Refrigerant leakage is too dangerous. Solve it quickly and take precautions!

Recently, safety accidents such as explosions and fires caused by refrigerant leakage have occurred frequently. With the withdrawal of R22 refrigerant, new refrigerants such as R407C, R410A, R134a, R290, and R32 have gradually entered the market. The flammability of new refrigerants R290 and R32 has increased the danger coefficient of air conditioner installation and maintenance. Once a leakage occurs, it may lead to unimaginable consequences.

So how can we prevent refrigerant leakage?

The following are the 9 parts of the air conditioner that are most prone to leakage and the solutions. It is hoped that every technician can check carefully to prevent problems before they occur.
1. Evaporator Leakage
There are many welds on the left and right sides of the evaporator, and there are also many possible leakage points. The leakage of newly installed air conditioners is mainly due to the poor welding skills of the employees of the air conditioner manufacturer. Without heating the copper tube red (the temperature does not reach 600°C～700°C), the welding rod is placed at the weld, and the copper tube and the solder cannot be fused together, resulting in poor welding at the weld, slag, and an uneven surface.
For newly installed air conditioners, after opening the shut-off valve of the outdoor unit and exhausting the air in the indoor unit, the sound of the indoor unit evaporator leakage can sometimes be heard with the ears. It can be seen that for the leakage of the air conditioner, the solder joints of the evaporator cannot be ignored.
Solution:
When the evaporator leakage is found, it is best to remove it for welding to prevent the plastic shell of the evaporator from being deformed by the heat flame, which will be difficult to explain to the user.

The removal method is as follows:
(1) Locate the leakage point accurately and make a mark.
(2) If there is still refrigerant in the refrigeration system, the refrigerant should be stored in the outdoor unit first.
(3) Use two 8-inch or 10-inch wrenches to remove the connection lock nuts of the indoor unit, and remove the electrical box on the right side of the indoor unit.
(4) Remove the fixed pipeline and splint on the back side of the evaporator, and remove the left and right positioning screws of the indoor evaporator.
(5) Gently lift the pipeline 20 from the back side of the indoor unit with the left hand to move the evaporator forward. Pull the evaporator out 5cm with the right hand, then rotate the evaporator 90 degrees with both hands and pull it out along the pipeline. Note to operate with both hands and do not knock down the fins. After removing the evaporator, place it in a flat, clean place, and wipe the oil stain at the leakage point clean with a dry cloth. Weld the leakage point with silver solder. After a pressure test to confirm no leakage, install the evaporator back onto the plastic frame of the indoor unit in the reverse order of disassembly.
2. Leakage at the Connection of the Indoor Unit
If the air conditioner is operating normally but there is no cold air blowing out from the indoor unit, it indicates that there is a fault in the refrigeration system. If oil stains are found at the connection of the indoor unit, it means that the refrigerant is leaking here. First, tighten the "nuts" at the connection with two wrenches, then rub dishwashing liquid to create foam and apply it to check if there are bubbles blowing out at the connection. If not, refrigerant can be added from the bypass of the low-pressure gas valve, with the low pressure being 0.5MPa as the standard.

After stopping the machine, check the nut again with dishwashing liquid. If there are still no bubbles generated after 3 to 5 minutes, it means that the leakage fault at the connection has been eliminated.
If there are bubbles generated when using dishwashing liquid for leak detection, it means that there are cracks or damage in the flared end of the pipeline, and the flared end must be remade. Before making it, first connect the power supply, set the cooling mode with the remote control, and let the compressor run for 5 minutes. Then close the low-pressure liquid valve first, and close the low-pressure gas valve 40 to 50 seconds later. At this time, touch the off key on the remote control with your hand to make the air conditioner stop running. Use two 10-inch wrenches to unscrew the lock nut at the connection of the indoor unit, check the damage degree of the flared end and analyze the cause of the leakage, so as to accumulate more maintenance experience for yourself.
Solution:
The leakage at the connection is generally due to cracks or damage in the flared end, and the flared end must be remade. Before making it, first connect the power supply, set the cooling mode with the remote control, and let the compressor run for 5 minutes. Then close the low-pressure liquid valve first, and close the low-pressure gas valve 40 to 50 seconds later. At this time, touch the off key on the remote control with your hand to make the air conditioner stop running. Use two 10-inch wrenches to unscrew the lock nut at the connection of the indoor unit, check the damage degree of the flared end and analyze the cause of the leakage, so as to accumulate more maintenance experience for yourself.
3.

Leakage of the Outdoor Unit Shut-off Valve
The leakage of the shut-off valve core of the outdoor unit mostly occurs after the unit is relocated. Due to the back-and-forth rotation of the switch valve shaft in and out, and the aging of the rubber ring over the years, the rubber ring for external shaft sealing is worn out, resulting in the leakage of the shut-off valve. When using dishwashing liquid for leak detection, a small bubble can be found to emerge in about 3 minutes. By adding an asbestos ring gasket inside the secondary sealing cap, the minor leakage fault can be eliminated. If the leakage is severe and a "hissing" sound can be heard, the refrigerant can be released from the low-pressure gas lock nut of the outdoor unit. When releasing the refrigerant, there should be a refrigerant pressure of 0.1MPa left in the pipe to prevent air from entering the system, which will bring trouble to the vacuuming process.
Solution:
Remove the limit snap ring of the shut-off valve with a pair of needle-nose pliers. Use an inner hexagon wrench to screw out the shut-off valve screw. Block the leakage point with the left hand, and quickly wind 4 turns of PTFE tape around the screw thread and the sealing ring of the screw with the right hand, and then quickly screw in the shut-off valve screw and install the snap ring. Then wind 2 to 3 turns of PTFE tape around the secondary sealing thread and install the secondary sealing cap.
Add F22 refrigerant from the gas filling port of the low-pressure gas shut-off bypass valve. When the gauge pressure reaches 0.3MPa, turn on the machine with the remote control and continue to add R22 gas until it is appropriate to reach 0.45MPa. When adding gas, it should be added slowly, and do not be too hasty, so as not to add too much R22 gas, which will increase the maintenance cost. After adding enough R22 gas as required, let the air conditioner stop running for 3 to 5 minutes. After the refrigeration gas in the system is balanced and the pressure rises, use dishwashing liquid to detect leakage at the secondary sealing outer cap. Confirming no leakage means that the PTFE tape wound around the shut-off valve screw is well sealed, and the leakage fault is eliminated.
4. Leakage of the U-shaped Pipe of the Outdoor Compressor
The leakage of the U-shaped exhaust pipe of the outdoor compressor is relatively common. The main reason is that the copper pipe wall is thin and the material quality is poor. After being bent into a U-shaped bend, small cracks appear, and the vibration generated when the compressor is working makes the cracks larger. Most of these leakage faults will leak out all the gas, and it is only found after inspection when there is no cold air blowing out from the indoor unit.
Solution:
The maintenance method is: wipe the oil stain at the leakage point clean with a soft cloth, and weld the cracked and leaking part of the copper pipe with silver solder. Before welding, it is best to find a section of copper pipe thicker than the outer diameter of the exhaust pipe, saw it open with a hacksaw, and wrap it around the cracked part to prevent leakage from this place again due to vibration.
When repairing, never remove the U-shaped pipe. Otherwise, the high-temperature and high-pressure refrigerant gas discharged by the compressor will directly enter the condenser, reducing the heat dissipation of the condenser and decreasing the refrigeration capacity. At the same time, the compressor will vibrate more severely during operation. After the U-shaped pipe is welded, add R22 gas from the bypass nozzle of the low-pressure gas shut-off valve. Test the pressure and check for leaks. If there are no bubbles blowing out from the weld, it means that the leakage fault of the U-shaped pipe has been eliminated.
5. Leakage Caused by Vibration and Wear of the Capillary Tube of the Outdoor Unit
The reason why the air conditioner does not cool and the refrigerant leaks may also be the vibration generated when the compressor is working, which causes the two pipes to resonate and rub against each other, wearing out the pipe wall and leaking out all the refrigerant.
Solution:
The elimination method is: saw open the red copper pipe and wrap it around the leaking part of the capillary tube, and then weld it with silver solder. You can also replace the capillary tube with the same inner diameter and specification. Before replacement and welding, there should be no flammable and explosive materials within 1.5m around. There should be an iron plate to block behind the capillary tube.
When welding, the flame should not be too large. It is better to use a neutral flame at medium heat. When the temperature reaches about 600°C, quickly put the silver welding rod into the weld. When the solder and the copper pipe are melted together, quickly move the welding torch away, otherwise the capillary tube will be burned through. Maintenance personnel need to slowly experience this technique during welding and gradually master the welding technology.
6. Leakage of the Low-pressure Bypass Valve Core
To replenish the refrigerant (commonly known as "adding fluorine") in the refrigeration system of a split air conditioner, it must be filled from the low-pressure bypass. Use a gas filling pipe with a thimble to push open the low-pressure gas filling valve rod, and connect the refrigerant gas in the refrigerant cylinder with the refrigerant gas in the air conditioner to carry out the filling.
Solution:
The reason for the leakage of the valve core is that the thimble of the gas filling pipe is adjusted too long. After pushing the thimble of the bypass gas valve in, it cannot bounce back, and the valve core cannot return to its original position. The elimination method is to insert the special key of the air conditioner into the gas filling valve core to apply a force to the valve core, so that the valve core spring pops out, and the leakage fault of the valve core can be eliminated.
7. Leakage of the Compressor Terminal Post
According to experience, the leakage of the compressor terminal post accounts for more than 2% of the leakage faults. Remove the outer cover of the overcurrent and overheat protector. If there are oil stains around the compressor terminal post, it indicates that there is a leakage point.
Solution:
The elimination method is: first pull out the power plug of the air conditioner and write a note "Someone is repairing the air conditioner on the roof. Do not insert the power plug" and hang it on the socket. This is to prevent the maintenance personnel from repairing the outdoor compressor on the top floor and the indoor personnel from accidentally inserting the power plug, causing a personal electric shock accident. Then use a F22 gauge at the low-pressure gas filling bypass valve to test the pressure of the system.
If the pressure in the system is zero at this time, 0.3MPa pressure of refrigerant gas can be first charged into the system to prevent the situation where there is no pressure in the system. When using dishwashing liquid to detect leaks, the dishwashing liquid may enter the compressor oil through the leakage point, causing the compressor to seize. If the pressure gauge shows that the system has pressure, you can rub dishwashing liquid to create foam, check the leakage part of the terminal post, and make a mark with a flathead screwdriver. Wipe the oil stains around the terminal post clean with a dry cloth dipped in alcohol, and use sandpaper to polish the area around the terminal post to create new edges. Then use a hacksaw blade to scratch marks on the new edges to facilitate the adhesion of the adhesive. At this time, release the gas in the system, connect a vacuum pump, and evacuate the system. When the system pressure reaches -0.1MPa, prepare C31 two-component adhesive according to the ratio of 1:1 and apply it to the connection.
Since the refrigeration system is in a vacuum state, the C31 adhesive can penetrate into the leakage point. After applying the adhesive to the leakage point, use a 100W light bulb to bake the glued area for 30 minutes to make the adhesive easier to penetrate into the leakage point. Note that the distance between the light bulb and the C31 adhesive should not be too close, and it is appropriate to be 20cm away from the C31 adhesive. Otherwise, the adhesive will be melted and flow around the compressor, reducing the effect of plugging the leak. Two hours after gluing the compressor terminal post, you can test the pressure, check for leaks, evacuate the system, add fluorine, and test the machine to restore refrigeration.
8. Leakage at the Concave and Deformed Part of the Pipeline
The leakage at the concave and deformed part of the pipeline mostly occurs after home decoration. Some decoration workers do not know that there is refrigerant in the refrigeration pipeline and bend it casually. Since there is an insulation sleeve outside the pipeline, it is not easy to find after it is bent and deformed. After the pipeline is concave and deformed, the refrigerant leaks out. When the machine is turned on again to add fluorine, the refrigeration system shows the symptoms of two throttlings.
Solution:
Example: A KRR-32GW split air conditioner does not cool. Test the pressure with a pressure gauge, and the pressure gauge shows a negative pressure. After adding gas to 0.45MPa, the noise of the compressor increases, and there is no cold air blowing out from the indoor unit. Remove the outer shell of the indoor unit, touch the evaporator with your hand, and find it is not cold. Peel off the insulation sleeve of the pipeline of the indoor unit, and find that the low-pressure liquid pipe is concave and deformed. Cut off the concave and deformed throttling part with a cutter, adopt the method of butt joint with an outer sleeve pipe, weld it with silver solder, and then test the pressure again, check for leaks, evacuate the system, add fluorine, and turn on the machine with the remote control. However, the air conditioner continues to show the above symptoms, indicating that there are still two throttling parts in the pipeline. Continue to peel off the insulation sleeve of the outdoor pipeline, and find that the low-pressure gas pipe of the outdoor pipeline is also concave and deformed. After repairing and welding the outdoor pipeline, turn on the machine with the remote control, and the air conditioner restores refrigeration.
9. Leakage of the Four-way Reversing Valve
There are more leaks at the included angle of the three copper pipes below the four-way valve of the heating and cooling type air conditioner. If there are oil stains at the included angle, it indicates that there is a leakage point. The repair method is: first wipe the oil stains clean with a towel, detect the leak with dishwashing liquid, mark the leakage point with a steel needle, then release the refrigerant, and wrap and cool the four-way reversing valve with a wet towel. When welding, according to your own mastery of the flame technique, aim at the leakage point. When the included angle reaches the welding temperature, quickly touch the silver welding rod to weld. The operation method should be fast, and strive for a successful welding at one time, and there should be no leakage after the pressure test.
Solution:
The repair method is: first wipe the oil stains at the included angle clean with a towel, detect the leak with dishwashing liquid, mark the leakage point with a steel needle, then release the refrigerant, and wrap and cool the four-way reversing valve with a wet towel. When welding, according to your own mastery of the flame technique, aim at the leakage point. When the included angle reaches the welding temperature, quickly touch the silver welding rod to weld. The operation method should be fast, and strive for a successful welding at one time, and there should be no leakage after the pressure test.
For beginners who encounter the leakage fault at the included angle of the four-way reversing valve, it is best to use the adhesive method to plug the leak. Because the nylon valve core slider is close to the included angle of the leakage point, and overhead welding has a certain difficulty. Improper operation will bake and deform the valve core. Once the slider of the four-way valve leaks air, the air conditioner can neither cool nor heat, changing from the original minor leakage fault to a major fault that requires the replacement of the four-way valve. This causes losses in terms of time and economy to the user. The method of using adhesive to plug the leak at the included angle of the four-way valve is the same as that of the compressor. After testing the pressure, checking for leaks, evacuating the system, and adding fluorine, the leakage fault at the included angle of the reversing valve of the air conditioner can be eliminated, and the refrigeration can be restored.
I believe that every air conditioner installation and maintenance technician has a deep understanding of the danger of refrigerant leakage.

It is also hoped that the technicians can treat this issue with caution during the operation process to avoid unnecessary dangers!