3-21
MAIN PARTS
3.5.2 Thermistor for Outdoor Unit
(1) Position of Thermistor
(2) Thermistor for Upper Part Temperature of Compressor
(For Prevention of Discharge Gas Overheating)
a. A thermistor for the upper part temperature of
the compressor is installed to prevent discharge
gas from overheating.
If discharge gas temperature increases
excessively lubricating oil deterioration occurs
and lubricating properties deteriorate, resulting
in short compressor life.
b. If discharge gas temperature increases
excessively, compressor temperature
increases. At the worst, compressor motor
winding will be burnt out.
c. When the upper part temperature of
compressor increases during heating operation,
the unit is controlled according to the following
method.
G An electronic expansion valve of outdoor units is (are) opened to return the liquid refrigerant to the
compressor through the accumulator, decreasing compressor temperature.
G If the compressor upper part temperature increases exceeding 132
o
C even if an electronic
expansion valve opens, the compressor is stopped, in order to protect the compressor.
In cooling operation, the above function is also available.
200
100
25 30 132 150
72.3
14.2
100
200
5.3
Resistance Value of
Thermistor (kΩ)
Temperature (
o
C)
Resistance Characteristics of Thermistor
for Discharge Gas Overheating Protection
R25 = 200kΩ
B = 3920k
0
d. If compressor upper part temperature increases excessively, the protection control is activated and
the compressor is stopped according to the following method.
Operation
Upper Part Temperature
of Compressor
Cooling Over 132
o
C 10 minutes (Continuously)
Over 140
o
C5 seconds (Continuously)
Heating Over 132
o
C 10 minutes (Continuously)
Over 140
o
C5 seconds (Continuously)
Defrosting Over 132
o
C5 seconds (Continuously)
Defecting Period
Thermostat Holder
Holder
Thermistor for
Discharge Gas
Temperature
Thermistor
for Evaporating
Temperature
Thermistor
for Outdoor Ambient
Temperature
<Example: RAS-30FSG1>
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