On a tranquil, 140-acre campus in rural Maryland is the Sandy Spring Friends School, a private school known to be a community of scholars, performers, artists, and athletes who honor traditional values, including a commitment to environmental sustainability.

And so it fit that, during the past year, the school’s 600 students in K through 12th grade and 150 faculty and staff fully accepted and learned about the campus-wide HVAC retrofit as it unfolded during the past several months.

According to Delbert Leese, facility HVAC engineer, the boiler, chiller, and air-handling system at the school’s key year-round teaching facility were pampered with tender care. Bandage-type repairs were applied routinely, up to the point where they became so labor-intensive and energy-wasteful that school managers needed a mechanical exit plan.

According to the school’s headmaster, the school is a debate-driven community that is respectful of difference. “We celebrate being a marketplace of ideas while providing a safe place to explore new concepts” in education, a tradition that spans the school’s 50 years of dedication to student learning.

Yet, when Leese and the school’s director of facilities turned their attention to the need for campus-wide HVAC upgrades, the debate-driven description didn’t exactly apply. “Of course, we looked at all of our options for the necessary HVAC upgrades that were long overdue, but there wasn’t much debate when we focused on the technology that best met the school’s needs, balancing that with the reality of a budget that had to be adhered to as well,” said Leese.

“The HVAC renovations at the main teaching facility and other buildings were much needed, and we were wasting time and resources in our latest attempts to keep the systems operating,” added Leese. “Sure, we considered the possibility of replacing the central heating and cooling systems, but that was likely to evolve into more of the same problem and at much higher cost.”

Tim Lawrence, sales associate for wholesale distributor R. E. Michel, explained that Leese invited him and Ken Herne, sales representative with the manufacturer’s rep firm, Landover, Md.-based Harry Eklof & Associates Inc., to see the school’s 4,000-square-foot, 17-room teaching facility, the building in greatest need of an HVAC solution.

“The building is in use year-round, so it was quickly apparent that their biggest concern was the inability to shut down the building for a two-month overhaul to the central systems,” said Lawrence. “They were unable to even consider it an option.”

Lawrence and Herne left with the challenge to develop an HVAC solution that would permit the facility to remain in use, even during the needed mechanical overhaul. “We studied the building’s layout, heat load, and cfms,” added Lawrence.

When Lawrence and Herne returned to the school to present their plan, they met with Leese. The recommendation: to use multizone mini-split heat pumps for the teaching facility. As it turned out later, several other buildings on campus, also in need of mechanical solutions, appeared to be an ideal fit for the use of multizone mini-splits systems.

“With about 3,500 configurations, Fujitsu’s selection of light commercial systems offers a broad range of air delivery options, including wall-mount units, ceiling cassettes and slim ducts to ceiling registers, so we recommended Fujitsu systems,” said Lawrence.

The final decision by school managers was the selection of Fujitsu’s Halcyon Hybrid Flex systems. The benefits included lower replacement cost, the ability to install systems while the school was in operation, high SEER and EER ratings, and the advantage of modulating operation — using only the energy needed to heat or cool interior spaces.

According to Lawrence, the R-410A multizone systems that they recommended and were later chosen by school managers include the up to 17 SEER Halcyon Hybrid Flex Inverter (HFI) heat pump line, a cross between VRF (variable refrigerant flow) and multizone technology.

“Contractors can select 18-, 24-, 36- or 48,000-Btu condensing units combined with wall-mounted, cassette, or slim duct indoor units,” he said. “Also, their HFI lineup now offers 7-, 9-, 12-, 18- and 24,000-Btu wall-mount units; 9-, 12-, and 18,000-Btu cassette units; and 9-, 12-, 18-, and 24,000-Btu concealed ceiling units — all of which can connect to a single outdoor unit.”

The manufacturer’s HFI systems also permit up to eight indoor units to connect to a single outdoor condensing system, and provide connectible capacity from 80 to 130 percent, or from 14,000 to 62,000 Btu.

“We chose to go with the Fujitsu Hybrid Flex inverter multizone heat pumps for several reasons, but chiefly because of the high efficiencies and lower operating cost, the many options we had for air delivery and, most importantly, because the teaching facility building could be in use the entire time, even in the midst of new system installations,” said Leese. “We could also join the multizone systems in a way that gave us redundancy, so if for any reason one system wasn’t operating, one of the other units could meet the need for heating or cooling.”

All room air handlers/evaporators were installed to permit redundancy. Each room has two separate units to allow system modulation down to less than 10 percent of their combined capacity to greatly reduce energy consumption. And by their redundant opposite compressors connections, one air handler is always available to maintain temperature control so that all spaces may remain in use if a system fails.

Leese added that other advantages with the multizone approach included lower replacement cost, and that the systems could be installed while the school was in full operation. “We also received the highest SEER and EER available for their application, and each room fully modulates to only use energy as it’s needed to heat or cool the spaces,” said Lawrence.

The teaching facility is one of 25 buildings on the school’s campus. Nine 18 SEER condensing units were installed there by Leese and his staff, now serving a variety of indoor systems air handlers: wall-mounted evaporator units, ceiling cassettes, and concealed duct registers. The installations were completed on a room-by-room basis.

“The students and parents had no idea we were making the changes,” said Leese. “It was an ideal arrangement that allowed the existing central equipment to work as needed, and for the new systems to come on-line as they were ready. We did a lot of the installations during evening and weekend hours, though there were times when we were working on the systems while students were in class. The work went well and was unobtrusive.”

The mini-splits were 48,000-Btu
multizone systems, though the building’s computer room was served by a 30,000-Btu single-zone unit, all installed by the school’s maintenance staff, directed by Leese. “There were no shutdowns during the entire installation,” said Leese. “That was the most important need.”

Leese and his staff installed 10 multizone condensing units and 10 branch boxes that now supply 29 evaporator units in the teaching facility classrooms. All of the condensing units were in grassy areas, so the decision was made to raise them off the ground on Airtec wall brackets to keep them away from leaves, grass, and snow. The linesets and electric wires were covered by slim ducts, making them less obtrusive. All the indoor units are controlled by remote control, ensuring the efficiency and preventing units being left operating when not needed.

“We’re now looking at a similar need for mini-splits at one of the dormitories, another facility we can’t shut down,” added Leese. “We expect to keep the existing boiler and radiators for back-up heat. But there’s currently no provision for air conditioning, and they could certainly use it. We’re excited about how easily we can provide year-round comfort conditioning to additional buildings.”

Publication date: 3/5/2012