TMG constructed structural support for the placement of two air-cooled chillers on the roof of a historic office building in Washington, DC. The job was completed in collaboration with the client’s in-house technicians and provides cooling for the building’s production floor via the air-handling units. While the client was responsible for furnishing and installing some of the equipment and piping risers within the building’s interior, TMG’s responsibilities included architectural installations, all control wiring for the mechanical equipment and the purchase and installation of all electrical equipment installed on the roof, including wiring and conduit to the electrical panels/distribution boards.
Working on the roof of the three-story building, TMG demolished a structural steel roof top monitor, modified existing roof trusses dating back to the 1930s, installed “in-fill” structural steel roof framing, and then added a new metal roof deck to support the new equipment platform and the heavy load of the mechanical equipment.
The equipment platform itself (aka “dunnage”) is a structural, galvanized steel frame constructed to support the four air-cooled water chillers, a combined chilled water pumping package for air conditioning, and a dry cooler for process cooling. With an outside dimension of 24’ x 56’, the platform is suspended above the new roof membrane on 12 new columns supported by the modified roof trusses below. All crane work was performed “in the blind” several levels above the ground. Both welded connections and bolted connections have been utilized.