A notable trend in HVAC and refrigeration is that contractors are increasingly repairing faulty aluminum coils and return bends rather than ordering new parts. Two factors are driving this change: supply chain breakdown and shorter manufacturer warranty periods.

While the supply chain issues seem to be easing a bit, it’s been a frustrating couple of years of long waits to get new parts and it’s been tough to keep them stocked. And obviously when equipment fails — especially in refrigeration — there's no time to wait for the weeks or months it could take to get a new part.

Even if new parts become more readily available, repair work will still be very much in demand. That’s because many manufacturers have reduced the length of their aluminum coil warranties, because they’ve found that a 10-year warranty isn’t viable when it comes to aluminum, which is a thin metal that can be easily damaged. Essentially manufacturers underestimated the volume of replacement parts they’d be sending out when they offered the long warranty.

Aluminum Alternative

Copper was the mainstay in HVAC and refrigeration coils until 2011, when copper prices went through the roof. Over the next several years, manufacturers began testing alternatives and the industry settled on aluminum as a workable, less costly option, although copper is still used in certain large commercial applications.

Brazing is typically the process that technicians use to repair aluminum coil leaks (see sidebar). Most contractors have been trained to braze copper tubes, but brazing aluminum is a very different proposition, and contractors need to understand the differences.

While aluminum is considerably cheaper than copper, it poses some issues. For example, when doing repair work, it’s very easy to further dent or gouge the refrigerant coils, which understandably makes contractors nervous.

Aluminum also has a lower range of heat tolerance for brazing, melting at a much lower temperature than brass or copper. Field technicians need to pay close attention to the flame temperature to avoid a meltdown, or worse, irreparable damage to the part.

Another complication: unlike copper that changes color as it gets hotter, aluminum gives no physical hints.

With all these challenges, education and training in aluminum brazing is critical. Most seasoned techs have not been taught how to braze aluminum because there was no need for it in the past. It's important for contractors to find organizations that offer this education. Some manufacturers provide free NATE-certified training — for example my team and I conduct brazing classes for technicians who install and repair equipment — and many are now regularly asking for information and instruction on brazing to repair leaking aluminum coils. Trade and technical schools may offer the training as well, although fees would likely apply.

Brazing Kits

All that is needed for aluminum coil repair work is a brazing torch plus the proper alloys and brushes. Portable brazing kits designed specifically for aluminum repairs are now available and may include mini tubes of flux-cored alloys and brushes and a storage pouch that can attach to a belt loop.

Many brazers use an oxy acetylene torch, which has a very hot flame, so technicians need to have good control of the heat, including keeping the flame further from the metal than they would with copper. The main goal is to melt the alloy out but not melt the base metal.

More and more techs are starting to switch to lightweight hand torches using MAP-pro gas. Made up of 99.5% propylene and 0.5% propane, it is a good low-temperature option. The one-pound gas cylinder is easy to carry around on a job site, which is especially important in tricky applications like a rooftop unit that requires climbing a ladder. MAP-pro cylinders are usually mounted with a 12-inch torch and can be easily maneuvered around the equipment being repaired.

This approach is also a low-cost option. Torches are $50 or less, tubes of aluminum alloys are about $17 (versus 15% copper alloys at $100-plus), and a tank of MAP-pro gas from a wholesaler is approximately $10. The gas is extremely flammable, though, so caution when handling it is strongly advised.

With the proper tools and training, technicians will save valuable time by being able to identify a damaged coil on site and complete the repair job on the same visit. Plus, repair work is an opportunity for contractors to earn additional revenue, so they’ll want to make sure staff can do it well.