
Normal 2.4V or more
may
Lod
Smell
Defrost 2.4V or less
al
4}
Reset 2.9V or more
(O74
.
CN5
R513
Outdoor temperature +5V
i
thermistor
OV
OV
On
Refer to the table 10-1.
Guidocy
CN7
YY
temperature
R514
iT
OV
OV
Fig. 10-1
@ The Over heat thermistor circuit detects the temperature at the surface of the compressor head, the Defrost. thermistor
circuit detects the defrosting operation temperature.
e A thermistor is a negative resistor element which has the characteristics that the higher (lower) the temperature, the
lower (higher) the resistance.
@ When the compressor is heated, the resistance of the Over heat thermistor becomes low and@)5V is divided by the
over heat thermistor and R512 and the voltage at pin 62 of microcomputer.
@ Microcomputer the voltage at pin 62 and the set value stored inside, and when it exceeds the set value, the micro
computer judges that the compressor is overheated and stops operation.
@ When frost forms on the outdoor heat exchanger, the temperature at the exchanger drops abruptly.
Therefore the resistance of the Defrost. thermistor becomes high and the voltage at pin 63 of microcomputer drops.
If this voltage becomes lower than the set value stored inside, the micro computer starts defrosting control.
®@ During defrosting operation the micro computer transfers the defrosting condition command to the indoor micro
computer via the SDO pin IF transfer output of the interface.
@ The microcomputer always reads the outdoor temperature via a thermistor (microcomputer pin 6 voltage), and
transfers it to the indoor unit, thus controlling the compressor rotation speed according to the value set at the EEPROM
in the indoor unit, and switching the operation status (outdoor fan on/off, etc.) in the dry mode.
The following shows the typical values of outdoor temperature in relation to the voltage:
Table 10-1
(Reference)
;
When the thermistor is open, in open status, or is disconnected, microcomputer pins € - @ are approx. 0 V; when
the thermistor is shorted, they are approx. 5 V, and LD301 blinks seven times.
,
However, an error is detected only when the OH thermistor is shorted; in such a case, the blinking mode is entered
12 minutes after the compressor starts operation.
— 152 —
Werbung
