Famous Chicago Building puts pressure
on Green Initiative
When the world-renowned Merchandise Mart in Chicago began the task
of obtaining LEED-EB certification, it was just the fifth
building in Chicago to go “Green”. Adhering to standards set
forth by the LEED Green Building Rating System, a voluntary,
consensus-based national standard for developing
high-performance, sustainable buildings. The Merchandise Mart
focused on five key areas of green building strategy:
sustainable sites, water efficiency, energy efficiency,
materials/resources and indoor environmental quality as set
forth by LEED. Such on-going improvements involved reevaluation
of capital programs for replacement of windows, roofs, controls,
plumbing fixtures, utility meters and lighting.
To better target energy efficiency, just one of the many
strategies directed by Merchandise Mart’s Vice President of
Engineering Mark J Bettin, P.E. was replacing an outdated
domestic water supply system that was a large consumer of energy
and an inefficient supplier of water.
Original System
The original system consisted of five
pumps ranging in size from 40 hp to 75 hp. The pumps ran at a
constant speed intended for the highest demands even during
low-flow periods such as during the middle of the night. The
system was designed to deliver over 1250 gpm, churned at
290psig, and incorporated pressure reducing valves on the
discharge of each pump to maintain a system pressure at 200psig.
The five original pumps were oversized by 35HP each, totaling
175 unnecessary horses.
“With recent restroom renovations complete, the water consumption
and demand reduced annually by over 35%, resulting in an
oversized, inefficient pumping system.
It required large amounts of energy to run and replacing it would
help in the buildings’ on going energy reduction efforts and
contribute in maintaining the standards of LEED certification,”
Bettin said.
According to Merchandise Mart’s Plumbing Foreman, John Geiss, prior
to the retro-fit and during heavy usage the domestic water
system would see momentary swings in the system as much as
40-PSI at the top end of the system, resulting in noticeable
fluctuations at the fixtures and excessive pipe movement.
The Merchandise Mart is the world’s largest commercial
building, largest wholesale design center and one of Chicago’s
premier international business locations. Encompassing 4.2
million gross square feet, The Mart spans two city blocks and
stands 25 stories high. Today, The Merchandise Mart welcomes
more than three million visitors each year to its retail shops,
boutiques, 11 floors of permanent showrooms for gift,
residential, casual and contract furnishings, 10 floors of
office space, dozens of trade shows and a myriad of special
educational, community and consumer events.
During peak flows, which typically are during a large
tradeshow event or during the workweek, demand can reach 750
gallons a minute when up to 20,000 people populate the building
during major exhibitions. However, during low flows, as
witnessed during the early morning hours, demand can slow to a
few gallons a minute. With such a wide range of flows and given
the Merchandise Mart’s demanding show schedule where water
consumption constantly changes, the new domestic water system
would need to match not only extremely high flow demands but
also the low flow demands using the least amount of energy
necessary.
During the bidding process, quality, service and experience
were the criteria important to Bettin when choosing the
companies to complete the work.
“We pre-qualified the companies such as engineer KGWW,
Metropolitan Industries, Inc., Great Lakes Plumbing and Blaze
Electric based on their experience and reputation,” he said.
Chicago-based Great Lakes Plumbing was awarded the
design/build contract based on the proposal they submitted.
Great Lakes’ Bob DeGuiseppe, project manager, served as the
general plumbing contractor and pump and control system
manufacturer Metropolitan Industries, Inc. of Romeoville, Ill.,
designed the new system and pressure reducing zone stations
while Blaze Electric of Broadview, Ill. served as the installing
electrical contractor and KJWW of Chicago served as Engineer
during the project.
The New “Green” System
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Metropolitan’s design of the pump system and pressure
reducing zone stations was based on two specific goals
that included reducing energy costs on day one of
start-up; and ensuring enough redundancy to prevent loss
of service in the future due to power or mechanical
issues.
Working closely with DeGuiseppe, Metropolitan Chicago Sales Manger, Mike
Ponx suggested installing a variable-speed system that
would reduce energy costs by half due to the system’s
ability to precisely match demand using only the minimal
amount of energy necessary. |
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During low flow periods where little or no demand exists, a
variable speed system shuts down entirely saving energy and
money while four bladder tanks located in two separate locations
help maintain pressure, while the system is in shutdown / low
flow mode
The system supplied was a variable speed, quadraplex booster system
using vertical, multi-stage pumps, total system rated at 1000GPM
at 200 PSI. The Merchandise Mart’s peak flows are 750
gallons/minute so in a condition where any single pump fails,
the system will still be able to handle the load without shut
down. To add to the redundancy, there are two separate power
feeds divided between the system. Feed A runs three pumps and
Feed B runs two pumps. If either feed A or feed B is lost, the
building will still have one electrical feed to supply water to
the building without interruption or system shutdown. The
electrical control system and plumbing design was also
configured to one existing pump to operate as a manual stand-by
pump to further add redundancy to the building.
The building is divided into four zones to stabilize pressure. At
each zone, pressure reducing valves were downsized to
maintain each of the zone’s pressure requirements and the
four bladder tanks were installed on the 6’’ cold water express
risers to sustain pressure when the system shuts off during low
flow periods.
Using bladder tanks at the top of the express riser, pressure
is stored so the system can shut off during low flow
periods. As flow is consumed the pump system will activate and
supply water to the building at the desired pressure. Once the
demand for water is reduced to a low flow period, the system
will shut off once again. Significant energy savings is realized
during low flow periods when using variable speed drives and
bladder tanks in combination.
During installation of the pumps and controls, interruption of
service did not occur to the building said DeGuiseppe. “Since
the existing booster system had two independent electrical feeds
and the building could not be without water at any time, the
electrical controls were built into two sections, which would be
mated together during the second phase, he said. DeGuiseppe
spilt the new control panel into two sections, Blaze Electric
installed the main control section first after disconnecting the
first electrical feed, than installed the first two of four
pumps using the new controls. Once the first two new pumps were
online Blaze Electric removed the old panel and installed the
second half of the new control panel, which was designed to mate
up to the first section. After that, the remaining two pumps
were installed.
Green Savings
The energy savings realized using a
variable speed booster system are tremendous. In order to
commission the system and measure the savings, meters were
installed to measure flow and energy consumption.
Results appeared quickly with the installation of the first two
pumps. Energy reductions in the first week were 34%. With
completion of all the pumps, the bladder tanks came on line and
the system was set for commissioning. Utilizing a system
by-pass and real-time flow meter, various loads were created to
allow for fine tuning of the drives and staging of pumps. With
the removal of the top zone PRV, the system pressure was
successfully lowered from 200 to 185. Taking advantage of the
bladder tanks, the night-time mode was enabled resulting in the
cycling of pumps. Week after week evaluation has shown a
reduction in energy by up to 50% with an anticipated annual
energy reduction of over 125,000 kwh.
Within a decade, the system will pay for itself entirely on
energy-savings and the expected life of this system is over
25-30 years so eventually the system will not only pay the
end-user for the cost of the system but it will also pay the
costs to replace itself in its lifetime!
Conclusion
According to Geiss, the completion of the retro-fit work improved the
overall performance of the system by lowering working pressure
and reducing fluctuations throughout the system.
“For the first time we have experienced the most even flow and
the best overall PSI performance at the top of the 10th, 18th
and 25th floor zones,” he said.
This was accomplished by reducing the size of the valves in the
respective zones to “tighten,” up the flow in conjunction to the
smooth operation of the variable speed booster system and
bladder tanks that feed and assist the entire system as a whole.
“Overall Metropolitan and all parties involved came through with
the promise and commitment to a 2-4 psi swing, and an energy
savings that will match the Merchandise Mart's committed effort
to LEED providing for a GREENER tomorrow,” said Geiss.
