In 2015, the U.S. Department of Energy (DOE) announced new efficiency standards for commercial air conditioners and furnaces that were negotiated with HVACR organizations and manufacturers as well as utilities and environmental groups. Touted as the largest energy-saving standards in history, they would save businesses $167 billion on their utility bills over the lifetime of the equipment, and reduce carbon pollution by 885 million metric tons, stated the DOE.

These new standards were to be implemented in two phases. The first phase took effect on January 1, 2018, and increased the minimum efficiency of commercial rooftop units (RTUs) by about 13 percent. The second phase will take place on January 1, 2023, and require an additional 15 percent increase in efficiency. RTUs represent a huge market in the U.S., cooling about half of the total commercial floor in applications that include schools, restaurants, big-box stores, and small office buildings.

Knowing that the two efficiency increases would come in relatively quick succession, RTU manufacturers were very proactive, and many already offer products that meet the 2023 standard.

GETTING READY

Most RTU manufacturers were well prepared to meet the DOE regulation in 2018, which involved incorporating energy-efficient features such as variable air volume (VAV) fan control, scroll compressors, electronically commutated motors (ECMs), and/or improved heat exchangers. The additional 15 percent increase in energy efficiency required by 2023 is a little more difficult to achieve.

“The challenge is to build a 2023 energy-efficient rooftop without significantly impacting the cost, size, and weight of the equipment,” said Matt Dodds, product manager of applied rooftops, Daikin Applied. “Daikin is addressing these challenges with its new, innovative cabinet designs and space-saving technologies like ECM fan arrays. These casing advantages will help us reduce the length and weight of equipment, which helps offset the size and weight impact from the larger coils required to meet 2023 efficiencies.”

In addition, many of Daikin’s rooftop offerings have been optimized for part-load energy efficiency through the incorporation of technologies such as inverter scroll compressors. Smarter refrigeration controls, including modulating head pressure control, also allow for more efficient refrigeration system operation at off-peak conditions, said Dodds.

Part-load energy efficiencies are of greater importance in new RTUs because in the new standard, DOE has replaced EER, which is the metric traditionally used to indicate energy efficiency, with IEER (integrated energy efficiency ratio).

“EER is the energy efficiency of equipment at full load, which only reflects the equipment performance during a limited portion of the year,” said Rosa Leal, senior product manager of commercial and residential packaged - AC division, Rheem. “A unit usually operates at part load, which is what IEER measures. Using IEER results in more accurate published ratings.”

There are definitely challenges associated with meeting the new energy efficiency standard, said J.T. Holtschlag, vice president and general manager – North America unitary, Carrier commercial HVAC. That’s because in order to reach the new efficiency levels while keeping all the customer requirements and benefits of RTUs intact, all aspects of system design will need to be precisely engineered. He sees compression, air management, heat transfer, and integrated controls as being the key to reaching the higher efficiency levels.

“The biggest challenge with meeting the 2023 deadline may be meeting other national, international, and regional requirements at the same time,” he said. “One example is the new UL standard 60335 that faces the industry today. We must also consider the activities associated with the phaseout of HFCs in these products. Although the overall picture is still a bit unclear, it is coming, and we all need to be ready.”

Testing new rooftops to ensure energy efficiency compliance may be another hurdle for RTU manufacturers, said Philip Smyth, director of product management, DX ducted systems, Johnson Controls. For this reason, the company has dedicated its Rooftop Center of Excellence in Norman, Oklahoma, to the pursuit of innovative manufacturing technologies, advanced testing capabilities, and new modeling and simulation tools to increase speed-to-market to meet customer demands.

“Our state-of-the-art facility features over 900,000 square feet of space that includes a two-story, 52-foot-high testing lab with the ability to test a 150-ton rooftop unit in temperatures ranging from minus 30º to 130ºF,” he said.

NOW AVAILABLE

While most manufacturers believe there will be no significant differences in the way 2023 regulation-ready rooftops will be installed or serviced, there will be some notable changes in the way they are designed — mainly, the components, controls, and technology used in these new RTUs will be more advanced, said Leal.

For example, Rheem’s new commercial platform, the Commercial Renaissance™, which meets the 2023 standard, includes the patent-pending SmartShield™ coil system and the CommandCore™ control system, which maintains optimal unit conditions at various load demands to boost overall efficiency and reliability.

“Additionally, the new 3- to 5-ton design comes standard with direct-drive ECMs for blower assemblies to further increase EER and IEER values, as well as included patent-pending heat exchangers, which provide a higher steady-state efficiency, all while maintaining competitive pricing,” said Leal.

Johnson Controls offers several product lines that already meet the 2023 standard. Its Premier™ 25- to 50-ton commercial RTUs achieve high efficiencies and reduced operational costs over the life of the unit. The company has also recently released a value-priced RTU that provides an economic path to meeting DOE standards. The YORK® Sun™ Choice 15- to 27.5-ton RTUs exceed 2023 DOE standards by 10 percent to reduce energy consumption and associated operating costs.

“Premier units not only exceed DOE regulations, they add value to the user and enhance the performance of the building,” said Smyth. “This includes installation flexibility, serviceability, and intelligent control. These high-performing RTUs can achieve a 50 percent higher-than-required efficiency (depending on the local code) to deliver outstanding cost savings over the lifetime of the unit.”

Many of Carrier’s WeatherMaster® and WeatherExpert® Series RTUs already meet the 2023 standard, and the company is also looking at intuitive new RTU designs, as well as integrating intelligent control platforms. A new refrigerant is also on the horizon, as Carrier has identified R-454B (Puron Advance™) as its primary lower-GWP solution to replace R-410A in all of its ducted residential and light commercial packaged solutions sold in North America.

“The new refrigerant will be offered in these Carrier products beginning in 2023, and it is expected to surpass the requirements of anticipated future regulations,” said Holtschlag. “With a GWP of 466 — one-fifth that of R-410A — Puron Advance refrigerant was selected as the best solution to minimize environmental impact and energy use, while improving performance, safety, and longevity. Carrier has worked closely with regulators and research groups to develop standards, codes, and regulations that will help ensure the safe use of R-454B.”

After comprehensive evaluation and testing, Daikin concluded that R-32 would be the ideal low-GWP alternative to R-410A for many key residential, light-commercial, and applied products in North America.

In choosing the new refrigerant, Daikin found that in comparison to R-410A, R-32 has a drastically lower GWP and could reduce refrigerant charge in certain equipment by up to 40 percent. The company took a holistic approach to find that equipment using R-32 can be more energy efficient and compact — thereby consuming fewer manufacturing resources — when compared to equipment using R-410A or certain alternative refrigerants.

“We believe that R-32 — a pure, single-component refrigerant available globally from multiple suppliers — is easier to reuse, reclaim, and recycle when compared to other refrigerants that are blends of R-32 and other components,” said Dodds.

Regarding efficiency requirements, most of Daikin’s products are already 2023-compliant, and they include the Rebel™ rooftop, which exceeds 2023 compliance from 3 to 28 tons, as well as the new Rebel Applied™ platform from 30 to 52 tons.

Just because RTU manufacturers are already able to meet DOE’s 2023 standard does not mean they are resting on their laurels. Indeed, they are continuing to innovate and prepare for the future, even if it is not clear what that may bring.

“The HVAC industry is ever evolving with a constant stream of new innovative technologies,” said Leal. “This innovation is driven by a combination of environmental sustainability, DOE policies, and regulatory legislation, as well as a highly competitive market. All of these factors are considerations that OEMs are constantly weighing and are our biggest challenges when developing products to service our customers.”

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