South / Regional Reports

Florida Campus Uses Dispersed Chiller Plant With Central Control

November 5, 2001
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By any measure, the University of Florida in Gainesville is large. Its enrollment of 46,000 is one of the 10 largest on a single campus in the country. Its faculty of over 4,000 is one of the largest in the southeastern U.S. and its campus, encompassing 2,000 acres and over 200 academic buildings in the city of Gainesville, is enormous. It is this scale that makes the university's approach to comfort-cooling interesting and instructive.

COOLING NEEDED YEAR-ROUND

Because of the campus' location in central Florida, building cooling is essential. Nearly all of the cooling in the major academic buildings, laboratories, and health care facilities is by chilled water. In scale with other campus features, the chilled-water system on the campus is also very large.

An interesting feature of the campus cooling system philosophy is the decision to rely on area chilled-water plants throughout the campus, rather than either a single central plant, or individual units for buildings. The area plants — currently eight in number — deliver chilled water, typically from centrifugal chillers, to surrounding buildings. Most serve buildings within a 1,000- to 1,500-ft radius. In the area of greatest building density, several chiller-plants supply a common chilled water loop. In other cases, plants with multiple chillers serve a specific group of buildings. In total, the eight chiller-plants provide the capacity for 37,000 tons of chilled water.

GROWING WEB OF PLANT CAPACITY

According to the physical plant's chiller plant supervisor, Charlie Milford,

the decision to use area chiller plants was partly a result of the

development of the campus' high-building-density areas, and partly the

recognition that chilled water pumping cost from a single chiller plant would

be exorbitant. The rapid development of the campus in the past 10 years has

meant that at least one chiller a year is required to meet year-round

building cooling needs.

Another interesting aspect of the campus chilled-water system is that all

plants are on a central management system — a Tracer Summit™

system by Trane. Detailed status reports on all of the chiller plants can be

viewed from stations at each plant, as well as at the Heat Plant II location,

staffed 24 hours per day.

Milford indicated it has become a habit for all plant operators to check the

status of their assigned plants regularly, as well as to compare them with

other plants on the campus. Milford said, "If performance of one of the

plants is declining, we pick it up right away. It might be tube-fouling or

tower-water conditions, but we can spot it because the plants are basically

designed to operate to a common standard."

In almost all cases, the chiller plants are designed and operated to deliver

44?F (7?C) chilled-water, with return temperatures at 54?F (12?C). Each plant

has its own cooling tower capability adjacent to the building. Towers are

designed for 85?F to 75?F (29?C to 24?C) operation. Most of the towers use

condenser water flows of 3.0 gallons (11 liters) per ton of operating chiller-

load.

PLANTS BLEND WITH CAMPUS ENVIRONMENT

The University of Florida campus has a blend of traditional and modern

architecture. Ivy-covered halls blend with live oaks draped with Spanish

moss. The chiller plants are largely freestanding buildings with design

elements to help them blend in with their academic neighbors. Cooling towers

are typically either screened with architectural and landscape elements or

located in low visibility areas.

The need for large capacity and high reliability has been combined with an

interest in holding down system operating costs. The university, in almost

all cases, has chosen to install electric centrifugal chillers. Because much

of the plant growth has been in the past 10 years, many of the chillers are

newer, high-efficiency models. In the interest of unit redundancy for

year-round operation, most of the plants have multiple units.

The predominant chiller type is the Trane multistage CenTraVac™ chiller,

Models CVHE and CVHF. In many of the plants, extra bays were included for

future machine additions. Likewise, piping and towers were designed to allow

for expansion. Plants range in size from 11,800 tons in Heating Plant 2 to

1,300 tons in the new West Chiller-Plant. Unit additions are already being

discussed for the latter plant, located in an expanding part of the campus.

LOOPED PLANTS ALLOW SELECTIVE DISPATCH

The Weil, McCarty and Walker chiller plants in the northeast campus operate

on a normally closed chilled-water loop. The three plants include 12 chillers

ranging in size from 450 to 1,425 tons, predominately Trane centrifugal

units. Their combined capacity is 14,000 tons. The Tracer Summit™ system

allows the physical plant staff to dispatch these units as needed based on

system efficiency. The chilled-water lines for the three plants meet in a

tunnel location beneath a main campus roadway.

Milford noted that, with looped operation of these plants, the physical plant

staff has the opportunity to take individual units out of service for tube-

cleaning or other routine maintenance without any loss of building comfort.

The same redundancy applies to cooling tower cells. Milford indicated "The

looped configuration also allows the most efficient units to be dispatched

first, and lets us keep units operating at their optimum load levels."

As the university's facilities expand, chiller capacity can be infilled at

existing plants, or new plants can be added. System efficiency increases with

newer chillers and advanced controls. Reliability comes from multiple units,

from interconnection, and from preventive maintenance. Most of all, what

appears clear on this campus is that the chilled-water system is as much a

part of the plans as dorms, libraries, and classrooms.

Publication date: 11/05/01

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