Analysis Of 10 Common Malfunction In Refrigeration Maintenance (III)

- Jul 31, 2019-

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6. Refrigeration system appears oil return:


1). Lack of oil can cause serious lubrication shortage. The root cause of lack of oil is not how much and how slow the compressor is, but the system is not good. The oil separator can be installed to quickly return oil and extend the compressor's return-free operation time.


2). When the compressor is higher than the evaporator, there is no oil return bend on the vertical return pipe. The oil return bend should be as compact as possible to reduce oil deposits. The spacing between the oil return bends should be appropriate. When the number of oil return bends is relatively large, some lubricants should be added.


3). The compressor starts frequently. The frequent start of the compressor is not conducive to oil return. Since the continuous operation time is short, the compressor stops, and the return air pipe does not have a stable high-speed air flow, and the lubricating oil can only remain in the pipeline. If the oil is less than the oil, the compressor will be short of oil. The shorter the running time, the longer the pipeline, the more complicated the system, the more prominent the oil return problem


7 .Refrigeration system evaporation temperatures is low:



The evaporation temperature has a great influence on the cooling efficiency. For every 1 degree reduction, the same cooling capacity is required to increase the power by 4%. Therefore, when the conditions permit, it is advantageous to increase the evaporation temperature appropriately, and the evaporation temperature is generally 5 to 10 degrees lower than the outlet temperature.


Although the evaporation temperature can be reduced by cooling, the cooling capacity of the compressor is reduced, so the cooling speed is not necessarily fast. Moreover, the lower the evaporation temperature, the lower the refrigeration coefficient, the higher the load, the longer the running time, and the higher the power consumption.


8. Refrigeration system exhausts overheating:


The main reasons for exhaust superheat are as follows: high return air temperature, motor heating, high compression ratio, reverse expansion and gas mixing, compression temperature rise, refrigerant type, and high condensing pressure.


9. Refrigeration system low intake temperature:


1). The expansion valve opening degree is too large. 


Because the temperature sensing element is loosely tied, the contact area with the return air pipe is small, or the temperature sensing element is not wrapped with the heat insulating material and the wrapping position is wrong, the temperature measured by the temperature sensing element is inaccurate, close to the ambient temperature, and the expansion valve is operated. The degree of opening increases, resulting in too much liquid supply.


2). The charge refrigerant such as refrigerant r134a ,r404a,r407c,r134a is too much. 


The refrigerant charge of gas such as HFC R134A, R22, FREON R404A,HFC 410A is too much, occupying a part of the volume inside the condenser, so that the condensing pressure is increased, and the liquid entering the evaporator is increased. The liquid in the evaporator cannot be completely vaporized, so that the gas sucked by the compressor contains liquid droplets. Thus, the temperature of the return air duct drops, but the evaporating temperature does not change because the pressure does not decrease, and the degree of superheat decreases. Even if the small expansion valve is closed, there is no significant improvement.


10. Refrigeration system lack of fluoride:


1)When the amount of fluorine is small or the regulating pressure is low (or partially blocked), the valve cover (corrugated pipe) of the expansion valve and even the inlet port will be frosted; when the amount of fluorine is too small or substantially no fluorine, the appearance of the expansion valve No reaction, only a little sound of the airflow can be heard.

2) to see which end of the ice from the beginning, is from the liquid separation head or from the press back to the gas tube, if the liquid separation head is the lack of fluorine, from the press is more fluorine.