Does an Air Conditioner Need Refrigerant Every Year? No, It Is Leaking
In Taiwan's hot summers, a very common line from AC repairers is: "An air conditioner always leaks refrigerant after running a while. Topping it up for NT$1,500 every summer is perfectly normal." But in refrigeration and air-conditioning theory, the refrigerant (such as R410A or R32) runs in a 100% sealed closed copper-pipe circuit, and in normal conditions it never needs a single gram added, even after 10 to 15 years of use.
If your AC blows room-temperature air, the compressor sounds dull, and when you open the side cover of the outdoor unit the high-pressure thin copper pipe (2-fen, 2 分管) is covered with a thick layer of white frost, the refrigerant pressure in the system is too low (the evaporating temperature has dropped below 0°C) and refrigerant has leaked badly. Of all AC refrigerant leaks, more than 90% occur at the mechanical flare fittings on the copper pipes that connect the indoor and outdoor units.
Warning: The demanding high pressure of R32 / R410A refrigerants: Modern inverter air conditioners use R410A or the mildly flammable R32. Their maximum operating high pressure reaches 3.8 to 4.2 MPa (about 38 to 42 kgf/cm²), roughly 1.6 times that of the old R22 refrigerant. Under such internal pressure and vibration, a single micron-scale scratch, burr or crooked spot on the flare will let high-pressure refrigerant and refrigeration oil seep out silently, day and night, until it is gone.
Five Technical Pitfalls of Poor Flaring That Cause Leaks
- Inner-wall burr not removed after cutting (missing reaming): When a pipe cutter cuts seamless copper pipe, it leaves a ring of sharp, inward-rolled burr on the inner wall of the cut. If this burr is not 100% scraped smooth with a reamer (deburring tool), the flaring cone will crush it, leaving radial micro-cracks on the copper flare face.
- Wrong pipe protrusion height in the eccentric flaring tool:
- Too much protrusion from the clamp: the flare outside diameter comes out too large, and the threads badly scratch and crush the flare edge when the nut is tightened.
- Too little protrusion from the clamp: the flare does not open wide enough, so the contact area with the metal male cone of the indoor and outdoor units is too small, and the joint can easily pull loose under high pressure.
- Dry tightening without refrigerant oil: If no small amount of clean refrigeration oil (POE or PVE oil) is applied to the inner and outer slopes of the flare, the rotating shear force of the brass nut will twist and tear the soft copper flare face as it is tightened.
- Over-tightening by feel until the flare is crushed: Many half-trained crews skip the torque wrench and tighten with two adjustable wrenches using all their strength. Excessive torque instantly thins, cracks or even shears off the base of a copper flare that is only 0.8mm thick.
- Pipe bent too sharply and flattened: Bending the copper pipe sharply within 10 cm behind the flare distorts and off-centers the pipe, which puts a constant one-sided pulling and shearing force on the flare fitting.
The Full Procedure for Standard Flaring and Torque Tightening
To make a standard flare that does not leak, a professional refrigeration technician follows a strict procedure:
- Cut the pipe square: Use a sharp roller pipe cutter and feed it in slowly while rotating. Never feed too deep in a single pass, which makes the pipe out of round and deformed.
- Ream the burr thoroughly with the cut end facing down: Point the cut end of the pipe toward the ground and use a rotating reamer to scrape the inner-diameter burr clockwise for 3 to 4 turns, leaving a clean 45-degree chamfer. With the end facing down, the tiny copper shavings fall to the ground, which keeps them from dropping into the pipe and contaminating the compressor.
- Slide on the refrigerant brass nut (remember, this comes first): Before flaring, always slide the dedicated thick brass nut onto the pipe first. Countless beginners only discover after making a perfect flare that they forgot the nut, and have to cut it off and start again.
- Clamp and flare precisely with an eccentric flaring tool:
- Use an "eccentric ratchet flaring tool (eccentric cone flaring tool)". The eccentric cone rolls the copper in contact at one point at a time, turn by turn, which leaves a mirror-smooth metal surface.
- Follow the stop gauge standard (usually the pipe protrudes about 0 to 0.5mm, flush with the top face of the clamp).
- Turn the handle steadily until the clutch clicks and slips, then reverse to back the cone out.
- Visual quality check: The flare face must form a perfectly symmetrical 45-degree flare of even thickness, with smooth inner and outer surfaces and no scratches, cracks or copper shavings.
- Apply oil and tighten to a set torque with a torque wrench:
- Apply a thin drop of the matching dedicated refrigeration oil between the male cone face and the flare (it works as both seal and lubricant).
- First turn the brass nut in by hand, smoothly all the way (at least 3 to 4 turns, to confirm there is no cross-threading or tilt).
- Tighten to the specified torque with an "AC-specific torque wrench" preset to the rated value. Stop applying force the moment the torque wrench clicks, and never apply a second pull.
| Copper pipe size |
Outside diameter |
Standard tightening torque |
Standard flare outside diameter |
| 2-fen pipe (2 分管, high-pressure thin pipe) |
1/4 inch (6.35mm) |
14 ~ 18 N·m (about 1.4 to 1.8 kgf·m) |
8.7 ~ 9.1 mm |
| 3-fen pipe (3 分管, low-pressure thick pipe) |
3/8 inch (9.52mm) |
34 ~ 42 N·m (about 3.4 to 4.2 kgf·m) |
12.8 ~ 13.2 mm |
| 4-fen pipe (4 分管, thick pipe for large air conditioners) |
1/2 inch (12.70mm) |
49 ~ 61 N·m (about 4.9 to 6.1 kgf·m) |
16.2 ~ 16.6 mm |
| 5-fen pipe (5 分管, multi-split flagship units) |
5/8 inch (15.88mm) |
68 ~ 82 N·m (about 6.8 to 8.2 kgf·m) |
19.3 ~ 19.7 mm |
Leak Detection, Re-Flaring and Metered Refrigerant Charging: Typical Prices
- Professional leak detection fee: Checking the indoor and outdoor flare joints with an electronic halogen refrigerant leak detector, or confirming the leak point with a dedicated high-foam bubble leak detector, costs a basic inspection fee of about NT$800 ~ 1,500.
- Re-flaring, vacuuming and metered refrigerant charging: Cut off the damaged flare, flare and tighten it again, pull a vacuum with a two-stage rotary vane vacuum pump to below 500 microns (microns of mercury) and let it stand to hold the vacuum, then use an electronic refrigerant scale to "inject the exact charge of R410A / R32 refrigerant" according to the weight on the outdoor unit nameplate. The going rate for the whole standard repair, labor and materials included, is about NT$2,500 ~ 4,000.
When servicing the AC system, if the indoor unit is also spraying or leaking water, see the quick air conditioner repair guide and handling common home air conditioner problems.
Flare Fitting Refrigerant Leaks: Frequently Asked Questions
Q1: Can I wrap thread seal tape (止洩帶) around a leaking flare to stop the leak?
Absolutely not. This is a serious mistake. A flare seals against ultra-high pressure through microscopic plastic deformation between copper and copper. If thread seal tape is wrapped inside the joint, fragments of tape will be flushed by the high-pressure refrigerant into the compressor, blocking the expansion valve or the tiny capillary tube and directly causing the compressor to run short of oil, seize and burn out.
Q2: Why does the AC blow no cold air after the refrigerant is gone, yet the electricity bill soars?
When an inverter AC is short of refrigerant, the indoor temperature sensor sees that the room cannot reach the set target, so the inverter control board forces the DC inverter compressor to run at "maximum overdrive speed (100% full load, even an overload frequency)" at high speed all day. With no refrigerant to absorb heat, the compressor is working for nothing, power consumption rises several times over, and the compressor windings overheat because the returning refrigerant is no longer cooling them, which makes early failure very likely.
