Hitachi Set Free mini-HNRQ1 Series, Service Manual

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MAINTENANCE
(2) Thermistor for Discharge Gas Temperature of Compressor (for Prevention of Discharge Gas Overheating)
(a) A thermistor for discharge gas 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 discharge gas temperature of compressor increases during operation, the unit is controlled
according to the following method.
●
An electronic expansion valve and high pressure refrigerant is returned to the compressor through
the accumulator, decreasing compressor temperature.
●
If the discharge gas temperature of compressor increases exceeding 132°C even if an electronic
expansion valve opens, the compressor is stopped, in order to protect the compressor.
(3) Thermistor for Outdoor Ambient Temperature
The thermistor resistance characteristics are shown in the figure below.
(4) Thermistor for Evaporating Temperature of Outdoor Unit
The characteristics for the thermistor is the same with the value of thermistor for outdoor ambient
temperature as shown in the figure below.
2.5 Electronic Expansion Valve for Outdoor Units
Items Specifications
Type UKV Series
Refrigerant Used R410A
Working Temperature Range -30°C to 70°C
Mounting Direction Drive Shaft in Vertical Direction within an Angle of 45° as Maximum
Flow Direction Reversible
Drive Method 4-Phase Pulse Motor Method
Rated Voltage DC12V+10%
Drive Condition 63PPS 1, 2 Phase Excitation
Coil Resistance (Each Phase) 46Ω+3Ω (at 20°C)
Wiring Diagram, Drive Circuit, and Activation Mode