The Florida State University satellite chiller plant provides chilled water for air conditioning needs on campus.

TALLAHASSEE, Fla. - Florida State University (FSU) is a campus of almost 500 acres. Located in Tallahassee, FSU has grown in recent years with the addition of new buildings. To support its expanded HVAC load, in 2008 the school built a new satellite chiller plant.

Located close by FSU’s medical school, the satellite chiller plant is connected to the central energy plant and serves as a “stage” plant to provide chilled water for air conditioning needs on campus. It is connected through a 1.5-mile underground piping loop. The plant is equipped with three 1,500-ton, 200-hp Trane centrifugal chillers (plus one backup), six 200-hp Taco TA pumps (four in operation and two held in reserve for future chiller additions), multi-purpose valves, suction diffusers, a CA expansion tank, ABB VFD units to control the pumps, and a custom-built Taco 4900 Series Air-Dirt Separator.

As a factory representative for commercial systems, Florida Hydronics of Jacksonville has a long history of association with both FSU and Vause Mechanical, a Tallahassee contractor. Florida Hydronics was instrumental in introducing the 4900 Series and its capabilities to the school’s utilties team. Conventional separators had failed to keep up with dirt and sand in the school’s HVAC system, so the school was looking for a more capable unit for the new satellite chiller plant.

Vause Mechanical installed the custom Taco 4900 Series system in the plant. According to Keith Vause, a self-described “Taco man through and through,” the FSU 4900 was the biggest air separator his company had ever installed - and Vause Mechanical has installed thousands of these units over the years.

“It’s a monster,” Vause said. Because of its sheer size, the 4900 was delivered and installed when the chiller plant slab had been laid and the building shell was still open.

The custom Taco 4900 Series system has a 30-inch inlet pipe diameter and will handle up to 19,200 gpm when the entire plant is operating at full capacity. However, the 4900 Series unit actually operates more effectively at part load conditions because the lower flow rates allow for greater air and dirt removal. The 4900 is installed in a variable flow system, which can handle flow rates of 3,200 (pump design) x 6 because of the six pumps.

FSU’s custom-built Taco 4900 Series Air-Dirt Separator will handle up to 19,200 gpm when the entire plant is operating at full capacity.

The 4900 unit features integral Pall ring technology, which Taco has patented for use in hydronic air separation. Pall rings are used in the processing industry to mix gases with, or to separate gases from, liquids. Taco employed Pall ring technology in its air separators to clear the system of microbubbles, sand, dirt, and corrosive rust. While air bubbles are separated by the Pall rings through a process known as coalescence, dirt particles get caught and sifted to the bottom of the tank where they can be removed through a blow down valve. A flushing cock allows the Pall rings to be cleaned for maintenance purposes, and the ring basket can be removed from the unit by one person on units with removable covers.

The 4900 Series, which was designed and constructed to ASME code, is available in both air and air-dirt models. The FSU satellite chiller plant required an air-dirt version.

The mechanical room holds six 200-hp Taco TA pumps. Four are in operation and two are held in reserve for future chiller additions.

Robert Vaughan, the school’s utilities superintendent, reported that the unit gets quite a regular workout. “Several months after installation,” he said, “the unit was blown down for the first time and three wheelbarrows of sand were removed from the separator.” The large amount collected was the result of an in-rush of sand into the 4900 Series, where previously sand had collected in various parts of the system.

“We perform a weekly blow down and continue to remove a significant amount of sand and dirt each time,” Vaughan said. “This sand and dirt used to typically get clogged in strainers, air handlers, valves, etc. But there has been a significant reduction in maintenance calls because now we have a central point of cleaning. We’ve been very impressed with the performance of our 4900 Series unit. It works great.”

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Publication date: 10/11/2010