The most basic maintenance skills for air conditioner failure

The most basic maintenance skills for air conditioner failure

1. The most basic maintenance skills for air conditioner failure

　　 The air conditioner is composed of a refrigeration system and an electrical system, and its operating state is closely related to the working environment and conditions, so the failure analysis of the air conditioner needs to be considered comprehensively.

　　 Failure causes can be divided into two categories, one is external or man-made failure (especially whether the power supply is normal), and the other is internal failure. When analyzing and processing failures, the reasons outside the machine should be eliminated first. After eliminating the external factors, the internal faults can be divided into two types: refrigeration system faults and electrical system faults. Generally, electrical system faults should be eliminated first. As for the electrical system failure, it can be found from the following two aspects: whether the switching power supply is transmitting power; whether the motor winding is normal. According to the above general analysis ideas, the scope of the failure can be gradually reduced, and the cause of the failure will naturally come to light.

　　 2. Preliminary inspection of air conditioner 　

　　 When the refrigeration system is running, the initial inspection is conducted by asking, touching, watching, listening, and checking. These methods are simple and effective.

1. Touch: After the compressor runs normally for 20-30 minutes, touch the temperature of the suction pipe, exhaust pipe, compressor, evaporator outlet, condenser, etc., and judge the cooling effect by hand. .

　　A. The temperature of the compressor casing is generally 90～100℃.

　　 B. Touch the surface temperature of the evaporator. The temperature of the evaporator of a working air conditioner should be the same everywhere, and its surface is cold, generally around 15 degrees, and there is condensation on the exposed copper pipe elbow.

　　C. Touch the surface temperature of the condenser. After the air conditioner is turned on, the condenser will heat up soon. The faster it heats, the faster the refrigeration. Under normal use, the temperature of the condenser can reach about 80 degrees, and the temperature of the condenser tube wall is generally 45-55 degrees. .

　　D. Touch the surface temperature of the low pressure return air pipe. Normally, the suction pipe is cold and the exhaust pipe is hot. It should feel cold to the hand. If the ambient temperature is low, there will be condensation on the surface of the low-pressure return pipe. If the return pipe does not condense, and the high-pressure exhaust pipe is hot, the compressor shell is also very hot, which is probably a refrigerant. Insufficient, if all condensation on the return pipe of the compressor and half or all of the compressor casing, it means that the refrigerant is too much.

　　E. Feel the temperature of the high-pressure exhaust pipe. It should feel hot to the touch, and hot in summer.

　　F. Touch the surface temperature of the dryer filter. Under normal circumstances, the surface of the filter dryer feels slightly higher than the ambient temperature when touched by hand. If there is a cold feeling or condensation, it means that the filter drier is slightly blocked.

　　G. Find out the air outlet temperature. The hand should feel a little cool in the wind, and the hand will feel a little cold if it stays for a long time.

　　2. Look: A. First, check whether the shape of the air conditioner is intact and whether the various parts are working properly. Secondly, check whether there are breaks in the pipes of the refrigeration system, and whether there are oil traces at each welding point. If there are oil traces at the welding point, there may be leakage. Then carefully check whether the inserts of the electrical components are loose, whether the positions of the connecting copper pipes are correct, and whether the copper pipes touch the shell. Finally, check whether the beating of the centrifugal fan blade and the axial fan blade is too large, and whether the motor and compressor have obvious vibration.

　　 B, see if the high and low pressure values are normal. When the ambient temperature is 30 degrees, the low pressure is about 0.49~0.54Mpa, the high pressure is about 1.17~1.37MPa; when the ambient temperature is 35 degrees, the low pressure is about 0.58~0.62Mpa, and the high pressure is about 1.93 Mpa; when the ambient temperature is 43 degrees , Low pressure is about 0.68Mpa, high pressure is about 2.31 Mpa.

　　C, 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 form on the capillary tube, and then it will gradually melt away, but the phenomenon of insufficient refrigerant or blockage of the pipeline will cause the phenomenon of frost. It is worth noting that when the outdoor heat exchanger works in a heat pump cycle in winter, it is a low-pressure, low-temperature component, and refrigerant leakage and blockage may also occur. If there is frost on the pipe section from the outlet of the capillary tube to the inlet of the outdoor heat exchanger and the other parts are dry, it indicates that the capillary tube is half blocked. On the surface, the phenomenon of insufficient refrigerant and semi-clogging are the same.

It should also be pointed out that when the air conditioner is running, you should generally take a look at the external working conditions of the air conditioner, such as 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., in order to eliminate Factors such as external reasons and improper installation and use.

　　3. Listen: carefully listen to whether the sound of the whole machine is normal. When the air conditioner is running, it will make a certain sound, but if you hear some abnormal sound, it will be a problem. For example, when the compressor is running, there is a "humming" sound, which can immediately be determined that the compressor motor cannot start normally. At this time, you should turn off the power immediately to find the cause; the "hiss" sound is the high-pressure airflow sound generated after the high-pressure damping tube in the compressor is broken; the "click" sound is the collision sound of the metal inside the compressor; "Dangdang" sound is the impact sound of the suspension spring in the compressor falling off or breaking. For an open-type compressor, a slight and uniform "click" or a slight "di" tapping sound of the valve plate will generally be emitted; if there is a "through" sound, it is the sound of compressor liquid tapping, that is, there is a large amount of refrigerant The keyway of the suction compressor flywheel is matched with the loose impact sound; the "pap" sound is the clapping sound after the belt is damaged. The sound of centrifugal fan and axial flow fan should be balanced and uniform. If there is rubbing or the shaft is not right, abnormal sound will appear. When shutting down, when you hear a lighter and lighter airflow sound like "sizzling" (emitted when the system pressure is balanced), you know that the system is basically not blocked. In addition, other noises can be judged by auditory sense, such as: the sound of the extension axial fan hitting the iron sheet of the casing; the "squeaking" sound of the fan lacking oil; the "chattering" of the centrifugal fan and the foam casing of the fan Sound; the sound of loosening and vibration of the bottom corner bolts of the compressor; the sound of the capillary tube touching the shell.

4. Check: generally use pressure gauges, semiconductor point thermometers, clamp ammeters, multimeters, etc. to measure system pressure, temperature, power supply voltage, insulation resistance, and operating current to check whether the system meets the requirements. Use halogen leak detectors or electronic leak detectors to check the refrigeration Whether the agent leaks. For window air conditioners, it is very convenient to check the current, voltage and resistance with a clamp-on ammeter. The current reading should be around the rated current range (the current varies slightly with temperature). For split-type air conditioners, using a manifold meter to detect high and low pressures is also a practical, fast and effective method of judging. When the ambient temperature is around 30°C (under air conditioning and refrigeration conditions), if the pressure (gauge pressure) of the low pressure gauge is below 0.4MPa, it indicates that the refrigerant is insufficient or leaking. The normal value of the pressure (gauge pressure) of the high-pressure gauge should be about 2MPa, too high or too low indicates abnormality. If a blockage occurs at the outlet of the condenser, the high pressure pressure will increase, while the low pressure pressure will decrease.

The conventional items for inspection and observation are as follows: (1) low pressure pressure; (2) high pressure pressure; (3) equilibrium pressure at shutdown; (4) suction pipe temperature; (5) exhaust pipe temperature; (6) compressor temperature ; (7) Condenser; (8) Evaporator; (9) Filter; (10) Capillary tube; (11) Working current.

　　 5. Analysis: After one look, two touches, three listenings, and four tests, 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 conduct a comprehensive analysis, judge the actual part of the fault from the outside to the inside, and always keep a clear mind. Avoid momentary negligence, misjudgment, and unnecessary losses.

　　3. Analysis of the cause of failure of non-air conditioner itself　

　　 The reasons for the failure outside the machine include power supply and other aspects, listed as follows:

　　1. Power supply problem:

　　① The power supply voltage cannot be too low. Generally, when the voltage is 15% lower than the normal voltage of 220V, the compressor of the air conditioner is difficult to start. When the air conditioner is running, the voltage generally needs to be above 198V.

　　② The fuse in the special circuit of the air conditioner is blown due to small capacity, or the capacity is too large to protect it, poor contact of the power socket, and too small fuse capacity are not allowed.

　　③ The cross-sectional area of the power cord cannot be too small.

　　④ There are too many household appliances in the air conditioner room, and the capacity of the power cord is insufficient, which is not allowed.

　　⑤ In some areas, the network voltage is low and the internal resistance is large. Especially when high-power motors and other electrical equipment are used near the air conditioner unit, the voltage fluctuation range is often too large.

　　⑥ The power supply department temporarily cuts out or opens the switch and alarms.

　　2, installation, environment and use problems:

　　① There are obstacles before and after the air conditioner, which affects air flow and reduces heat exchange efficiency, thereby reducing the cooling capacity of the air conditioner.

　　② The temperature in the room is too high or too low, exceeding the allowable operating temperature range of the air conditioner.

　　③ The air conditioner room is not tightly closed, the doors and windows are not closed, and the indoor personnel frequently enter and exit.

　　④ Use heating appliances indoors, direct sunlight on the air conditioner, and the ambient temperature is higher than 43℃.

　　⑤ The heat dissipation efficiency of the air inlet and outlet of the condenser drops sharply, even exceeding the actual load of the compressor. Due to the change of throttling state, the evaporation area is constant and the suction temperature increases. Under this vicious cycle condition, the compressor will start and stop intermittently or jitter and stop.

　　⑥ The area of the air conditioner room is too large or the indoor height is too high, and the cooling capacity of the air conditioner is too small.

　　⑦ The air in the air conditioner room is dirty and dusty, causing the air filter to be covered with dust and dirt, and the indoor air circulation is blocked, which affects the heat exchange.

　　⑧ If the window air conditioner is installed too low or too high, it will not meet the installation requirements.

　　 4. Cleaning of refrigeration system

　　 After the insulation breakdown of the motor of the air-conditioning compressor, the short circuit between the turns, or the burning of the winding, the refrigeration system is contaminated because the burning of the motor produces a large amount of acid oxides. Therefore, in addition to replacing the compressor, capillary tube and filter drier, the entire refrigeration system must be thoroughly cleaned.　

　　 The degree of pollution of the refrigeration system can be divided into: mild and severe. The refrigerating oil in the refrigeration system is not completely polluted when it is lightly polluted. When the refrigerant and refrigerating oil are discharged from the process tube of the compressor, the color of the oil is transparent. If it is tested with litmus paper, the oil is light yellow (normally white). Severe pollution is serious. When you open the process tube of the compressor, you can smell the tar immediately. Pour out the frozen oil from the process tube. The color turns black. Soak the litmus paper in the oil. After 5 minutes, the color of the paper changes. Is red. The cleaning agent for air conditioning system cleaning is R113. Before cleaning, discharge the refrigerant in the refrigeration system pipeline, disassemble the compressor, and discharge a small amount of refrigerating oil from the process pipe to check its color and smell, and to see if there are impurities or foreign substances to determine the degree of pollution in the refrigeration system.　

　　The cleaning process is as follows: first pour the cleaning agent R113 into the tank, then start the pump, make it run, and start cleaning. For mild pollution, as long as the circulation is about 1 hour. For severe pollution, it takes 3-4 hours. After washing, the cleaning agent can be recovered, but it can be reused after treatment. The cleaning agent in the reservoir must be recovered from the liquid pipe. If the cleaning agent is dirty for a long time, the filter will be clogged and dirty. The cleaning agent and filter should be replaced before proceeding. After cleaning, the refrigeration pipeline should be purged with nitrogen and dried. The tank, filter and pump must be partially disconnected from the pipeline during the drying process. And install blind plates on the flanges of the hydraulic pipes and suction pipes, and then use a vacuum pump to vacuum the system. During the vacuuming process, blow hot air to the outside of the refrigeration pipeline at the same time to facilitate rapid drying. Finally, install the refrigeration pipeline as it is, and replace it with a new compressor and filter.

　　 Note: ① In order to avoid the leakage of cleaning agent, pressure hose should be used, and the joint part must be tightly wrapped with tape. ② For models that use expansion valves, remove the expansion valve and replace it with a bypass pipe. ③If moisture enters the refrigeration system, it must be drained. ④ When the compressor is burnt to produce acidic substances, it must be blown with nitrogen.

　　 Five, exhaust air

The air containing moisture remaining in the refrigeration cycle will cause the condensing pressure to increase, the operating current to increase, the refrigeration efficiency to drop, or the blockage (ice block) and corrosion, causing the compressor cylinder to fuzz, copper plating and other faults, so the pipe must be eliminated air.

Methods as below:

　　⑴ Use the refrigerant of the air conditioner itself to exhaust air. Unscrew the back cover nut and fluorine filling nozzle nut of the high and low pressure valve, open the high and low pressure valve core (turn 1/4 1/2 turn), wait for about 10 seconds, and then close it. At the same time, use an Allen wrench to push the fluorine filling needle upward from the fluorine filling nozzle nut of the low pressure valve, and air will be discharged. Stop emptying when cold air comes out of the hand. The fluorine emission should be less than 20g.

　　⑵ Use a vacuum pump to exhaust air. First unscrew the valve fluorine filling nozzle nut, and connect it with a vacuum connection hose. Turn the "LO" knob counterclockwise to turn it on, and then turn on the vacuum pump to vacuum. After stopping the vacuum, unscrew the nut of the valve back cover, and use an Allen wrench to unscrew the valve core in a counterclockwise direction to the end. At this time, the passage of the refrigeration system is opened. Then remove the connecting hose from the valve, and tighten the connecting nut of the valve with the back cover nut.

　　 (3) Use an independent refrigerant tank to add freon to exhaust air, connect the refrigerant tank filling hose to the low pressure valve fluorine filling nozzle, and slightly loosen the connecting nut on the high pressure valve of the outdoor unit. Loosen the valve of the refrigerant tank, charge it with refrigerant for 23 seconds, and then close it. After the refrigerant flows out from the high-pressure valve connecting nut for 10-15 seconds, tighten the connecting nut. Remove the filling hose from the fluorine filling nozzle, and use an Allen wrench to push the fluorine filling valve core thimble to release the refrigerant. When the noise is no longer heard, loosen the thimble, tighten the fluorine filling nozzle nut, and open the high-pressure valve core of the outdoor unit.

　　 Six, charge refrigerant.

　　 For hermetic compressors, filling Freon often uses the low-pressure income method.

1. Pour the refrigerant from the large steel cylinder into the small steel cylinder before filling. The method is: first put the small steel cylinder for repair into a container with ice cubes to cool down, and then use a rubber hose to The small cylinder is connected, but the valve of the large cylinder is temporarily not open. Loosen the joints of the large steel cylinder valve and the small steel cylinder, use Freon gas to exhaust the air in the hose, then close the valve of the large steel cylinder and tighten the hose connection of the small steel cylinder. Open the valves of the large and small steel cylinders and charge the refrigerant. When the charge reaches 80%, close the valves of the large and small steel cylinders and remove the hoses.

　　2. When charging refrigerant from a steel cylinder into the refrigeration system, the steel cylinder can be connected to the repair valve, or the middle joint of a compound pressure gauge can be used for charging. Open the small steel cylinder and turn it upside down. After the air in the pipe is discharged, tighten the joint and fill it with refrigerant. When the gauge pressure does not exceed 0.15Mpa, close the through valve. Start the compressor to suck in the refrigerant and observe the frosting of the evaporator. When the evaporator is full of frost or condensation, the charging can be stopped.

　　 Accurate judgment method of refrigerant charge:

　　1, measure the weight. When filling Freon, prepare a small scale in advance, put the refrigerant cylinder into a container, and then fill the container with warm water below 40°C (applicable to low-pressure charging refrigerant vapor for air conditioners). Write down the weight of the steel cylinder, warm water and container before filling, and observe the pointer during the filling process. When the reduction of refrigerant in the cylinder is equal to what is needed