Portland Building Installs Under-Floor System
The warehouse, located in Portland’s revitalized, post-industrial neighborhood known as the Pearl District, presented unique challenges in design. It also offered the opportunity to install a very different heating and cooling system provided by The Trane Company.
The primary comfort system for most of the office spaces in the building features six self-contained air conditioning units rated at 30 tons each. These Trane Signature Series™ units, Model SCWF, are located in space saving mechanical rooms placed throughout the building. Gerding/Edlen Development Company, a real estate consulting and development firm, spearheaded the renovation project. According to Dennis Wilde, senior project manager with Gerding/Edlen, “One reason we chose self-contained units was space considerations. Minimal floor space and service space is required around each unit.”
The self-contained units are water-cooled and are served by a cooling tower on the building roof. Other key elements in the design are outside economizers that interface with all of the self-contained units. Because of the moderate climate in Portland, up to 65% of the time, building cooling can be handled on the economizer cycle.
This raised flooring design also created a void to serve as an air distribution plenum. Conditioned air flows to occupied spaces through floor diffusers that can be adjusted to meet local needs and preferences. System operating pressures are typically about 0.1 in. H2O. Conditioned air is delivered at temperatures of around 65 degrees F. Because the entire sub-floor area serves as a distribution plenum, space conditioning is also accomplished with direct radiation through the floor panels.
Trane also says that to meet the need for building heat, perimeter zones on each floor are served by separate single-duct variable air volume (vav) systems supplied by the self-contained units. These zones are baffled off from the balance of the floor area. The vav units that serve these areas are equipped with hot water reheat coils.
The entire environment is also controlled with a Trane Tracer Summit™ building management system. Trane wireless zone sensor thermostats provide local zone comfort control. Like the floor diffusers, individual zone sensors can be relocated as the building floor plan is revised. This system then communicates with the self-contained units, economizers, perimeter heat, and zone sensors.
Finally, the owners also wanted to minimize the acoustic impact of the hvac system.
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“We achieved that by lining the mechanical room walls and through the low-pressure air distribution design,” said Wilde. “You can’t hear the air moving below the floors, but it’s there.”
Publication date: 05/20/2002
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