Wheeler On HVACR: Nitrogen Gas - The Vital Service And Installation Tool
It seems that the need for one of our industry's more important service and installation tools - dry nitrogen gas - is being overlooked more and more, especially in areas of the continent where nonunion service and installation companies dominate the market. Why have I drawn that distinction? Because union apprentice programs and their curriculum have stayed pretty stable over the years. And most have, for a fact, remained true to teaching good piping and service practices. After all, their primary focus over the years, by tradition, has been on teaching mechanics to properly install (not service) large commercial HVACR systems.
However, I have noted that in areas where building-trade unions aren't as strong, classes are being taught more frequently by industry people with little or no apprenticeship training and who may be long on service skills but who are generally weak when it comes to proper piping practices. And this is having an effect on the reliability of the equipment. What am I talking about?
Use During Initial PipingWell, consider for a moment the first and most basic need of dry nitrogen for HVACR mechanics: keeping systems clean and dry during initial piping. All systems should be brazed with a slow non-pressurized flow of dry nitrogen wisping through the copper tubing. If you don't think this is true, just braze together two pieces of copper tubing with a map-gas or oxy-acetylene rig and see what happens to the copper. You'll find all sorts of corrosion on the surface around the brazed area. And that's just the part you can see. Much of this corrosion is oxidation and it is not only found on the outside of the pipe, but also on the inside of the copper surfaces. Now the stuff on the outside just looks bad. But the stuff on the inside is eventually washed off by the flowing refrigerant and inevitably finds its way into the compressor oil, into the moving parts (piston, bearings), and into the motor windings. This is the beginning of a slow death for a compressor.
What does the flow of dry nitrogen do when brazing? Well, if there is no oxygen inside the lines, there is no oxidation, so no corrosion is formed. In addition, dry nitrogen keeps moisture-laden air out of the lines during installation, making the dehydration (evacuation) process go much faster.
We seldom find jobs, whether residential, commercial HVAC or refrigeration, that go in without any brazing. And brazing without the use of nitrogen causes eventual compressor deterioration. The more brazing there is (as in the case of rigid-tube jobs), the more critical the use of dry nitrogen becomes.
So, is there a problem with the lack of use of dry nitrogen in your area or not? Just go through your records and find out who buys dry nitrogen from you, and in what quantities - that is, assuming that your company sells it, and you should. You'll be surprised to find how little is actually being used and how bad this situation is really getting. This little survey will also indicate who the better contractors are, and who you should recommend.
This reminds me of something a strictly residential, strictly new-construction contractor once told me. His people weren't very skilled. All they did was connect up systems using pre-charged line sets, making sure all the strictly mechanical (non-brazed) connections were tight, and they opened the king valves on the units using the factory-supplied charge. They didn't know enough to braze, or evacuate, or to adjust the charge. So as the contractor pointed out, his down-and-dirty low-budget installations by non-skilled personnel were extremely reliable with few warranty call backs. Why? Because they didn't add contaminants or moisture, and they didn't overcharge the system like most “skilled” technicians would do.
Use For Leak TestingOf course, the use of dry nitrogen isn't just limited to new installations. Its greater use is for leak testing, as many service technicians have discovered over the years.
The nice thing about using nitrogen for leak testing is that the pressure is the same regardless of the temperature (unlike refrigerant alone). All the technicians have to do is put a little refrigerant into the system so their leak detectors will work, then boost the system pressure to about 250-psi with the nitrogen.
This makes the leak far more noticeable; in fact, you can often hear it. For this reason, using dry nitrogen is a must when using audible leak detectors.
Supply House OpportunityWell, that's how nitrogen is used, or at least, how it should be used. So, where does your company come into the picture? As I said before, if you aren't selling nitrogen, you should be. If you offer it but don't sell much, perhaps you could put on a class about its proper use for your customers. Show some good examples of what happens when you don't use it. That would not only build good will for your company and improve the quality of installation and service work in your area, it would also serve to grow your sales and reduce warranty costs.
The biggest problem for a technician when it comes to using nitrogen is simply the weight of the cylinder. It is extremely heavy and hard to get up to high or into tight places. However, at a recent industry exhibition, I noticed one Canadian company that was offering a new light-weight aluminum cylinder. A good idea, but I don't remember the company's name. Anyway, even if you sell only the heavy cylinders, there is added profit in selling cylinder hand trucks.
Also, there are the sales of regulators, gages, and 1/4-inch refrigerant-hose adapters. Although it might be tempting for some technician or company to try to find a way of getting by without a regulator, that is extremely dangerous and should never be tried. The unregulated nitrogen pressure in a freshly refilled cylinder can blow up air-conditioner coils and cause injury and death. Never pressurize a system higher than 250-psi. Also, other gases should never be used. Explosions have been caused by using oxygen to pressure-test systems, due to the combustible reaction of the oxygen hitting hot compressor oil. And CO2 usually contains too much moisture to be introduced into a closed system.
I hope this primer has helped you to come to a better understanding of the vital uses for dry nitrogen in the HVACR business. Now, do something to try to stem the declining use of this gas in our industry. Offer the products, train your customers, and show that your company is in this business to benefit and grow our industry as a true partner.