As the mini-split market continues to grow, we are finding ourselves working with more and more flare connections, as most of the mini-splits use them. A common issue that many people find with flare fittings is that they leak. But let’s take a look at why flares may leak: bad flare, the ridge on the flare, flare is too small, or most likely they are over-tightened! Here are some suggestions to attach flare fittings properly:
First, the major mini-split manufacturers instruct you to use the flare nuts that are shipped on their equipment, not the ones shipped on the line sets. These R410 flare nuts are heavier and have more thread than standard flare nuts.
Second, after cutting the tubing, even a sharp tube cutter will leave a ridge on the inside of the pipe. Use a deburring tool to remove this ridge as it will prevent the flare from seating properly. The blade style deburring tool works best and will leave a smooth surface in the tube.
Third, use a flaring tool rated for R410A that has a clutch to prevent the over-tightening, which thins the copper too much on the flare. Ritchie, Daikin, and others offer this style of R410 flaring tool. Daikin also has a flare gauge that sets the depth of the flare and ensures a perfectly sized flare every time. Use a drop of clean refrigeration oil on the back side of the flare to allow the nut to turn without twisting the tube.
Fourth, don’t over-tighten the flare fitting, as this can cause leaks. Daikin offers preset flare torque wrenches that will allow you to properly tighten the flare fitting without over-tightening them. Always use a backup wrench when tightening any flare fitting. The Daikin preset torque wrenches come in specific sizes from ¼” to ¾” and may only fit the R410A flare nuts.
Last but not least, pressure test the system to 550 PSIG with dry nitrogen. Follow this with proper evacuation and you now have a leak free and clean system.