"In early 1997, our new president asked, ‘What is on the top of your list of deferred maintenance items?' Without hesitating, I told him the air conditioning systems. That's how this started seven years ago, as we struggled to keep a hodgepodge of 30- to 45-year-old direct expansion [DX] and small chillers working."

To upgrade the aging systems, Mezzanini and his staff turned to Sodexho, an international facilities management and service firm, to evaluate campus physical plant priorities. "They came back to us and said the two most immediate needs were facility roofs and air conditioning." He noted that roof replacement was a fairly straightforward project, but more information was needed on the question of air conditioning.

Existing Systems

Most campus buildings had standalone cooling systems - both DX systems and chilled water - and many of those systems were old and quite inefficient. Further, there was an issue of reliability. "Systems had been added one building at a time, so there was no consistency. Many of the systems consisted of a single, small chiller. If that failed for any reason, the building lost cooling completely," he said.

"We've had a close relationship with Tampa Bay Trane for over 20 years, so we looked to them for help, and they gave us a lot of useful ideas," noted Mezzanini. "One that we began looking at very seriously was going to a central cooling plant. That would give us several benefits."

He indicated that the first benefit was that the university could then go to the most efficient chillers. "We knew that there was a lot more efficient equipment than what we were running."

Because of the diversity of the cooling load, the total capacity could be smaller than the sum of all the dispersed machinery the school was using. Finally, reliability would increase not only because new equipment would be installed, but because of redundant capacity. "If we lost one chiller," Mezzanini said, "we could still supply some chilled water to every building."

Another advantage of the central plant concept is that it allows the university to get along with its existing electric distribution system for a considerable time into the future. "Our system had become overburdened, particularly from all of this scattered air conditioning equipment," remarked physical plant director Jim Killmeyer.

With a central plant, a new electric service would be needed to that point only, and the rest of the electric system would be relieved of a good part of the load.

Mezzanini noted that the estimated cost of the new system was approximately $5 million, but that it came down to a choice of making this one-time investment, or continuing to budget every year for individual system replacements. The university's choice was that going to a central plant made the most sense.

Thus, with a detailed analysis of the costs and benefits of a central plant installation, the university initiated a plan to do the conversion, beginning in 2000. The new central cooling plant was sited in an addition to the existing central plant building. The equipment chosen was two Trane CenTraVacâ„¢ centrifugal chillers; a 400-ton Model CVHE and a 600-ton Model CVHF.

Another challenging part of the project involved burying chilled water lines throughout the campus. A challenge in this process was frequent encounters with other undocumented underground services. The workers found that many years ago, the recordkeeping on buried piping and cable was spotty. As a result they had to proceed cautiously. Ultimately, most of the central campus area received service.

With the startup of the central plant, the university was able to immediately retire an estimated 60 other cooling units, and thus reduce electric demand by 150 kW. According to Tampa Bay Trane's Doug Gillespie, chilled water goes to a variety of air handlers and fan-coil units in the different buildings. With the lower chilled water temperatures of the new chillers, one of the immediate benefits was much more effective dehumidification. Killmeyer noted that the campus has a master facility plan, and the chilled water piping was sized to allow future growth.

Another element in the conversion was the installation of a campus-wide Tracer Summitâ„¢ control system. Gillespie noted that the system allows the physical plant staff to closely observe conditions in individual buildings and even individual rooms to ensure that the comfort and efficiency goals are being met. Killmeyer and his staff can check conditions from numerous locations on campus, as well as from remote locations if necessary.

Mezzanini followed the installation of the central control system with interest, and was intrigued with the individual room comfort monitoring capability. Shortly after system startup, he noticed one room in one of the residential halls that was far out of spec for temperature with the rest of the hall.

"I decided to investigate personally, and when I got there, I found a student sitting outside, in a chair outside the dorm room. The door to the room was wide open. The student smiled and said he was enjoying the cool breeze coming through the doorway. I had to do some explaining to him about the purpose of air conditioning."

Saint Leo University receives electric service from TECO Energy Corp. Killmeyer noted that be-cause of frequent electric outages and the need for reliable service, the school put in its own diesel-powered electrical generating plant in conjunction with the central chiller plant.

The facility consists of two Caterpillar diesel engine-generator sets, rated at 1,000 and 600 kW. With these, the campus can carry its entire electric load, including air conditioning. In fact, the campus has been designated as an emergency hurricane shelter for area residents, including those with special needs for electric power to operate medical equipment.

For more information, visit www.trane.com.

Publication date: 09/20/2004