How to Prevent and Swiftly Solve the Dangerous Refrigerant Leakage

2025-04-05

Recently, safety accidents such as explosions and fires caused by refrigerant leakage have occurred frequently. With the phasing - out 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 added a lot of danger factors to the installation and maintenance of air - conditioners. Once a leakage occurs, it may lead to unimaginable consequences.

So, how to prevent refrigerant leakage?

The following are 9 parts of an air - conditioner that are most prone to leakage and their solutions. I hope every technician can check them carefully to prevent problems before they occur.

Evaporator Leakage
There are many welds on the left and right sides of the evaporator, so there are also many potential leakage points. For newly installed air - conditioners, the main reason for leakage is that the welding skills of the employees in the air - conditioner manufacturing factory are not good. Without heating the copper pipe red (the temperature does not reach 600℃ - 700℃), the welding rod is placed at the weld. As a result, the copper pipe and the welding material cannot be fused together, causing problems such as weld inclusions, slag, and roughness.
For a newly installed air - conditioner, after opening the outdoor unit stop valve and exhausting the air in the indoor unit, the sound of the indoor unit evaporator leakage can sometimes be heard by the ear. It can be seen that for air - conditioner leakage, the welds of the evaporator cannot be ignored.
Solution:
When an evaporator leakage is found, it is best to remove it for welding to avoid deforming the plastic shell of the evaporator with the heat flame, which would be difficult to explain to the user. The disassembly method is as follows:
(1) Locate the leakage point accurately and make a mark.
(2) If there is still refrigerant in the refrigeration system, first store the refrigerant in the outdoor unit.
(3) Use two 8 - inch or 10 - inch wrenches to remove the connection lock nuts of the indoor unit, and then remove the electrical box on the right side of the indoor unit.
(4) Remove the fixed pipelines and splints on the rear side of the evaporator, and remove the left and right positioning screws of the indoor evaporator.
(5) Gently lift the pipeline 20 cm from the rear side of the indoor unit with the left hand to move the evaporator forward. Pull the evaporator out 5 cm with the right hand, then rotate the evaporator 90 degrees with both hands and pull it out along the pipeline. Note that both hands should be used for operation to avoid knocking down the fins. After removing the evaporator, place it in a flat, clean place, and wipe the oil stains at the leakage point clean with a dry cloth. Weld the leakage point with silver solder. After pressure - testing to ensure no leakage, install the evaporator back onto the plastic frame of the indoor unit in the reverse order of disassembly.
Leakage at the Indoor Unit Connection
If the air - conditioner is operating normally but no cold air is blown out from the indoor unit, it indicates a fault in the refrigeration system. If there are oil stains at the connection of the indoor unit, it means that the refrigerant is leaking here. First, use two wrenches to tighten the "nuts" at the connection, then rub dish - washing liquid to produce foam and apply it to check if there are bubbles blowing out at the connection. If not, refrigerant can be added through the bypass of the low - pressure gas valve, with the low - pressure at 0.5MPa as the standard. After shutting down the machine, use dish - washing liquid to check the nuts again. If no bubbles are generated after 3 - 5 minutes, it means that the air - leakage fault at the connection has been eliminated.
If bubbles are generated when using dish - washing liquid for leak - detection, it indicates that there are cracks or damage in the pipe flare. The flare must be remade. Before remaking, first turn on the power, set the refrigeration 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 - 50 seconds later. At this time, touch the "off" key on the remote control with your hand to stop the operation of the air - conditioner. Use two 10 - inch wrenches to unscrew the lock nuts at the connection of the indoor unit, check the damage degree of the flare, and analyze the reasons for the leakage, so as to accumulate more maintenance experience.
Solution:
Leakage at the connection is generally due to cracks or damage in the flare. The flare must be remade. Before remaking, first turn on the power, set the refrigeration 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 - 50 seconds later. At this time, touch the "off" key on the remote control with your hand to stop the operation of the air - conditioner. Use two 10 - inch wrenches to unscrew the lock nuts at the connection of the indoor unit, check the damage degree of the flare, and analyze the reasons for the leakage, so as to accumulate more maintenance experience.

3. Outdoor Unit Stop Valve Leakage

Leakage at the stop valve core of the outdoor unit mostly occurs after the air - conditioner has been relocated. Due to the back - and - forth rotation of the valve shaft during opening and closing, coupled with the aging of the rubber seal over the years, the outer - shaft sealing rubber ring is worn out, resulting in leakage at the stop valve. When using dish - washing liquid for leak - detection, a small bubble may appear in about 3 minutes. The small leakage fault can be eliminated by adding an asbestos round gasket inside the secondary sealing cap. 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, there should be a refrigerant pressure of 0.1MPa left in the pipe to prevent air from entering the system, which would cause trouble in vacuum - pumping.

Solution:
Remove the stop valve limit snap - ring with a pair of long - nose pliers. Unscrew the stop valve screw with an Allen wrench. Block the air - leakage point with the left hand, and quickly wind 4 turns of PTFE tape around the screw threads and the sealing ring of the screw with the right hand. Then, quickly screw the screw back into the stop valve and install the snap - ring. Wind 2 - 3 turns of PTFE tape around the secondary sealing threads and install the secondary sealing cap.
Add F22 refrigerant from the low - pressure gas stop bypass valve gas - filling port. When the gauge pressure reaches 0.3MPa, turn on the air - conditioner with the remote control and continue to add R22 gas until it is appropriate at 0.45MPa. When adding gas, it should be added slowly. Do not rush, otherwise, adding too much R22 gas will increase the maintenance cost. After adding the required amount of R22 gas, let the air - conditioner stop running for 3 - 5 minutes. After the refrigeration gas in the system is balanced and the pressure rises, use dish - washing liquid to detect leaks at the secondary sealing outer cap. If there is no leakage, it indicates that the PTFE tape wound around the stop valve screw has a good seal, and the air - leakage fault has been eliminated.

4. Outdoor Compressor U - shaped Pipe Leakage

Leakage of the U - shaped exhaust pipe of the outdoor compressor is quite common. The main reason is that the copper pipe has a thin wall and poor material quality. After being bent into a U - shape, small cracks appear, and the vibration generated when the compressor is working enlarges the cracks. Most of these leakage faults will cause all the gas to leak out. It is not discovered until the indoor unit stops blowing cold air.

Solution:
The maintenance method is as follows: Wipe the oil stains 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 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 further leakage due to vibration.
During maintenance, never remove the U - shaped pipe. Otherwise, the high - temperature and high - pressure refrigerant gas discharged from the compressor will directly enter the condenser, reducing the heat dissipation of the condenser and 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 stop valve. Conduct a pressure test for leak - detection. If no bubbles are blown out from the weld, it indicates that the leakage fault of the U - shaped pipe has been eliminated.

5. Outdoor Unit Capillary Tube Vibration and Abrasion Leakage

The reason why the air - conditioner does not cool and the refrigerant leaks may also be that the vibration generated when the compressor is working causes the two pipes to resonate and rub against each other, wearing through the pipe wall and leaking all the refrigerant.

Solution:
The solution is to saw open a 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 or explosive substances within a 1.5 - meter radius. There should be an iron plate to block behind the capillary tube.
When welding, the flame should not be too large. A neutral medium - sized flame is preferred. When the temperature reaches about 600℃, quickly put the silver welding rod into the weld. As soon as the welding material and the copper pipe are melted together, quickly move the welding torch away, otherwise, the capillary tube will be burned off. Such skills need to be gradually understood and mastered by maintenance personnel during welding.

6. Low - pressure Bypass Valve Core Leakage

To replenish the refrigerant (commonly known as "adding fluorine") in the refrigeration system of a split - type air - conditioner, it must be added from the low - pressure bypass. Use a gas - adding tube with a thimble to push open the low - pressure gas - adding valve stem, and the refrigerant gas in the refrigerant cylinder will be connected to the refrigerant gas in the air - conditioner, and then the refrigerant can be added.

How to Prevent and Swiftly Solve the Dangerous Refrigerant Leakage1743858233340

Solution:
The reason for the valve - core leakage is that the thimble of the gas - adding tube is adjusted too long. After pushing the bypass gas - valve thimble in, it cannot bounce back, preventing the valve core from resetting. The solution is to insert the special air - conditioner key into the gas - adding valve core to apply a force to the valve core, making the valve - core spring pop out, thus eliminating the valve - core air - leakage fault.

7. 7. Compressor Terminal Post Leakage

According to experience, compressor terminal post leakage accounts for more than 2% of leakage faults. Remove the outer cover of the over - current and over - heat protector. If there are oil stains around the compressor terminal post, it indicates a leakage point.

Solution:
The solution is as follows: First, pull out the power plug of the air - conditioner and write a note saying "Someone is repairing the air - conditioner on the roof. Do not plug in the power" and hang it on the socket. This is to prevent indoor personnel from accidentally plugging in the power while the maintenance worker is repairing the outdoor compressor on the roof, which could cause electric shock. Then, use a F22 - adding gauge at the low - pressure gas - adding bypass valve to test the pressure of the system.
If the pressure in the system is zero at this time, first charge the system with refrigerant gas at a pressure of 0.

How to Prevent and Swiftly Solve the Dangerous Refrigerant Leakage1743858233246

3MPa. This is to prevent the dish - washing liquid from entering the compressor oil through the leakage point when detecting leaks with dish - washing liquid, which could cause the compressor to seize up due to the lack of pressure in the system. If the pressure gauge shows that the system has pressure, rub dish - washing liquid to produce foam and check the leakage point around the terminal post. Mark the leakage point with a flat - head screwdriver. Wipe the oil stains around the terminal post clean with a dry cloth dipped in alcohol, and sand the area around the terminal post to create new rough surfaces. Then, use a hacksaw blade to make scratch marks on the new rough surfaces to facilitate the adhesion of the adhesive. At this point, release the gas in the system, connect a vacuum pump, and evacuate the system. When the system pressure reaches - 0.1MPa, prepare C31 two - part glue in a 1:1 ratio and apply it to the connection.
Since the refrigeration system is in a vacuum state, the C31 glue can penetrate into the leakage point. After applying the glue to the leakage point, use a 100 - watt bulb to bake the glued area for 30 minutes to make the glue penetrate the leakage point more easily. Note that the bulb should be about 20cm away from the C31 glue when baking. Otherwise, the glue may be melted and flow around the compressor, reducing the leakage - blocking effect. Two hours after gluing the compressor terminal post, pressure - test and check for leaks. Finally, evacuate the system, add refrigerant, and test the machine to restore refrigeration.

8. Leakage at Pipe Dents

Leakage at pipe dents mostly occurs after home decoration. Some decoration workers are unaware that there is refrigerant in the refrigeration pipes and bend them casually. Since the pipes are covered with insulation sleeves, the dents are not easily detectable. After the pipes are dented, the refrigerant leaks out. When the machine is turned on again to add refrigerant, the refrigeration system shows symptoms of double throttling.

Solution:
For example, a KRR - 32GW split - type air - conditioner does not cool. Test the pressure with a pressure gauge, and the gauge shows negative pressure. After adding gas to 0.45MPa, the compressor noise increases, and no cold air is blown out from the indoor unit. Remove the outer shell of the indoor unit, touch the evaporator, and it is not cold. Peel off the insulation sleeve of the indoor unit pipes and find that the low - pressure liquid pipe is dented. Cut off the dented throttling part with a cutter, use a sleeve - pipe butt - joint method, weld it with silver solder, and then re - pressure - test, check for leaks, evacuate, and add refrigerant. Turn on the machine with the remote control. However, the air - conditioner continues to show the above - mentioned symptoms, indicating that there is still another double - throttling point in the pipes. Continue to peel off the insulation sleeve of the outdoor pipes and find that the low - pressure gas pipe of the outdoor pipes is also dented.

How to Prevent and Swiftly Solve the Dangerous Refrigerant Leakage1743858233292

After repairing and welding the outdoor pipes, turn on the air - conditioner with the remote control, and the refrigeration function is restored.

9. Four - way Reversing Valve Leakage

In heating - cooling air - conditioners, there are more leakage cases at the intersections of the three copper pipes below the four - way valve. If there are oil stains at the intersections, it indicates a leakage point. The repair method is as follows: First, wipe the oil stains clean with a towel, check for leaks with dish - washing liquid, mark the leakage point with a steel needle, then release the refrigerant, and wrap the four - way reversing valve with a wet towel for cooling. When welding, according to your mastery of the flame technique, aim at the leakage point. When the intersection reaches the welding temperature, quickly apply silver welding rod for welding. The operation should be fast to strive for a successful weld on the first try. After pressure - testing, there should be no leakage.

Solution:
The repair method is: First, wipe the oil stains at the intersection marked area clean with a towel, check for leaks with dish - washing liquid, mark the leakage point with a steel needle, then release the refrigerant, and wrap the four - way reversing valve with a wet towel for cooling. When welding, according to your mastery of the flame technique, aim at the leakage point. When the intersection reaches the welding temperature, quickly apply silver welding rod for welding. The operation should be fast to strive for a successful weld on the first try. After pressure - testing, there should be no leakage.
For beginners encountering the leakage fault at the intersection of the four - way reversing valve, it is best to use the gluing method to plug the leak. Because the nylon valve - core slider is close to the intersection of the leakage point, and overhead welding is somewhat difficult. Improper operation may bake and deform the valve core. Once the four - way valve slider leaks gas, the air - conditioner can neither cool nor heat. A small leakage fault originally turns into a major fault that requires replacing the four - way valve, causing losses to the user in terms of time and economy. The gluing method for plugging the leak at the intersection of the four - way valve is the same as that for the compressor. After pressure - testing, leak - checking, evacuating, and adding refrigerant, the leakage fault at the intersection of the four - way valve of the air - conditioner can be eliminated, and the refrigeration function can be restored.