A. Return liquid
B. Start with liquid
C. Hard to return oil
D. Evaporation temperature is abnormal
E. Exhaust temperature too high
F. Liquid attack
G. Fluoride deficiency
H. Low suction temperature
I. Suction temperature too high
J. Low exhaust temperature
A. Return liquid
1. For the refrigeration system with expansion valve, the return liquid is closely related to the improper selection and use of expansion valve. Too large type selection of expansion valve, too small super heat setting, incorrect installation method of temperature sensing package, damage of thermal insulation package and failure of expansion valve may cause liquid return.
2. For a small refrigeration system with capillary, too much liquid will lead to liquid return. When the evaporator frosts seriously or the fan fails, the heat transfer becomes poor, and the non evaporated liquid will cause liquid return. Frequent fluctuation of temperature will also cause failure of expansion valve reaction and liquid return.
For the refrigeration system which is difficult to avoid liquid return, the installation of gas-liquid separator control can effectively prevent or reduce the harm of liquid return.
B. Starting with liquid
1. The phenomenon of violent foaming of lubricating oil in the compressor is called starting with liquid.
The bubbling phenomenon during the start-up with liquid can be clearly observed on the oil sight glass. The root cause is that a large amount of refrigerant dissolved in the lubricating oil and sunk under the lubricating oil suddenly boils when the pressure drops suddenly, and causes the foaming phenomenon of the lubricating oil, which is easy to cause liquid hammer.
2. Installation of crankcase heater (electric heater) on compressor can effectively prevent refrigerant migration.
Shut down for a short time and keep the crankcase heater energized. After a long-time shutdown, heat the lubricating oil for several or more hours before starting. The gas-liquid separator installed on the return pipeline can increase the resistance of refrigerant migration and reduce the migration amount.