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1. Liquid back:
1. For refrigeration systems that use expansion valves, liquid return is closely related to the improper selection and use of expansion valves. Excessive selection of the expansion valve, too small superheat setting, incorrect installation of the temperature sensing bulb, damaged adiabatic dressing, and failure of the expansion valve may cause liquid flood back.
2. For small refrigeration systems that use capillary tubes, too much liquid will cause liquid backflow. When the evaporator is severely frosted or the fan fails, the heat transfer becomes poor, and the unevaporated liquid will cause liquid back. Frequent temperature fluctuations can also cause the expansion valve to malfunction and cause liquid backflow.
For refrigeration systems where liquid return is difficult to avoid, installing a gas-liquid separator control can effectively prevent or reduce the harm of liquid return.
2. Start with liquid:
1. The phenomenon that the lubricating oil in the compressor foams violently is called start with liquid. The blistering phenomenon when starting 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 sinking under the lubricating oil suddenly boils when the pressure drops suddenly and causes the lubricating oil to bubble, which can easily cause liquid hammer.
2. The installation of a crankcase heater (electric heater) on the compressor can effectively prevent the migration of refrigerant. Shut down for a short time to maintain the crankcase heater energized. After a long period of shutdown, heat the lubricating oil for several or ten hours before starting. Installing a gas-liquid separator on the return gas pipeline can increase the resistance of refrigerant migration and reduce the amount of migration.
Three, oil return:
1. When the compressor is higher than the evaporator, the oil return bend on the vertical return pipe is necessary. The return bend should be as compact as possible to reduce oil storage. The spacing between the oil return bends should be appropriate. When the number of oil return bends is large, some lubricant should be added.
2. Frequent compressor startup is not conducive to oil return. Since the compressor stops for a short continuous operation time, there is no time to form a stable high-speed air flow in the return pipe, and the lubricating oil can only stay in the pipe. If the oil return is less than Ben oil, the compressor will be short of oil. The shorter the operating time, the longer the pipeline and the more complex the system, the more prominent the oil return problem.
3. Lack of oil will cause serious lack of lubrication. The root cause of the lack of oil is not the amount and speed of the compressor, but the poor oil return of the system. The installation of an oil separator can quickly return oil and extend the compressor running time without oil return.
Four, evaporation temperature:
The heating temperature has a great influence on the refrigeration efficiency. When it decreases by 1 degree, it needs to increase the power by 4% to produce the same cooling capacity. Therefore, when conditions permit, appropriately increasing the evaporation temperature is beneficial to improving the cooling efficiency of the air conditioner.
The evaporating temperature of household air conditioners is generally 5-10 degrees lower than the air outlet temperature of the air conditioner. In normal operation, the evaporating temperature is 5-12 degrees, and the outlet temperature is 10-20 degrees.
Blindly lowering the evaporating temperature can cool the temperature difference, but the cooling capacity of the compressor is reduced, so the cooling speed is not necessarily fast. What's more, the lower the evaporation temperature, the lower the refrigeration coefficient, but the load increases, the operating time is extended, and the power consumption will increase.
5. Exhaust temperature is too high
The main reasons for the excessively high exhaust temperature are the following: high return air temperature, large heating capacity of the motor, high compression ratio, high condensation pressure, adiabatic index of the refrigerant, and improper refrigerant selection.
Six, liquid strike
1. In order to ensure the safe operation of the compressor and prevent the occurrence of liquid hammer, the suction temperature is required to be higher than the evaporation temperature, that is, it should have a certain degree of superheat.
2. Avoid too high or too low temperature. If the suction temperature is too high, that is, the overheating is too high, which will cause the compressor discharge temperature to rise. If the suction temperature is too low, it means that the refrigerant is not completely evaporated in the evaporator, which not only reduces the heat exchange efficiency of the evaporator, but the suction of wet steam will also cause compressor liquid hammer. The suction temperature should be 5～10℃ higher than the evaporation temperature under normal circumstances.
Seven, add fluoride
1. When the amount of fluorine is low or its regulating pressure is low (or partially blocked), the bonnet (bellows) of the expansion valve and even the liquid inlet will be frosted; when the amount of fluorine is too little or there is basically no fluorine, the appearance of the expansion valve No response, only a faint sound of airflow can be heard.
2. See from which end the icing starts, whether it is from the dispensing head or the return pipe of the compressor. If the dispensing head is lack of fluorine, the compressor is more fluorine.
8. Low suction temperature:
1. The refrigerant charge is too much, which occupies part of the volume in the condenser and increases the condensing pressure, and the liquid entering the evaporator increases accordingly. The liquid in the evaporator cannot be completely vaporized, so that the gas sucked by the compressor contains liquid droplets. In this way, the temperature of the return air duct drops, but the evaporation temperature does not change because the pressure does not drop, and the degree of superheat decreases. Even if the expansion valve is closed, there is no significant improvement.
2. The opening of the expansion valve is too large. Because the temperature sensing element is loosely bound, the contact area with the return pipe is small, or the temperature sensing element is not wrapped with insulating material and its wrapping position is wrong, etc., the temperature measured by the temperature sensing element is inaccurate and close to the ambient temperature, causing the expansion valve to operate. The opening degree increases, resulting in excessive liquid supply.
Nine, high suction temperature:
1. The refrigerant charge in the system is insufficient, or the expansion valve opening is too small, resulting in insufficient refrigerant circulation in the system, less refrigerant entering the evaporator, high superheat, and high suction temperature.
2, the expansion valve port filter is blocked, the liquid supply in the evaporator is insufficient, the amount of refrigerant liquid is reduced, and a part of the evaporator is occupied by superheated steam, so the suction temperature increases.
3. The suction temperature is too high due to other reasons, such as poor insulation of the return air pipe or the pipe being too long, which can cause the suction temperature to be too high. Under normal circumstances, the compressor cylinder head should be half cold and half hot.
Ten, exhaust temperature is too low
Exhaust pressure is too low. Although the phenomenon is manifested on the high pressure side, the reasons are mostly at the low pressure side. The reasons are:
1. The expansion valve is blocked by ice or dirty, and the filter is blocked, which will inevitably cause the suction and discharge pressure to drop; the refrigerant charge is insufficient;
2, the expansion valve hole is blocked, the liquid supply is reduced or even stopped, and the suction and exhaust pressures are reduced at this time.