CDA chose Burns & McDonnell for planning, design, engineering and construction services to support the replacement of five chillers; upgrades to four chillers, the South Cooling Tower and the chilled water booster pump systems; and the replacement of the chilled water system controls at O’Hare. This equipment was in the H&R Plant and the utility tunnels serving the main terminal mechanical rooms.
To increase capacity and improve the efficiency of the H&R Plant, the team evaluated multiple options. Variable speed chillers, a combination of variable and constant speed chillers, variable speed pumps, and a thermal energy storage (TES) tank to upgrade the chilled water system were all considered. A final design was selected that included variable speed chillers and a variable primary pumping system.
H&R Plant upgrades included replacing four existing 2,000-ton chillers with three 4,500-ton chillers for an increased capacity of 5,500 tons. Chiller upgrades also included the replacement of an existing 4,500-ton constant speed chiller with a new variable speed chiller, and new controls on four existing 4,500-ton chillers. The existing constant speed primary chilled water pumps were replaced with 10 new 1,000-horsepower variable speed chilled water pumps, and the central chilled water system controls for the entire H&R Plant were replaced.
The existing 8,000-ton South Cooling Tower was renovated and expanded to 13,500 tons, two 3,000-ton plate heat exchangers were added for free cooling duty, and cooling tower controls were replaced. Free cooling heat exchangers were piped in tandem and designed to satisfy the entire winter cooling demand when outdoor air was below 30°F. The system cools 54° water to 42° from the cooling towers, which have steam basin heaters to facilitate winter operation.
Terminal booster pump upgrades included replacing 40 chilled water booster pumps and upgrading all associated controls in 16 booster pump zones throughout the terminals.