Causes of compressor refrigerant backflow
Compressor refrigerant backflow can be caused by a variety of situations. Most of the causes can be attributed to:
1. Evaporator problems.
2. Overcharge and/or improper capillary tube size.
3. Faulty or improperly adjusted expansion valve.
4. Refrigerant migration.
Solutions for continuous compressor refrigerant backflow
1) Check the selection and use of expansion valve
-Re-examine whether the expansion valve is suitable. You can use the selection software of each manufacturer for quick selection and comparison or directly refer to the recommended specifications of Emerson’s “Fully Enclosed Copeland Scroll TM Refrigeration Compressor User Manual” to solve the problem in one step.
-Detect and calculate the suction superheat. After the expansion valve is opened, it should meet the compressor’s suction superheat requirements; for low-temperature applications, the recommended minimum superheat is 11k; for medium and high temperature applications, the recommended minimum superheat is 3-6k
-The expansion valve temperature sensor must be strictly insulated to avoid being affected by the ambient temperature.
2) Check the selection and use of evaporator
-Defrost regularly
-Re-examine whether the evaporator area matches the compressor’s cooling capacity
3) Refrigerant charging
Add a sight glass to the liquid pipe of the condensing unit. Observe the liquid level of the sight glass during debugging. When the system is running stably, the full liquid state meets the charging requirements. Do not overcharge.
4) Configure gas-liquid separator (suitable gas separator should meet the following conditions)
-Gas separator effective volume >= 70% of system refrigerant charge
-According to the refrigeration capacity of the compressor, the diameter of the internal oil return hole of the gas separator is recommended to be 1.5-3.5mm (the effective volume of the gas separator and the diameter of the oil return hole are recommended to be confirmed by testing), and the oil return hole filter should not exceed 30 mesh.