condensing (85° F) or to provide 45°
F brine for free winter cooling via
the packaged HVAC units’ water-
side economizer coils.
All exterior cooling tower and
fluid cooler piping is heat-traced,
covered with glass fiber-rein-
forced insulation with vapor bar-
rier, and encased in aluminum
jacketing.
The cooling tower, fluid coolers,
two packaged HVAC units (for the
11th floor), three pumps, and pip-
ing had to be lifted to the roof by a
helicopter; 36 separate lifts were
required. The heaviest equip-
ment--tower and fluid coolers--
had to be broken down in sections
no heavier than 19,000 lb and
then reassembled on the roof.
Prior to lifting, all equipment was
unloaded and staged at a down-
town parking lot on a Saturday
and hoisted to the roof on a Sun-
day.
Space heating
All space heating is electric.
Early in the project, a study was
made to determine what fuel/en-
ergy source would be used for
space heating and cooling. While
electric heat is costlier than natu-
ral gas, the investment cost for
the all-electric system was suffi-
ciently lower to yield an attractive
owning and operating cost. Part of
the investment cost saving was
due to the fact that with an all-
electric building, the electric util-
ity company would supply the 12
KV electrical risers. Two such ris-
ers were provided--one for the
north half and one for the south
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half of the building.
Transmission heat loads are
controlled with linear perimeter
radiation. In many locations,
these heating units are located at
the window-sill level rather than
at the floor.
Both VAV and fan-powered ter-
minals are used to introduce sup-
ply air to the conditioned spaces.
The fan-powered boxes have elec-
tric coils and generally serve
perimeter spaces. Their controls
are interlocked with the perime-
ter radiation controls so the two
systems work efficiently together
rather than possibly wasting en-
ergy by fighting each other--i.e.,
the terminal "sees" a cooling load
while the nearby perimeter radia-
tion senses a heating load.
Central control system
DePaul Center is controlled by
a central DDC building automa-
tion system. The functions it con-
trols/supervises include HVAC,
fire protection, building security,
and lighting. The HVAC equip-
ment/functions covered include
the chillers, packaged HVAC
units, cooling tower, fluid coolers,
economizer cycles, optimal start-
stop, and status reports for each
half floor including data on fans
and VAV and fan-powered boxes.
The control operator work sta-
tion is in the DePaul facility
across the alley to the east. A five-
level bridge connects Floors 7 to
11 of DePaul Center with the
O’Malley Center.
Plumbing/fire protection
The new water service to the
building consists of two parallel
12-in. lines. A valve was installed
in the city water line between the
two pipes supplying the structure,
permitting the city line to be shut
down in either direction without
interrupting flow to DePaul Cen-
ter.
A packaged duplex pressure
booster system was installed to
provide adequate domestic water
pressure and flow to all floors.
This assembly has two 40-hp
pumps supplying 400 gpm at
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rated conditions.
A number of electric water
heaters were installed throughout
the building. These serve from
one to three floors. Recirculating
hot water systems were installed
to all washroom facilities. Two
cold water risers, each serving
half of a floor, supply their respec-
tive heaters and the cold water re-
quirements of the restrooms. Wet
columns were installed to provide
for tenant water needs.
New roof drains and internal
downspouts were installed as
were new basement sump pumps
and sewage ejectors. Appropriate
backflow devices were installed
where required.
All building levels are sprin-
klered and are fed by two 1500-gpm
fire pumps. One serves the low
zone and the other the high zone.
Electrical
The building has two 12 KV
feeds with automatic load trans-
fer between them. As previously
noted, the power company sup-
plied twin 12 KV risers in the
structure.
Lighting and power distribu-
tion throughout is all new. Distri-
bution voltage is three-phase, 480
v for power and 120/208 v for re-
ceptacles and lighting. Lighting is
primarily fluorescent in the ten-
ant, university, and service area
spaces. Cool white lamps predom-
inate, but classrooms generally
have warm white lamps. Incan-
descent lamps were widely used
on the main and concourse levels
to obtain the desired visual effect.
Conclusion
An extensive rehab of a large
building is expensive. It generally
is, however, much less costly to
reuse a sound structure than to
tear it down and build another
major structure on the site. To-
day, the once-old department
store is poised to enter the next
century as DePaul Center--an
important, modern addition to the
university, the commercial office
and retail communities, and the
City of Chicago.
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