The most active and reliable way to control liquid refrigerants is to recycle. Especially when the system is filled with large amount of injection, by closing the solenoid valve of the liquid tube, the refrigerant can be pumped into the condenser and the liquid accumulator, the compressor runs under the control of the Low-voltage safety control device, thus the refrigerant is isolated from the compressor when the compressor is not running and the refrigerant is removed from the compressor crankcase. Continuous evacuation cycles are recommended during the downtime to prevent leakage of solenoid valves. If it is a time to recycle, or called a non-recycled mode of control, when the long-term shutdown will be excessive refrigerant leakage damage compressor. Although continuous recycling is the best way to prevent migration, the compressor is not protected from the adverse effects of refrigerant overflow.