The expansive, yet graceful Acacia Court Building in Stockton, California, originally a state hospital, has been given a new life. An extensive renovation has converted this 1920s, 100-yardlong concrete building into the campus showplace of California State University, Stanislaus-Stockton. Located in the 102-acre University Park, the building now houses faculty offices and classrooms for upper division and graduate courses.

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Here, students can complete their degrees—without commuting to the main campus in Turlock—in the mixed-use Magnolia District, redesigned as a "live, work, walk" neighborhood. The renovation draws on unique technology, including an HVAC system designed around a Magnitude magnetic bearing centrifugal chiller from Daikin—with impressive results. The chiller consumes far less power, costs less to operate, and generates far less noise than conventional chillers.

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In 2002, The Grupe Company, a respected California developer, was awarded the University Park contract to develop the area into classrooms, offices, shops, apartments and a community center. As many as 32 buildings were razed; 19 were renovated. Part of the goal was to keep floor plan changes to a minimum, primarily as a "renovate to suit" project.

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As part of a thorough evaluation, The Grupe Company determined that the HVAC system was high on the list of systems to be updated at Acacia Court. The existing system included two chiller units dating from the 1950s, and some of the piping for them had collapsed. "The efficiency of the old system was really poor," said Chris Rasmussen, with The Grupe Company's facility management department. "We explained to the university that the building needed a new chiller, along with new piping and a cooling tower."

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A new kind of chiller for an old building

The Daikin Magnitude chiller features magnetic bearing compressor technology that is oil free. This design significantly reduces sound levels, because the magnetic bearings eliminate the metal-to-metal contact noise of conventional bearings. Sound pressure ratings are as low as 77 dBA per ARI Standard 575. Energy performance is also revolutionary. The Daikin Magnitude centrifugal chiller operates as low as 0.375 kW/ton IPLV, the most efficient performance in its tonnage range in the industry. Full load performance is as low as 0.62 kW/ton—about 32 percent more efficient than screw compressor chillers. "The magnetic bearing technology of the Daikin Magnitude centrifugal chiller provides superior energy efficiency by eliminating the high friction losses of conventional centrifugal compressors," said Daryl Showalter, director of marketing Daikin chiller products.

"Variable frequency drives unload the chiller to 10 percent of full load. The chiller requires less than five amps to start, compared to 500 to 600 amps for a traditional screw compressor chiller. And, because magnetic bearings require no lubrication, there is no need for oil heaters, oil coolers, oil pumps or oil piping."

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"A Really Good Experience"

Despite the completely new technology and design, installation went smoothly. "We had a really good experience," said Rasmussen. "We completed 90 percent of the installation work with our own maintenance staff, which really helped reduce the cost," Rasmussen added. "And since the system went online, there has been zero unscheduled downtime because of problems, only scheduled downtime for a couple of software upgrades."

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The two compressors of the Magnitude chiller operate on a common refrigerant circuit, improving system reliability. In the event of a mechanical or electrical problem, one of the two compressors can continue to operate until repairs can be made. "If there is a problem with one compressor, we can still run with a 60 percent load on the other one," said Rasmussen.

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The MicroTech II® digital unit controller on the chiller effectively runs and monitors the chiller operation. "We currently run the chiller based on a time clock input because there's not as many maintenance issues with the magnetic bearing compressors.

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When the budget allows, we can integrate the MicroTech II chiller using BACnet®, LonTalk® or Modbus® protocol thanks to the Protocol Selectability^® feature of the unit controller."

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