1, constant temperature and humidity test box refrigeration failure analysis. As the temperature is not maintained, observe the refrigeration compressor in the test       Whether the inspection box can be started during the operation of the inspection box and the compressor can be started during the operation of the environmental testing equipment, indicating that the electrical wiring from the main power supply to each compressor is normal, and there is no problem in the electrical system.

2. There is no problem with the electrical system and continue to check the refrigeration system. First of all, it is checked that the exhaust and suction pressures of low-temperature (R23) compressors of the two sets of refrigeration units are lower than the normal values, and the suction pressure is in an empty state, which indicates that the amount of refrigerant in the main refrigeration units is insufficient.

3 , touch the exhaust and suction pipe of the host group R23 compressor, found that the temperature of the exhaust pipe is not high, the suction pipe temperature is not low ( unfrosted ) , which also explains the host group The lack of R23 refrigerant.

4. Undetermined cause of the malfunction, the control process further confirm the binding chamber cause of the malfunction, the chamber has two refrigeration unit.

5 , one is the main unit, and the other is the auxiliary unit. When the cooling rate is relatively high, the two units work simultaneously. In the initial stage of the temperature maintenance period, the two units still work simultaneously. When the temperature is initially stabilized, the auxiliary unit stops working and the host group maintains the temperature stability. If the host group R23 is leaked, the cooling effect of the host group will be insignificant. Since the two units operate at the same time during the cooling process, there is no phenomenon that the temperature cannot be stabilized, and the indicated cooling rate decreases. In the temperature maintenance phase, once the auxiliary unit stops working, the main unit has no cooling effect, and the air in the test chamber will slowly rise. When the temperature rises to a certain extent, the control system will start the auxiliary unit to cool down the temperature and set the temperature down. In the vicinity of the fixed value (-55 °C ) , the auxiliary unit will stop working again. If so, the fault phenomenon shown will occur.

At this point, it was confirmed that the cause of the production failure was the leakage of refrigerant R23 of the low-temperature (R23) -class unit of the host group . The leakage of the refrigeration system was checked and checked by a combination of leak detector and soapy water. It was found that the valve stem of a hot gas bypass solenoid valve cracked approximately 1 cm . Replace the solenoid valve to recharge the system and the system is operating normally.

As can be seen from the above, the analysis and judgment of this fault phenomenon are basically easy to difficult, first "outside " and then "inside " , first "electrical " and "cooling " context to analyze and judge, familiar with and Learn chamber of principle and process analysis is the basis for fault judgment failures.