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School District Does Its Homework, Chooses Variable Refrigerant Volume

July 1, 2016
The heat-recovery capability provides higher comfort levels with reduced tonnage and translates to significant energy savings.

Located north of St. Louis, in Florissant, Mo., Hazelwood School District includes 20 elementary schools, six middle schools, three large high schools, and three early childhood education locations—more than 30 buildings in all. The HVAC systems in most of the buildings were 15 to 25 years old, and maintenance costs were rising. Tom Mangogna and his district engineering staff felt there had to be more efficient systems on the market.

While attending product seminars sponsored by TMi Thermal Mechanics Inc. with Steve Limas of KAI Design & Build in St. Louis, Mangogna learned about the concept of variable refrigerant volume (VRV) and, specifically, the Daikin product. KAI, which had done work for the district, had experience with variable-refrigerant-flow (VRF)/VRV systems. Limas suggested Mangogna’s team investigate VRV for upcoming projects.

Daikin VRV ceiling-mounted Round Flow Cassette units.

“Daikin is at the forefront of efficiency and design flexibility,” Limas said. “VRV’s modulating compressor results in a more efficient refrigerant system, matching the load exactly and saving energy.”

KAI indicated Hazelwood could take advantage of building diversity using the heat-recovery capability, which would provide higher comfort levels with reduced tonnage and translate to significant energy savings. Mangogna and his engineering staff reviewed technical information and queried school districts—ones that had Daikin systems installed in buildings at least as large as Hazelwood’s for at least one year—around the country.

Daikin VRV heat-recovery condensing units.

“Our guys came away from those conversations saying we need to bring in this new technology, there are so many advantages,” Mangogna said. “Maintenance will go down, the energy savings are there, and teachers will have more flexibility to set their own temperatures. How do we move forward?”

After design and specification were complete, Mangogna had one set of conditions.

Trained technicians commissioning Daikin equipment.

“We wanted contractors experienced with the technology,” Mangogna said. “Bidding contractors had to show they had done multiple schools with equivalent square footage successfully. Even though the VRF/VRV technology had been in use worldwide for 30 years, we knew it was new to some contractors here. We didn’t want to be on their learning curve.”

Hazelwood now has 10 schools with Daikin air-cooled heat-recovery systems installed. In the case of Hazelwood Northwest Middle School, an energy- and maintenance-intensive 200-ton two-pipe system was replaced with a Daikin air-cooled heat-recovery system. The decision to use heat recovery allowed Limas to take advantage of shifting schedules to maximize energy savings.

“The reasons for going with these systems keep multiplying,” Mangogna said. “Our guys have all been trained in commissioning and servicing these systems, but they don’t have to spend a lot of time on them. The Daikin units are low-maintenance. They’re compact and so quiet—the teachers love that, and they can adjust their temperatures within a certain range that keeps our energy savings intact. And they really love that we no longer are either in heating or cooling mode. One teacher on the south side of the building who gets significant heat load from the sun may want to cool their room, while another teacher on the north side may want to heat their room, and this is now possible to do both heating and cooling at the same time, with the same system. We have reduced installed tonnage in some cases by close to 50 percent, with over 300,000 sq ft installed.”

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