What do we know about flare fittings?

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 lot of us agree on one thing with flare fittings, they leak! Having worked in the commercial refrigeration industry for many years myself, I once agreed with that.

Let’s take a look at why flares may leak. Bad flare, ridge on the flare, flare is too small, or most likely we over tightened them! The following flare procedure may sound simple but it works!

First, the major mini-split manufactures 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 then 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 that prevents over tightening which will thin 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 causes a lot of leaks. Daikin offers preset flare torque wrenches that will allow you to properly tighten the flare fitting without over tightening them. Always use a back up 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 tests the system to 550 PSIG with dry nitrogen. Follow this with proper evacuation, (Daikin recommends triple evacuation) and you now have a leak free and clean system.

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