When the task is installing 12-ton chillers on top of a 15-story building in a busy downtown location, creative thinking and meticulous planning are a must.

Murphy & Miller, Inc. (M&M, Chicago), recently passed this logistical stress test by employing new computer-aided design and drafting (CADD) technology in a retrofit for Carson Pirie Scott & Co's department store in downtown Chicago.

Dress Rehearsal

Carson's 46-year-old hvac system was in need of major renovation. The owners selected M&M, given the firm's focus on handling new hvacr problems in existing structures.

M&M proceeded to design a solution that salvaged as much of the existing system as possible, powered by a condenser and three new chillers - enough to generate 3,000 tons of cold air to cool almost 1 million sq ft for shoppers. The project called for installing the 850-ton-capacity York (York, PA) chillers on the roof of the 70-year-old, 15-story building.

Compounding the usual installation problems was Carson's location on the high-traffic corner of Wabash and Monroe, right in the heart of downtown.

"Due to the cost and size of the chillers, as well as the busy downtown location, the way we placed these units onto the building was critical," states Richard F. Vitiritti, M&M's vice president of engineering and installation services. "Any mistakes during installation could be both dangerous and costly."

The firm was already using CADD (Da-taCAD(r) from DataCAD LLC, Avon, CT) to design the details of the new system.

"Because CADD is such a powerful visualization tool, we decided to use it to stage a virtual dress rehearsal of the installation to ensure that everything would go smoothly," said Vitiritti. "We used CADD to place the chillers, checked for clearances, and determined the best approach for the crane operator prior to committing resources to the actual installation."

There were a number of potential obstacles near Carson's roof, including an elevated train track. Joel Macias, a project engineer for M&M, modeled the hvac components and surrounding structures using DataCAD.

"This was a great help to the crane operator," says Macias. "We created the aerial flight path of the helicopter and plotted out the crane height and angularities to help him see exactly how the chillers should be brought up to the roof."

Macias joined the firm only two weeks before the CADD dress rehearsal was to take place. At his previous job, he had used a different CADD system, working primarily in 2-D. Despite the learning curve, Macias says he was modeling with DataCAD "within days."

"DataCAD is great because you can draw in 2-D [plan view] and be creating a 3-D model at the same time," he explains. "And it has functions for designing elements I work with everyday: drawing buildings, floor layouts, and yes, even 16-ton chillers."

M&M also used CADD to model the inside of the mechanical room as well as all of the pipe work; then Macias created a plan layout of the entire operation.

"The plan layout was critical to the operation, and it had to be as detailed as possible," he says. "Once we had the plan layout ready, it gave us a game plan on what we had to do, especially so near the CTA [Chicago Transit Authority] tracks."

The next step was to take the plan view and organize a run-through with the crane operators. Every movement was planned precisely, and everyone understood where all the good and bad angles lay.

A Perfect Landing

With the plan in place and the layout completely mapped, the placement crew was ready to go to work.

Working on weekends whenever possible to avoid weekday traffic, the crew hauled the chillers to the roof. The movement and clearances were so tight, the crane had to block the CTA tracks repeatedly.

Yet, because of planning and communication with the transit authority, there were no delays, and the ballet of train and crane went flawlessly amidst a host of obstacles.

"The entire operation proceeded fabulously," Macias recalls. "The building owner was very impressed."ES