5000 Quorum

Project Summary

Turnkey EarthWise™ modification of chilled water system for increased cooling capacity, better efficiency and significant energy savings.

Challenge

Built in 1983, 5000 Quorum was originally fitted with two gear-drive centrifugal chillers in a parallel configuration producing 540 tons of cooling at 44°F chilled water temperature. In recent years building cooling load increased significantly, causing tenant comfort complaints. During summer months the chillers had to run all night because they could no longer pull down the temperature in the morning from the unoccupied set point. Chiller maintenance costs were also escalating.

Solution

The owner asked Trane and a competitor to provide bids for new, larger centrifugal chillers totaling 610 tons at 42°F. However, the increased cooling capacity would require a cooling tower gearbox change, adding $75,000 to the project cost. The engineers at Trane in Dallas applied Trane EarthWise™ design strategies to develop an effective, money-saving solution. Trane evaluated several options for increasing cooling tower capacity by 70 tons without any gearbox changes. Trane recommended increasing cooling tower heat transfer from 10°F to 13°F by reconfiguring the chiller plant to produce 40°F chilled water and slowing condenser water flow rate to 2.2 gpm per ton instead of 3 gpm per ton. Trane recommended installing the new chillers in a series counterflow system to reduce costs, improve efficiency and produce even lower chilled water temperature letting the chiller plant shut down at night without morning pull-down delays. A Trane Tracer Summit™ chiller plant control system optimizes chiller and cooling tower operation.

Results

5000 Quorum now has sufficient cooling capacity without the need to run the system overnight. 5000 Quorum is also realizing significant energy savings due to the new, efficient chillers and reduced pumping energy needed to move 40°F chilled water (instead of 44°F) at a slower flow rate while meeting ASHRAE 90.1 requirements. Maintenance cost savings are also significant. 

Fred Stillwell, Vice President and Director of Engineering for Transwestern and the building owner, said, "The system is working perfectly. The on-site engineer loves it. We have lowered our consumption and kW demand considerably. We saved 198,238 kWh from May to December 2009, versus May to December 2008 -- close to $20,000." 

Stillwell adds, "We are also able to run with only one chiller until outside air temperature reaches approximately 95°F. This was impossible with the chillers and parallel system we had in place previously. The Trane solution exceeded even my expectations. The tenants are far more comfortable now. Air conditioning hot calls dropped significantly after we brought the Trane chillers on line."

About 5000 Quorum

5000 Quorum is a unique, seven-story multi-tenant office building with 165,434 rentable square feet near the Dallas North Tollway. 5000 Quorum offers an on-site management office, deli and security. The building is just minutes from the Addison Airport and a block south of the Beltline Road restaurant and shopping area. It offers excellent accessibility to major thoroughfares as well as the Dallas-Ft. Worth International and Love Field Airports.

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