Fox Tower is a large 27-story class-A office building in downtown Portland. Built in 2000, the building achieved LEED Gold certification in 2012.
A unique design aspect was the large air handling unit (AHU) located in the mechanical penthouse that served all floors of the tower except levels one and two. The original AHU had large vane axial fans with 500 HP and 270,000 CFM of airflow that experienced vibration issues. Multiple catastrophic fan failures impacted building operations and damaged the penthouse. An aggressive vibration monitoring program was implemented by the owner that reduced fan airflow to control the vibration issue. Because of the system's high airflow and static pressure, there was no viable replacement option for the existing fans, until recently.
To tackle this system challenge, Säzän Group was selected to lead a CM/GC project using an integrated mechanical delivery approach. This strategy incorporated design, commissioning, energy analysis, and procurement support to understand the holistic system design, forecast constructability challenges and implementation risks, and optimize the design. In addition to design, our team developed and solicited the CM/GC RFP, led the contractor selection, vetted the fan array manufacturers with the client, and conducted a detailed energy study funded by the utility.
This integrated process implemented a modular fan array system. This system removed the vibration issue while increasing redundancy; allowed for a phased, modular installation; and eliminated the need for a crane. The new array resourcefully reduces sound levels and incorporates the airflow monitoring system. No-loss discharge dampers, coupled with the lower sound levels, allowed the removal of existing sound attenuators, ultimately reducing overall energy usage. This resulted in a significant energy incentive (10%+ of the project cost to the client) from the Energy Trust of Oregon.
The modular fan array installation was phased as the building operations could not go down. Each of the three major supply and return fans was taken offline individually and demolished, with a new fan array constructed in its place. This work occurred at night to minimize client impact, maximize efficient installation, and eliminate safety challenges. The finalized install was commissioned and turned over to the owner.