Florida Campus Uses Dispersed Chiller Plant With Central Control
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
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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 modernarchitecture. 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 operateon 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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