“Assuring the product is installed with the factory-issued, epoxy-coated coil — like those found in the Trane® Hyperion air handlers — or replacing it with an aftermarket Trane coil can reduce the callbacks and cleanings associated with this phenomenon,” said Gary Sapp, director of air handler and coils engineering, Ingersoll Rand. “The main improvement in coil technology, however, is the move to aluminum coils that prevent formicary-type corrosion leaks.”

Looking ahead in coil trends, Sapp explained that the future of coil technology brings into play brazeless connectors. Not only does it take the torch out of the process, he said, but it also lowers the probability for leaks when making connections. Taking the torch out is important according to Kirby Bicknell, director of a/c and heat pump engineering, Ingersoll Rand.

“Some city codes prohibit using a torch inside a home without a special permit,” he said.

Other reasons the brazeless connection is important relate to the labor shortage and future refrigerants.

David Garris, senior product manager for coils, Ingersoll Rand, explained that brazing is not something everyone can do.

“The shortage of technicians is an industrywide problem,” he said. “Brazeless connections simplify the installation process. If you don’t have to braze, it becomes an easier job.”

Sapp, Bicknell, and Garris agreed that contractors need to consider that the tooling and training of their teams will require instruction for making brazeless connections.

As for efficiency and refrigerant changes, Sapp said that brazeless connections will help installation practice changes that arise from future refrigerants. Looking beyond refrigerants, the company is continuing to strive toward greener measures.

“As we look for ways to be greener, we are seeking ways to have less charge in a system,” said Sapp. “Smaller coil tubes will help us use less charge.”

REFRIGERANT TECHNOLOGY BOOSTS

Smaller diameter tubes, like those found in coils using microgroove technology, allow for more cooling with less refrigerant charge, according to Nigel Cotton, microgroove team leader, International Copper Association.

“Globally, smaller-diameter, inner-grooved copper tubes are widely used in the air-conditioning marketplace, especially for room a/cs and PTACs,” he said. “The use of natural refrigerants is driving change in gas cooler use in industrial applications, and a high-strength copper-iron alloy is being adopted for use in gas coolers as well as refrigerant transmission lines.”

From his perspective, Cotton sees coil improvements driven significantly over the past decade in response to refrigerant changes.

“We have coils for use with R-32, HFOs, and low-GWP refrigerant blends,” he said. “Mildly flammable (A2L) refrigerants are being adopted globally, especially R-32, but it is not the final word on refrigerants.”

There are also microgroove coil applications for use with hydrocarbon refrigerants such as propane (R-290) and isobutane (R-600a). Employed in light commercial refrigeration, microgroove tubes allow for the same cooling capacity to be realized with a decreased amount of these flammable refrigerants.

“In May 2019, the approval of an increase in the charge limit for A3 (flammable) refrigerants to 500 grams from 150 grams in self-contained commercial refrigeration cabinets under International Electrotechnical Commission standard 60335-2-89 opens the door to the development of a broad range of atmospheric-friendly refrigeration equipment,” said Cotton, “especially when smaller-diameter copper tubes are used with propane as a refrigerant. Technicians will need to be prepared to service this new generation of refrigeration equipment.”

As the future of coils and refrigerants continue to evolve, Cotton is expecting the further development of copper-tube heat exchangers for use with R-744 refrigerant — CO₂. He said that this market is currently underdeveloped but that recent investment by component manufacturers in CO₂ technology signifies a quick reduction in component costs.

“Work continues on the application of smaller-diameter copper tubes along with high-strength copper alloys such as UNS C19400,” said Cotton. “Smaller-diameter tubes will be key to more compact and efficient coils for use in CO₂ gas coolers. Several companies in Europe are already offering these. Contractors in the U.S. will soon need to know how to service this type of system effectively.”

CREATIVE FLEXIBILTY

Coils and condensers will change as consumers demand higher efficiency and improved aesthetics from their HVAC systems. One way to accomplish this is with a flexible design, said Steve Hutchcraft, U.S. Strategy, Development, and Operations, Tadiran Holdings Ltd.

“As the demand for higher-efficiency systems continues to grow, I think we’re going to see a greater demand for multi-split-type systems — multiple indoor coils connected to a single outdoor inverter condenser,” he explained. “On the indoor side, the variety of offerings will expand significantly beyond the single, central, indoor A-coil and blower.”

Hutchcraft expects to see a growing array of soffit-style coils — both ducted and direct flow — as well as wall-mounted units and below-floor coils. According to him, space and efficiency are going to be the two main drivers impacting technology and design on the condenser side.

“Ironically, they are at odds with each other,” said Hutchcraft. “The more efficient the condenser, the larger it gets.”

He explained the significance of this in regard to increasing home sizes and decreasing lot sizes.

“With HOAs [Home Owner Associations] and fire codes restricting placement of condensers, the units are being forced into ever-smaller backyards,” said Hutchcraft. “That’s why a condenser like Tadiran’s Inviz — that can be installed within an enclosed space — seems to make so much sense. As the industry moves forward, I think we’ll see much more creativity with the condensing unit like we will with the coil.”

Publication date: 6/10/2019

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