College of DuPage

Chiller Plant Replacement, Design

Chiller Plant Replacement, Design - Glen Ellyn, IL


The project upgraded the college's existing chiller plant, including the installation of new chillers and reconfiguration of one existing chiller. The total cooling capacity of the plant was increased to support campus expansion and renovation. The new chiller plant saves 4.67 million kWh per year compared to the old plant: a 50% cut in annual electricity consumption. The resulting reduction in CO2 emissions -- 5,577 tons of CO2 per year -- is the equivalent of removing 923 cars from the road.


Source Award
ASHRAE Illinois Chapter 2009 Excellence in Engineering Award


  • The new plant includes four new chillers: two at 730 tons, two at 1,500 tons, and one existing chiller with a capacity of 1,200 tons, for a total installed capacity of 5,660 tons.
  • The new chillers were pre-ordered by the college based on a life cycle cost analysis.
  • The chilled water distribution system was converted from primary/secondary variable flow to primary variable flow. Variable frequency drives were provided for all pumps (chilled water and condenser water), cooling towers, and two of the chillers.
  • The controls optimize the operation of the chillers, pumps, and cooling towers based on total plant load.
  • A detailed hydraulic analysis of the entire campus distribution system was performed, identifying the need for a secondary distribution pump for one of the buildings.
  • The make-up water requirement for the cooling towers was reduced by 2.32 million gallons per year: an 11.6% reduction.