Efficiency Standards Prompt Rooftop Innovations
ECM fans, DOAS units emerging as preferred options
More than half of U.S. commercial building space is cooled by packaged HVAC equipment, according to the U.S. Department of Energy (DOE). So it comes as no surprise that energy efficiency is the biggest trend driving the rooftop market.
“Manufacturers are emphasizing energy efficiency by offering components that provide customers a greater range of operability,” said Ross Miglio, president of ClimaCool Corp. “Some of these features include ECM [electronically commutated motor] fans, options for energy recovery, and configured rooftop systems designed for 100 percent outdoor air treatment [dedicated outdoor air systems]. Furthermore, ultra-quiet, highly efficient variable capacity compressors contribute to lower operating sound levels and provide exceptional energy efficiency while minimizing operating costs.”
Dedicated outdoor air systems (DOAS) have become more prevalent in designs for commercial HVAC equipment as of late, noted Richard Boothman, director of North American sales, Modine Mfg. Co.
“The average end user has become more aware of the need for proper ventilation,” Boothman said. “Also, building owners and managers are becoming aware that ventilation equipment provides fresh air while also dehumidifying outside air. This helps them avoid issues like sick building syndrome and greatly reduces the risk of mold growth. When compared to typical packaged rooftop units, DOAS units often have larger/deeper DX coils to handle the difficult latent loads and can provide higher temperature rises in heating. They also provide a wide modulation range in both heating and cooling modes and offer sophisticated controls.”
Modine’s Atherion DOAS unit features digital scroll compressors, a microchannel condenser coil, an electronic expansion valve [EEV], and modulating hot gas reheat to properly cool and dehumidify outside air, according to Boothman. “The Atherion also can be specified with a high-efficiency gas furnace section with thermal efficiencies at or above 90 percent.”
Mike Ray, director, commercial rooftops, Lennox Commercial, agreed, saying energy efficiency is driving the rooftop market toward additional technology and innovation, which increases customer savings from the total cost of ownership.
“Lennox’s Energence Ultra-High-Efficiency units provide energy savings, intelligence, sound reduction, and time-saving serviceability,” Ray said. “Eight of these rooftop models in 3-20 ton meet or exceed 20 SEER or IEER and exceed ASHRAE 90.1 2010 by as much as 96 percent. Featuring the Prodigy® 2.0 Control System, they assist the contractor and servicer with speed of installation and service, which is highlighted by an easy-to-navigate setup plus service information, which is communicated to the technician.”
Chris Stocker, product manager, Commercial Rooftops & Condensing Units, Daikin Applied, said variable speed technology is “the game changer” going forward.
“It allows you to maintain tight temperature and humidity control, while avoiding both overshoot and undershoot typically seen with staged compression,” he explained. “Electronically commutated motor (ECM) technology now provides manufacturers with a cost effective way to provide better energy efficiency across the operating ranges of both supply and exhaust fans, in addition to being able to better control effective building pressurization. ECM fans also allow manufacturers to tightly control the lift across the condenser coil, which is similar to a past trend when VFDs were starting to be added to cooling towers on water-cooled chiller plants.”
Daikin Applied’s premium efficiency Rebel commercial rooftop unit is built on a customizable platform that encompasses technologically advanced components that contribute to efficiencies surpassing ASHRAE’s 90.1 by 95 percent, Stocker said.
“Daikin leads the industry in variable speed compression [via VRV technology] and this has carried over into our Rebel product line — the first to meet and exceed the DOE’s High Performance Rooftop Challenge.”
OTHER MARKET INFLUENCERS
Bryan Ware, portfolio leader, light commercial package products, Trane, said the general rooftop market is relatively stronger than it has been in several years.
“New construction is recovering and starting to come back. It’s beginning to rival the replacement piece of the business,” he said. “That’s a positive sign for the industry. And Trane has always been focused on being able to serve customers in multiple ways. We provide entry-level, minimum-efficiency products; a tiered efficiency level product, and we have ultra-premium-efficiency products for more sophisticated customers looking for triple bottom line, better energy consumption, sustainability, and better comfort.”
Trane’s Precedent™ light commercial rooftop units feature eFlex™ variable-speed compressors and fans, which precisely match output to the cooling demands of the space for exceptional EER and IEER.
“It’s a triple-variable product with a variable-speed indoor fan, variable-speed outdoor fan, and variable-speed compressor capacity,” Ware noted. “So, we’re able to give the ultimate performance for the right building load as well as the right comfort level.”
Chris Opie, marketing director, commercial systems, Carrier Corp., said one notable trend in the current rooftop market is the replacement of existing units. “While many of these replacements are due to rooftop units that are past their useful lifespans, several early retirement utility rebate programs are being offered by energy providers to incentivize clients to replace their older units with newer, more efficient models.”
Carrier offers multiple replacement solutions, from standard-efficiency products up to 21-IEER ratings on its 3-23 ton WeatherExpert™ rooftop units, Opie noted.
Improved serviceability is another important trend in the marketplace, according to Kevin Stockton, product manager, TempMaster®, Applied DX, Johnson Controls Inc.
“Improved serviceability is important, particularly as older rooftop units are now in need of service,” he said. “Ease of service is critical in new rooftop designs. Equally important is connectivity, making rooftop units part of the entire heating and cooling system and contributing to a smart system. Diagnostic capabilities and the ability to detect problems improve with connectivity, as does system efficiency. We’re also seeing new technologies related to fans, filtration, and compressors that are shaping the rooftop market, integrating what used to be advanced features as standard features in rooftop units.”
Johnson Controls’ TempMaster® OmniElite™ rooftop unit features hot gas reheat, which enables it to meet new demands for comfort and efficiency by dehumidifying the air. Efficiency ratings exceed ASHRAE 90.1 standards, and the system offers a compact footprint that is up to 20 percent smaller than competing units, Stockton noted.
Additionally, Johnson Controls’ York® Direct Fit™ rooftop replacement solution is designed to directly replace existing rooftop units from other manufacturers. The exact-fit replacement design reduces installation time, cost, and complexity by eliminating the need for a curb adapter.
IMPENDING HISTORIC STANDARDS
The U.S. Department of Energy (DOE) announced new efficiency standards for commercial air conditioners and furnaces late last year. Developed with input from industry, utility, and environmental groups, these standards are expected to more energy than any other standard issued by the DOE to date.
These standards will occur in two phases. The first phase will begin in 2018 and will deliver a 13 percent efficiency improvement in products. Five years later, an additional 15 percent increase in efficiency is required for new commercial units. Over the lifetime of the products, businesses will save $167 billion on their utility bills, and carbon pollution will be reduced by 885 million metric tons, according to the DOE.
Eric Newberg, director, commercial product management, unitary products group, Johnson Controls, said many states are adopting new building codes based on the 2015 International Energy Conservation Code (IECC) and ASHRAE 90.1-2013.
“This has the net effect of implementing the 2018 efficiency requirements at a much earlier date,” he said. “The impact of the new building codes includes more than just unit efficiency. There are changes to fan control, unit staging, and ventilation that have to be addressed. Additionally, the new DOE standards will have a cost impact on rooftop units, which will increase the price to the market. There will be a large increase in use of variable frequency drives [VFDs] to control multi-speed fan requirements and higher IEER values. This increases the operational complexity of equipment and the application of the equipment, which will also impact the HVAC service industry.”
Because of the market being driven by ASHRAE 90.1 and DOE regulations, rooftop manufacturers are conducting thorough technology reviews to ensure they’re designing competitive systems, according to Eric Walthall, marketing manager, Danfoss.
“Rooftop OEMs will rely on innovative, optimized components that provide superior part-load performance and capacity modulation, including compressors, expansion devices, heat exchangers, and variable-speed drives,” Walthall said. “Step one of the DOE regulation adopts the ASHRAE 90.1 2016 IEER levels and goes into effect Jan.1, 2018 — demanding a faster response time by industry than the typical state-by-state adoption and implementation process of ASHRAE 90.1. Step two goes into effect in 2023 and will likely drive further system redesigns. This could cause constraints on existing testing facilities and engineering resources to support these changes, but it also presents a tremendous opportunity for investment as we shift to a more energy-productive industry.
“To meet the latest regulations and standards, rooftop units can employ tandem compressors; part-load, optimized, or fixed-speed compressor technology; as well as variable-speed compressor technology,” he continued. “Adding variable-speed drives to supply and condensing fan motors also will improve part-load performance tremendously. Danfoss is developing intermediate discharge valve (IDV) technology for scroll compressors that avoids over-compression and extra effort by the motor during part-load operation, thus significantly reducing energy consumption in rooftop units. Danfoss’s DSH and DCJ scroll compressors with IDV are backward-compatible for the new design of rooftops with fixed-speed scroll compression technology, meaning minimal redesign and implementation costs are necessary.”
Danfoss is also investing in an Application Development Center, a state-of-the-art laboratory and testing facility that will help the industry prepare to meet higher energy-efficiency levels and low-GWP refrigerant targets, Walthall noted. The center will be able to test residential air conditioning systems and rooftop units from 2.5-50 ton and air-cooled chillers sized up to 300 ton.
Opie noted that the standards will reduce electrical consumption for commercial buildings. “We anticipate the insertion of new technology that emphasizes compressor and fan-staging optimization. Such technology is already a standard feature on some systems and can be included as a factory add-on option in other systems. By optimizing these components to more efficiently support part-load operation, clients can take advantage of reduced electrical consumption. Additionally, as the technology is enhanced to provide more efficient systems, applications that have historically been designed as chilled waters systems are expanding their equipment designs to incorporate rooftops units.”
Miglio also noted the new efficiency standards will likely increase prices in the short term as manufacturers focus on redesigning their units to meet the requirements. “However, in the long term, customers should expect to see increased energy savings as a result.”
ClimaCool’s configured packaged rooftop systems offer a robust solution for commercial project demands from 6-90 ton and already meet new DOE rooftop standards. The systems provide notable application flexibility for air-cooled cooling, air-cooled heat pump, geothermal heat pump, water-source heat pump, and chilled water direct-expansion air-handler applications while offering a clear solution for dehumidification, heat recovery, heating, cooling, makeup air, and air quality and controls applications.
“There is a broad base of customers who apply unitary commercial equipment in different ways, but a big side of the market tends to be minimum-efficiency levels,” said Ware. “That is only going to get better for us from an energy perspective as new regulations tend to come in and start prodding customers to a higher energy standard.”
While nobody can predict the future, it’s easy to see that efficiency standards and regulations are pacing the rooftop market.
“For the standard-efficiency, high-volume rooftop segment, we expect to see a significant portion of those units to move to tandem design bases,” Walthall said. “At the same time, the high-efficiency, low-volume market will start to expand rapidly through the efforts of many industry energy-efficiency initiatives. In the long-term, the next generation of rooftops will transition to low-GWP flammable refrigerants, which will require the industry to overcome safety and building code obstacles.”
Ray predicts advancements in technology in variable-speed motors, variable-speed compressors, and additional controls to operate these technologies, as well as tools to make service and diagnostics quicker and easier. “As new technicians enter the industry, they will expect to be able to have the unit communicate details about how to get the system to return to full functionality. With the Prodigy® 2.0, which is standard in our Energence models, we provide a significant amount of information to assist the technician in servicing the system.”
Opie said there will also be an increased focus on IAQ going forward. “We expect additional attention in IAQ, which will place additional emphasis on economizer usage, demand-controlled ventilation, energy recovery, and higher outdoor air applications. Improved indoor environmental quality can have measurable benefits in schools and workplaces. A recent study by Harvard University, SUNY Upstate Medical University and Syracuse University found that improved indoor environmental quality doubled participants’ scores on cognitive function tests.”
“Regardless of the DOE and other regulatory things, most of the customer base is looking for a better, more comfortable building that performs more efficiently and doesn’t cost as much to operate,” Ware said. “In general, the industry is going to continue to drive toward simple energy efficiency. Additionally, in the long term, as owners get more focused and become savvier in managing their facilities and managing the comfort of the folks in their buildings, we’ll see some focus on innovations come to light around controlling the system. These are all positive things driving the future of our industry forward in my mind.”
Publication date: 6/13/2016