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Wright Runstad - Auxiliary Cooling Loop Expansion

Result: Cooling capacity increase, energy savings and operational flexibility

1201 3rd Avenue Building, Seattle, WA is a 57-story office tower constructed in 1987. The building was constructed with a primary chilled water system and an auxiliary condenser water system. The auxiliary system is dedicated to retail, tenant comfort and data cooling.

Over time demand on the auxiliary cooling water loop exceeded the system’s heat rejection capacity. This project consisted of increasing the capacity of the auxiliary loop system by 30% due to increase in building cooling loads.

Construction was performed during mild weather season and employed redundant backup heat exchange system constructed in 2009 by our team to reject the auxiliary loop heat to the chilled water condenser water loop on Floor 35.These revisions were performed to provide system flexibility and allow for Auxiliary loop shutdown and maintenance during cool weather

Scope or Work

  • Replacing closed loop N+1 pumps located on Floor 33 with new larger pumps to maximize flow within feet per second limitations of existing piping.
  • Adding plates to the plate & frame heat exchangers located on Floors 33 & 56.
  • Replacing open & closed loop N+1 pumps located on Floor 55 with new larger pumps to maximize flow within limitations of existing piping.
  • Demo of existing and field erecting (2) cooling towers located on Floor 57 to effectively reject 30% additional heat from the auxiliary loop system. The selected cooling towers used less fan HP and reduced static pressure resulting in operational energy savings in addition to the capacity increase.
  • Cooling tower replacement was achieved by hand demolition of two existing tower and hand building two new cooling towers within constrained structural surroundings. The new cooling towers were shipped knocked down and rigged to the rooftop location. The System team hand assembled both tower systems using a custom designed 5 axis hand rigging assembly. All supply and return piping 10” and 8” were pre-fabricated, rigged and assembled on site.
  • Upgrading open and closed loop pumps to variable frequency drive control.
  • Implementing optimized sequence of operation.
  • Commissioning.

Complete refurbishment of two critical rooftop Cooling Towers with modifications to the piping systems to facilitate the transfer of building primary loop to auxiliary loop. Replacement was a costly option and shutdown of these towers was not possible. Expand capability of new auxiliary PHE system to utilize heat rejection capacity of CT-1 (one of four CHW Cooling Towers) during conditions of moderate load. Redundancy needed to be achieved in order to facilitate refurbishment and routine maintenance of the rooftop towers. The modifications designed and installed by our team facilitated the transfer of cooling load to the primary building loop. Rooftop tower refurbishment included complete fan, motors, fill, polyurea tank linings and modifications for increase tower lifespan and efficiency.

Modifications to piping systems to facilitate transfer of building primary cooling loop serving  floor 4  through 33  to auxiliary loop serving floor s 33 to 54..

  • Complete refurbishment of 2 rooftop  critical cooing towers
  • Including tank linings, heat exchanger installation and modifications , VFD applications, Rotating assemblies , motors, pumps and related piping modification to CHW risers during critical weekend  shutdown .
    • Expand capability of new auxiliary PHE system to utilize heat rejection capacity of CT-1 (one of four CHW Cooling Towers) during conditions of moderate load. Provide serviceability and redundancy for the auxiliary cooling loop by allowing transfer of rooftop tower load to primary loop during wider range of load conditions