Customers often encounter the situation that the constant temperature and humidity equipment is not cooling, so today we will research and discuss this issue together:

Reason one:

1. Because the temperature is not maintained, observe whether the refrigeration compressor can be started during the operation of the test chamber, and the compressor can be started during the operation of the environmental test equipment, indicating that the electrical wiring from the main power supply to each compressor is normal, and the electrical appliance There is no problem with the 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 normal and the suction pressure is in a pumped-out state, indicating that the amount of refrigerant in the main refrigeration units is insufficient.

3. Touch the exhaust and suction piping of the R23 compressor of the main unit and find that the temperature of the exhaust pipe is not high and the temperature of the suction pipe is not low (unfrosted). This also explains the host group. The lack of R23 refrigerant.

Reason two:

1. The cause of the failure was not determined. The cause of the failure was further confirmed by the control process of the test chamber. The test chamber had two sets of refrigeration units.

2. One is the main unit and the other is the auxiliary unit. When the cooling rate is relatively high, the two units work at the same time. 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 small. Since the two units work at the same time during the cooling process, there is no phenomenon that the temperature cannot be stabilized, and the indicated cooling rate is reduced. 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 stops working again. If so, the fault phenomenon shown in Figure 3 will appear.

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 is basically easy to difficult, first "outside" after "inside", first "electrical" after "cooling" context to analyze and judge, familiar with and Understanding the principle and working process of the test chamber is the basis for analyzing failures to determine faults.