Sam Nunn
ONE OF THE EAST COAST’S LARGEST BUILDINGS FINDS TRANE HAS BIG IDEAS
A TRANE HVAC SYSTEM MAKES THE SAM NUNN FEDERAL CENTER IN ATLANTA AS COMFORTABLE AS IT IS LARGE
The Sam Nunn Federal Center in Atlanta, GA is one of the largest buildings on the East Coast. It encompasses a mind-boggling 1.87 million sq. feet and, because of its many resident agencies and businesses, it is in operation 24 hours a day, 365 days a year. That much space, combined with the facility’s never-ending workload and Atlanta’s notoriously hot and humid weather, presented a large-sized HVAC challenge—a system this complex generates unique issues. Aside from providing comfort to its many residents and round-the-clock performance for critical facilities, special care had to be taken to ensure that noise from the sheer volume of HVAC didn’t affect building tenants. Large buildings have large challenges, and Trane has experience finding the answers.
Bill Faulkner, Sales Engineer for the Trane Atlanta commercial sales office worked extensively with the owners and Newcomb & Boyd, the contracting/construction team, to solve the facility’s HVAC challenges. They designed a system consisting of four Trane CenTraVac™ Model CVHF 1280 chillers rated at 1,310 tons plus one smaller Trane CenTraVac Model CVHE 500 machine rated at 400 tons. All of these direct-drive, R-123 chillers benefit from Trane’s EarthWise technology; they are highly efficient, working at low speeds and low pressure to save on both resources and utility costs. Many owners find they pay for themselves in as little as a few years just in cost savings alone. For even greater efficiency, the plant also features a plate and frame heat exchanger to allow economizer cooling without having to operate the chillers when outdoor weather permits (an average of 1,643 hours a year in Atlanta). Distribution of chilled air in the building is accomplished with 100 Trane Modular Climate Changer™ central-station air handlers and associated fan-powered VAV boxes. Faulkner noted an additional challenge associated with that many air handlers: “[The building’s owners] set a required sound performance level of NC 40 just outside the mechanical rooms and NC 35 elsewhere on the occupied floors. This was an interesting design challenge.”
The modularity of the Climate Changer Air Handlers was the key to solving this challenge. Because of the unique “building block” design of the Climate Control air handlers, they have nearly unlimited flexibility in the way the units’ fan, coil, filter and plenum modules are connected. This made it possible to configure the air handlers in a blow-thru double-deck stacked configuration. Turning the airflow within the air handler using dual-discharge plenums attenuates the low-frequency fan sound using a phenomenon called “end reflection.” The net is a reduction in the transmission of sound at the air-handling unit as well as radiated sound.
The air handlers also help insure IAQ with particle filtration down to the small micron sizes, and according to Faulkner, because of the stacked configuration, clean-up crews can vacuum and wash every square inch of the air handler interior, including coils. “It’s almost like a food service level of cleanliness,” he said. Now that the system is up and running, Faulkner says his measure of success is how few comfort complaints he receives, “Typically it’s eight to ten comfort-related trouble calls per month. For a facility this size and with this many occupants, that’s phenomenal.” No, that’s Trane.
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