Issue

The Robert E. David building, a six-story state office building in Columbia, South Carolina, was due for an energy-saving upgrade. The South Carolina Department of Employment and Workforce sought to make improvements to the 1975-built David building, which houses its administrative headquarters.

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 Energy managers at the South Carolina agency saw an opportunity to reduce the building’s energy usage with a renovation that included upgrades to allow for more energy-efficient lighting, HVAC, and building controls. The HVAC upgrade required replacing the building’s 40-year-old two-pipe, centrifugal water-cooled chiller system. The upgrade also required a flexible workhorse given the region’s humid, subtropical climate, which calls for air conditioning much of the year and flexibility to deliver heat during the chill of winter months.

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Mechanical Design, Inc. (MDI), the mechanical engineering firm on the project, provided engineering services for the replacement of the chiller, chilled-water pumps, condenser-water pumps, and all related piping. “Most state office buildings have hot-water heat and this building relies on electric strip heaters for warm air. One key objective of the separate controls upgrade was to avoid the use of simultaneous heating and cooling,” says Danny Wilds, P.E., LEEP AP, president of MDI in Columbia, SC.

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“The customer was looking for high energy-efficiency and low sound in a replacement chiller as noise was a consideration since the mechanical room is located above executive offices,” says Todd Woodrow, Daikin Applied representative and sales engineer at Hoffman & Hoffman, Inc. in Cayce, SC.

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Solution

The process to vet chiller manufacturers and specific products began in 2012. “The customer was looking for the chiller with the best lifecycle cost over a 20-year period of operation,” Wilds says, adding the specification process also required the new chiller to meet a noise threshold of 81.5 dBA.

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Among a number of manufacturers considered, hands down, Daikin beat out the competition with its Magnitude magnetic-bearing chiller, on a lifecycle-cost basis. The award-winning Magnitude chiller renders part-load performance of .32 kW/ton IPLV and sound pressure ratings as low as 76 dBA. “The Magnitude chiller hardly ever has to run at full capacity and the part-load efficiency (of .32 IPV) was taken into account for our firm to calculate cost on weighted averages of operation throughout the year,” Wilds says.

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“From the chiller standpoint, using a magnetic-bearing chiller is unique. The renovation also brought the ability to better control the electric heat which also contributes to significant energy savings for the owner,” Wilds says. The controllers in the variable air volume (VAV) boxes that modulate cool air were also replaced as part of a separate contract.

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