Why We Use Dry Nitrogen
May 1, 2017 Jeff Rosenblum
We are gearing up for the air conditioning start up season and you know what that means: more AC installations. As the number of installs increase, so does the workload. Let’s not forget one critical part of any AC installation—the use of nitrogen while brazing.
Why do we use nitrogen? Nitrogen is an inert gas, meaning it is not chemically active. By using nitrogen, we prevent oxidation inside the tubing. But what causes oxidation, and why is important to us? When we are brazing copper, we use a lot of heat. This heat can cause the oxygen to react with the copper and cause oxidation. Have you ever noticed a black residue on the outside of the copper lines after brazing? Without nitrogen, this happens on the inside of the tubing also. Externally, this looks bad. Internally, this can cause harm. The black residue can break free and circulate with the refrigerant throughout the system. This can plug strainers and cause bearing damage to the compressor.
Over the years, I’ve seen a number of installs that were done without nitrogen. I have seen many plugged strainers, bad TXV’s, and ruined compressors. This is not something that we want to see on any installation, let alone a brand new one. This is a warranty call waiting to happen.
So what is the proper method? Once the piping is all fitted together, remove the Schrader cores from the service valves. Hook up the nitrogen to one of the service valves and add nitrogen. The pressure should be just enough to push the oxygen out. Allow the nitrogen to purge through for a few minutes (or longer if the line sets are long). Once this is done, release the pressure but keep a small amount of nitrogen owing through the tubing. This will keep nitrogen in the system without causing so much pressure that it will blow the braze out. Now the line can be brazed together. Once done, the nitrogen is already hooked up for a pressure test.
Using nitrogen while brazing will ensure no oxidation occurs in the system, which will reduce warranty calls. As always, if you need any technical assistance please call the Famous Supply Tech Support Team.
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