C. Hard to return oil
1. When the compressor is higher than the evaporator, the oil return bend on the vertical return pipe is necessary. The oil return bend should be as compact as possible to reduce oil storage. The spacing between return oil bends should be appropriate. When the number of return oil bends is large, some lubricating oil should be added.
2. Frequent start up of compressor is not conducive to oil return. Since the compressor stops for a short continuous operation time, the lubricating oil can only stay in the pipeline before a stable high-speed air flow can be formed in the return pipe. If the return oil is less than the running oil, the compressor will be short of oil. The shorter the operation time, the longer the pipeline, the more complex the system, and the more prominent the oil return problem.
3. Lack of oil will cause serious lack of lubrication. The root cause of lack of oil is not how much and how fast the compressor runs, but the poor oil return of the system.
Installation of oil separator can quickly return oil and prolong the running time of compressor without return oil.
D. Evaporation temperature is abnormal
The evaporation temperature has a great influence on the refrigeration efficiency. The power needed to be increased by 4% in order to produce the same cooling capacity when it is reduced by 1 ℃. Therefore, it is beneficial to improve the cooling efficiency of the air conditioner by increasing the evaporation temperature properly when the conditions permit.
The evaporation temperature of the household air conditioner is generally 5-10 degrees lower than the air outlet temperature of the air conditioner. In normal operation, the evaporation temperature is 5-12 degrees and the air outlet temperature is 10-20 degrees.
Although reducing the evaporation temperature can reduce the temperature difference, the refrigeration capacity of the compressor is reduced, so the refrigeration speed is not necessarily fast. Moreover, the lower the evaporation temperature is, the lower the refrigeration coefficient is, while the load is increased, the longer the operation time is, the greater the power consumption will be.