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As standards developers regularly increase the minimum energy-efficiency requirements for rooftop units (RTUs) and air handlers, manufacturers are working to meet — and often far exceed — those standards. By incorporating increased motor efficiency, design improvements, and the utilization of energy recovery options, manufacturers are producing units that are more efficient, intelligent, and connected than ever before.
No More Energy Hogs
Eric Taylor, marketing manager at AAON, said the efficiency of rooftop units and air handlers has greatly improved just in the past few years.
“We have introduced high-efficiency air-cooled microchannel condenser coils, multiple variable-capacity compressor options, variable-speed direct-drive backward curved plenum fans, and standard 2-inch double-wall rigid polyurethane foam-injected cabinet construction,” Taylor said. “The features have improved both the full-load [EER] and part-load [SEER/IEER] efficiency of the AAON units. These same features have been introduced into AAON handling units for high-efficiency hydronic or DX split-system heating and cooling configurations.”
Daikin Applied has also made changes over the past few years to exceed the changing efficiency standards. Marketing manager Skip Ernst said the ASHRAE/ANSI Standard 90.1 minimum EER standard “increased about 5 percent in 2010, and our goal at Daikin was, and always is, to exceed those EERs across the entire Daikin product line.”
Ernst added that Daikin began including a factory-installed energy recovery wheel option for the RoofPak™ in 2001. “Over the past several years, the factory-installed option has also been incorporated into Maverick™ II and Rebel commercial rooftop units, and in 2013, we began featuring VFD [variable-frequency drive] compressors as a standard component on all Rebel units, instead of an option.”
Mike Ray, senior product manager, commercial rooftops, Lennox Intl., said the company recently introduced the Energence® ultra high-efficiency rooftop unit, which exceeds current efficiency standards and “was designed based on customer feedback, as Lennox stressed the importance of efficiency, total cost of ownership, and backward compatibility.”
Modine Mfg. Co., which has achieved decades of success with its Airedale school systems, entered the market in 2011 with the Atherion® packaged rooftop ventilation unit. Though the company has improved the function and efficiency of the Airedale systems numerous times over the past three decades, Joe Ellison, engineered product sales manager at Modine, said the Atherion “has yet to go through such cycles.” He added, “Five years from now, that might be a different story as we look to direct-drive ECM supply fans, compressor redesigns, refrigeration circuit changes, and many other new technological changes that could identify themselves in that time.”
Carrol Basham, commercial product manager at Rheem Mfg. Co., agreed that the efficiencies of RTUs and air handlers are continually improving.
“We have standard-efficiency units to meet market requirements, but we also have several high-efficiency offerings, and we’re always looking for ways to improve the efficiency levels of our RTUs,” Basham said. “We’re seeing more high-efficiency installations in new construction and in certain markets that have building requirements that need high-efficiency systems.”
Matt Muhlada, product manager for large rooftop units at Trane, a brand of Ingersoll Rand, said the current excitement over high-efficiency equipment has to do with an increasingly better return on investment (ROI), which entices consumers to purchase high-efficiency units.
“In the retrofit market, it is important that units are designed to fit the footprint of older models and competitive units,” he added. “This eliminates the need to purchase a curb adapter, which can add $1,000-$2,500 to the upfront cost.”
While rooftop units have changed and adapted, so have the tools used to install and service them. Dale Johansen, of Portable Crane, said the company’s first crane “was hastily built to immediately fill a need — to protect our own service technicians from injury.”
While the first design was crude, “it was a lot safer than using a rope to drag compressors up ladders to the roof,” Johansen said. Now, after four prototypes and much testing, the current product “has been tested to over 600 pounds and transfers all the weight to the ladder rail, not the rungs, as it was in all previous versions.”
To help save energy while improving IAQ, many RTU manufacturers have begun incorporating energy recovery ventilators (ERVs) for pretreating outside air, either as a standard feature or an add-on option.
“Energy recovery technology is becoming more and more popular as building owners and facility managers become aware that they can see a faster return on their equipment investment by implementing the technology,” Ernst said. “Daikin believes the HVAC market is anxiously waiting for VFD compressor control, and that constant volume control is being replaced by single-zone VAV [variable air volume] control.”
Ellison also said he has seen energy recovery modules gain popularity over the last couple of years. “With the ever-increasing need to conserve energy and make large HVAC investments as efficient as possible, one of the best ways this can be done is through the inclusion of an energy-recovery module to the main system,” he explained. “High-efficiency heating is also beginning to grow now that end users and engineers realize there are manufacturers out there like Modine that have such an option available.”
The use of VFDs and ECMs has also driven efficiency improvements over the past few years, Taylor said. “Nearly every AAON unit sold today includes at least one variable-speed fan,” he said. “Engineers, contractors, and building owners have seen the energy savings possible with these variable-airflow systems. When variable-speed fans are combined with a variable-capacity compressor system, this allows for a packaged, single-zone VAV configuration. Single-zone VAV units are the most energy-efficient heating and cooling systems available today.”
In addition to meeting improved efficiency standards, manufacturers are meeting consumers’ demands for a comfortable, healthy indoor environment.
“Humidity control has gained popularity recently,” Basham said. “In fact, Rheem has seen tremendous growth with HumidiDry™, a dehumidification solution that keeps humidity levels constant, even when there’s little or no demand for air conditioning. This technology gives business owners independent control of temperature and humidity.”
“Air cleaning has become more important with the risk and liability for health care organizations, the desire to keep children healthy and in school, and the need to eliminate smoke and odor from many spaces,” added Bryan Elser, product manager for catalog AHU products, Trane.
On the contractor side, there is also an increasing demand for improved serviceability, Ray said. “Many national accounts have their own service personnel teams, and they emphasized the importance of making service quicker and easier. The same can be said for our contractors, where less time spent on the job helps save them both time and money,” Ray said. “The Energence and Landmark families feature isolated compressors, a slide-out blower, and easily accessed gas heat compartment, all for quicker and easier servicing of the system.”
Options Become Standard
While technological improvements continue to drive efficiency, many of the features that used to be optional are becoming standard on many air handlers.
“The line between ‘custom’ and ‘cataloged’ has blurred as the cataloged manufacturers are offering numerous custom features and options that were only available from custom manufacturers five to 10 years ago,” Elser said. “This is great for customers because they’re getting a high-quality, robust unit with the options they desire without having to pay a ‘custom’ price. This provides great value and minimizes risk when using a catalog product.”
Taylor said AAON’s direct-drive backward curved plenum fans “have become standard on AAON rooftop units and air-handling units … because of both the energy and service cost savings associated with not having fan belts.” He added that economizers have also started to become standard on rooftop units and air-handling units because of the potential for energy savings in most climates.
Ray agreed economizers are becoming a standard feature for packaged units 5 ton and larger. “The contractor or national account can order either the high-performance economizer or the standard-performance economizer — the high-performance economizer exceeds the rigorous ASHRAE 90.1 2010 standards and also exceeds California’s Title 24 standards.”
As the industry sets an increasingly higher bar for efficiency, Ellison said the industry “could begin to see high-efficiency heating becoming a forced standard in the future.”
Ernst said factory-installed supply, return, and exhaust fan VFDs on 10-20-ton units and larger are becoming standard, as is BAS [building automation system] communication. “We have offered these energy-saving features for many years, as well as airfoil fans, evaporative condensers, extra insulation, low leak dampers, modulating furnaces, and extra steps of capacity to increase and deliver cost-saving efficiencies that put money back into customers’ pockets.
Basham added coil protection, stainless steel heat exchangers, economizers, CO2 sensors, and smoke detectors to the growing list of options that are starting to become standard on rooftop units.
“Coil protection is becoming standard because buyers want to protect that coil from harsh environments like hail, strong winds, and anything that will reduce its efficiency,” Basham said. “Stainless steel heat exchangers are becoming a bigger part of the market because the environments that these rooftop units are put in can be harsh. … We have a 20-year warranty on our stainless steel heat exchangers in commercial applications. For safety reasons, and peace of mind, our customers are becoming more aware of the need for CO2 sensors and smoke detectors in commercial buildings.”
On the Horizon
So, what’s next for RTUs and air handlers? Ernst said to expect even higher efficiency standards in the next several years.
“The cost of energy and government regulations will keep raising the bar for efficiency,” he said. “Actual energy consumption is much more dependent on part-load efficiency than full-load efficiency, and we think the market will respond accordingly. The Daikin brand of HVAC products will lead in those efforts.”
“There are some regulatory changes for the commercial HVAC industry, which should take effect in 2016, when the industry will start measuring efficiency by IEER solutions instead of EER,” Basham said. “From our perspective, as a manufacturer, we will carefully plan our product development to meet this new need.”
“We expect the federal mandates for minimum energy-efficiency ratings to increase around 2017-2018,” Muhlada added. “This will impact all our product portfolios and force us to adjust and redesign our existing systems.”
Elser said fan technology will continue to advance in the next three to five years. “Direct-drive plenum [DDP] fans have continued to increase in popularity because they provide benefits that touch a lot of our customers. We see this trend continuing to the point that in a few years most fans that ship in AHUs [air-handling units] will be DDP.”
Changes may be coming to how equipment for these units is moved, as well. Johansen said that once the Portable Crane is familiar in the industry, more contractors and employers will gravitate toward it due to its ability to prevent employee injuries and improve efficiency. “The most common injuries in our industry are related to auto accidents and ladder usage. Straddling a roof hatch, or leaning out off a ladder platform and roping up a 100-pound compressor by hand just doesn’t meet the safety standards of today.”
Taylor said the rooftop unit and air-handling unit markets are heading toward single-zone VAV as the standard configuration for nearly every application. “This is because of the potential for fan energy savings throughout the year compared with constant-volume systems,” he said.
In addition to improved efficiency and comfort, Muhlada said RTUs and AHUs are going to become increasingly connected over the next few years. “We are committed to developing wireless control options for light and large commercial rooftop units,” he said. “This makes it easier to install the system, move sensors placed in the wrong location, and communicate with multiple units. It makes the system faster to install and is more aesthetically pleasing than wired sensors.”
Ellison said evolving standards will continue to drive innovation and improvements in efficiency.
“These ‘changes’ could be based on geographic location, or just out of habits,” he said. “The majority of veteran building HVAC engineers are used to looking at EER as the gold standard when selecting equipment. Recent ASHRAE changes have moved IEER to the forefront as a more consistent method of measuring efficiency. Up next will be MRE [moisture removal efficiency], which will be critical in high-humidity areas of North America.
“It’s not known how much affect these changes will have, but make no mistake — they will change the way the industry is viewed.”
Publication date: 6/16/2014