First, observe whether the refrigeration compressor can be started during operation. If the compressor in the high-low temperature room can be started during operation, it means that the circuit of the main power supply of the compressor is normal, and the electrical system is also normal.
1. Check the refrigeration system of the high-low temperature room
If there is no problem with the electrical system of the high-low Temperature Test Chamber, continue to check the refrigeration system. First check the two sets of refrigeration compressor units in the high-low Temperature Test Chamber. If the discharge and suction pressure of the low-temperature compressor is lower than normal, and the suction pressure is evacuated, it indicates that the amount of refrigerant in the main refrigeration unit is obviously insufficient. Then touch the exhaust pipe and suction pipe of the main engine compressor in the high-low temperature chamber. If it is found that the temperature of the exhaust pipe is not high and the temperature of the suction pipe is not low (no frost), it means that there is insufficient refrigerant in the main refrigeration unit.
The high-low Temperature Test Chamber is composed of main engine and auxiliary unit. When the cooling rate is large, the two sets of units work at the same time. At the beginning of the temperature maintenance phase, the two sets of units are still working simultaneously. When the temperature is stable, the auxiliary unit will stop working, and the main unit will keep the temperature down and stable. If the refrigerant of the main unit leaks, the cooling effect of the main unit will be reduced. As both units are operating simultaneously during cooling, the temperature will stabilize but the indicated cooling rate will decrease.
In the heat preservation stage, once the auxiliary unit stops working and the main engine has no cooling effect, the air temperature in the high-low Temperature Test Chamber will rise slowly. When the temperature rises to a certain level, the control system will activate the auxiliary unit for cooling. After reaching a certain temperature, the unit will stop working. When this process is repeated again and again, there may be failure phenomena that the auxiliary unit can no longer help, and the low temperature can no longer be achieved.
So far, it has been confirmed that the cause of the low temperature failure is the refrigerant leakage of the main refrigeration unit.
2. Troubleshooting method of high-low Temperature Test Chamber
Check for leaks in the refrigeration system of the high-low Temperature Test Chamber. Use a combination of a leak Detector and soapy water to check for leaks. If the stem of the hot gas bypass solenoid valve is cracked, replace it. If the leak is elsewhere, repair the leak with oxygen welding, then refill the system with fluorine, and the system should operate normally again.
