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At Emory University Tri-Stack
roof exhaust systems reduce costs and maintenance at
new 145,000 sq. ft. laboratory building addition
When Emory University in Atlanta,
one of the South's leading neurological research institutions
built a new 145,000 sq. ft. addition to its existing
350,000 sq. ft. Iaboratory building, university management
sought a high efficiency exhaust system for the new
facility's 75 laboratory workstations. Conventional
centrifugal fans were in place on the existing laboratory
building (Phase I), and people at Emory were considering
an additional centrifugal fan system on a common plenum.
When they looked at alternative approaches,
however, they learned of Strobic Air Tri-Stack laboratory
fume hood exhaust fans through Jon Crane, AIA, at Lord,
Aeck & Sargent, Inc., an Atlanta architectural firm.
Crane explored the possibility of installing Strobic
Tri-Stack fans with Emory during the construction document
phase; he had recently used Tri-Stack fans on another
project there and was satisfied with the results. The
new laboratory building required exhausting about 130,000
CFM through four Tri-Stack fans on a common plenum.
Among
the advantages Tri-Stack offered to Emory were elimination
of guy wires, mounting hardware, and architectural attachments
to the roof. The Tri-Stack system exhibits a lower roof
profile as well, and requires less roof space; maintenance
is also virtually eliminated.
"Costs
were a primary consideration," according to Crane.
"When you start considering the ducts, stack extensions,
guy wires, as well as the fact that we were going to
manifold the fans together, the Tri-Stack fans began
to make sense," Crane added. He also said that
because Strobic guarantees the system performance to
the inlet of the plenum, he expected the system to perform
to the required CFM that he was designing for.
After
a detailed analysis comparing both initial costs as
well as long term costs for Tri-Stack vs. a conventional
centrifugal installation with comparable performance,
the Strobic Tri-Stack fans were shown to cost less to
purchase, less to install, and less to operate over
a long term period.
For
example, one consideration was the reduction in electrical
power requirements. Due to the efficiency of the Tri-Stack
system, 27% HP consumption was saved over the centrifugal
alternative. In addition, since the Tri-Stacks possess
non-stall characteristics, the fans could operate with
variable speed drives, making the entire system pressure
independent to the variable volume system, thus further
reducing annual power consumption .
Considerations
which influenced the Emory University buying decision
Jon
Crane at Lord, Aeck & Sargent had successful experience
with Tri-Stack fans. On the other hand, his concern
that the people at Emory were cautious about new technology
was valid, since Tri-Stack systems are radically different
from conventional centrifugal fans. "To me, it's
the first quantum leap, I guess you can call it, in
the state of the art of laboratory exhaust system design
in 20 years," he said. Crane also said that the
Tri-Stack fan...is a much better fan "design-wise
and performance-wise, installation-wise, and maintenance-wise;
all the categories used to compare them against centrifugal
fans."
To
enhance efficiency, the Tri-Stack fan system at Emory
offers a high degree of redundancy which also helps
lower costs. "Emory's people wanted the fans on
variable speed drives; we specified the fans so that
if one was lost during operation, the other three would
be speeded up to compensate to provide the designed
CFM," Crane added.
Installation
of the Tri-Stack system was also substantially faster,
according to Crane another key advantage. He said that
installation speed, along with associated lower costs
for mounting hardware, plus simplicity of design also
played a role in the Emory buying decision.
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