How to judge the operating status of refrigeration equipment and fault analysis through senses

Refrigeration equipment is composed of refrigeration system and electrical system, and its operating state is closely related to the working environment and conditions, so the failure analysis of refrigeration equipment needs to be considered comprehensively. The causes of failures can be divided into two categories: one is off-board or man-made faults (especially whether the power supply is normal), and the other is in-machine faults.
When analyzing and dealing with faults, the first thing to do is to rule out the cause outside the machine. After eliminating the factors outside the machine, the faults in the machine can be divided into two categories: refrigeration system faults and electrical system faults, and the electrical system faults should generally be eliminated first. As for the fault of the electrical system, it can be found from the following two aspects: whether the switching power supply is transmitted, and whether the motor winding is normal. According to the above general analysis idea, the scope of the fault can be gradually narrowed, and the cause of the fault will naturally be revealed. When the refrigeration system is running, the method of asking, touching, seeing, listening and checking is used for the preliminary inspection. These methods are simple and effective.
touch
After 20~30 minutes of normal operation of the compressor, touch the temperature of the suction pipe, exhaust pipe, compressor, evaporator outlet, condenser and other parts, and judge the refrigeration effect by feel.
Feel the surface temperature of the evaporator: The temperature of the evaporator of the working air conditioner should be the same everywhere, and its surface is cool, generally around 15 degrees, and there is condensation at the exposed copper pipe elbow.
Feel the surface temperature of the condenser: after the air conditioner is turned on and running, the condenser will soon heat up, the faster it heats up, the faster the refrigeration, under normal use, the temperature of the condenser can reach about 80 degrees, and the temperature of the condenser pipe wall is generally 45-55 °C.
Feel the surface temperature of the low-pressure return pipe: Normally, the suction pipe is cold and the exhaust pipe is hot. If the return pipe does not condense, and the high-pressure exhaust pipe is relatively hot, the compressor shell is also very hot, it is likely that the refrigerant is insufficient, if all the condensation on the return pipe of the compressor is condensed and reaches half or all of the compressor shell, it means that the refrigerant is too much.
Feel the temperature of the high-pressure exhaust pipe: It should feel hot to the touch, and it is still hot in summer.
Touch the surface temperature of the filter drier: Under normal circumstances, the surface of the filter drier feels slightly higher than the ambient temperature. If there is a cold feeling or condensation, it means that the filter drier has a slight blockage. Feel the temperature of the air outlet: the hand should feel a little cool when the air comes out, and the hand will feel a little cold after staying for a long time.
listen
Listen carefully to whether the sound of the whole machine is normal: when the refrigeration equipment is running, it will make a certain sound, but if you hear some abnormal sounds, there is a problem, such as listening to the compressor running, there is a "hum" sound, which can immediately be determined to be the sound of the compressor motor can not start normally, at this time, the power should be turned off immediately to find the reason.
The "hiss" sound is the high-pressure airflow sound that occurs after the high-pressure damping tube in the compressor is broken, the "click" sound is the collision sound of the metal inside the compressor, and the "dangdang" sound is the impact sound after the hanging spring in the compressor falls off or breaks.
see
Look at whether the work of each component is normal: secondly, see whether the pipelines of the refrigeration system are broken, whether there are oil stains at each weld, and whether there are oil stains at the solder joints, there may be leakage. Then take a closer look at whether the inserts of the electrical components are loose, whether the position of the connected copper pipes is correct, and whether the copper pipes touch the shell. Finally, look at whether the beating of the centrifugal fan blade and the axial flow fan blade is too large, whether the motor and compressor have obvious vibration, and see whether the high and low pressure values are normal.
Look at the frosting of the low-pressure part of the capillary: during normal refrigeration, at the beginning of the compressor operation, a thin layer of frost will be formed on the capillary, and then it will gradually melt away, but the phenomenon of frost hanging will occur if the refrigerant is insufficient or the pipeline is blocked. It is worth noting that when the outdoor heat exchanger works in the heat pump cycle mode in winter, it is a low-pressure, low-temperature component, and refrigerant leakage and clogging can also occur. If there is frost on the section from the capillary outlet to the outdoor heat exchanger inlet and the other parts are dry, the capillary is half-blocked. On the surface, the phenomenon of insufficient refrigerant and semi-clogging is consistent.
Note: Whether the indoor and outdoor ambient temperature is too high or too low, whether the filter is too dirty or whether there is poor ventilation, etc., so as to rule out external reasons and improper installation and use.
examine
Generally, pressure gauges, clamp ammeters, multimeters, etc. can be used to measure whether the system pressure, temperature, power supply voltage, insulation resistance, and operating current meet the requirements, and check whether the refrigerant leaks with bubble water or leak detector.
When the ambient temperature is about 30°C (under the condition of air conditioning and refrigeration), if the pressure (gauge pressure) of the low pressure gauge is less than 0.4MPa, it indicates that the refrigerant is insufficient or leaking. The normal value of the pressure gauge (gauge pressure) should be about 2MPa, too high or too low indicates that there is an abnormality. A blockage at the outlet of the condenser can increase the pressure at high pressure and decrease at low pressure.
The usual items to be inspected and observed are as follows: low pressure, high pressure, equilibrium pressure when shutting down, suction pipe temperature, exhaust pipe temperature, compressor temperature, condenser, evaporator, filter, capillary, operating current.
analyse
Further analyze the location of the fault and the severity of the fault. Since the refrigeration system, electrical system and air circulation system are all related to each other and affect each other, it is necessary to analyze them comprehensively and judge the actual location of the fault from the surface and the inside, and always keep a clear head. To avoid a moment of negligence, judgment error, cause unnecessary losses.
To judge the failure of the refrigeration system, it is necessary to judge the system pressure, temperature and operating current when the air conditioner is running, not only to apply the theoretical knowledge of refrigeration, but also to carefully observe the situation of each part of the refrigeration system, and then make the correct judgment results.
Fault analysis and treatment of refrigeration equipment is a systematic process, and it is first necessary to eliminate external factors such as power supply and other human faults. After determining that the external conditions are normal, the internal faults are mainly investigated, which are usually divided into two parts: refrigeration system failures and electrical system failures.
For electrical system faults, firstly, check whether the switching power supply is supplied normally, and secondly, check the working status of the motor winding. Through step-by-step troubleshooting, fault points can be accurately located.
According to the operation status of the refrigeration system, the preliminary judgment can be made by the method of "touching, listening, watching and checking":
Touch: By touching the temperature changes of various key parts (such as compressors, evaporator outlets, condensers, low-pressure return pipes, etc.), we can understand the refrigeration effect and whether there are problems such as too much or insufficient refrigerant.
Listen: Listen to whether the sound of the whole machine is normal, abnormal sound may indicate that there is a fault in the compressor, damping tube, hanging spring and other components.
Look: Observe whether the components are working normally, check whether the refrigeration system pipelines are broken, whether there are oil stains at the welds (may be signs of leakage), and whether the inserts of electrical components are loose, whether the fan blades beat too much, and whether the motor and compressor vibrate obviously.
Check: Use pressure gauges, ammeters, multimeters and other tools to measure whether the system pressure, temperature, power supply voltage and other parameters meet the standards, and at the same time use the leak detector to check the refrigerant leakage, and pay attention to the influence of environmental temperature, filter cleanliness and other factors on the operation of the equipment.
Finally, according to all the information collected, a comprehensive analysis is carried out to accurately judge the location and severity of the fault from the appearance, so as to avoid the loss caused by misjudgment and repair the fault in a timely and effective manner.