Advocate Good Samaritan Hospital, Surgery Addition

Downers Grove, IL

Air-handler and pipes, Advocate Good Samaritan Hospital, Downers Grove, IL.


GBA retro-commissioned HVAC systems serving a one-year-old, 75,000-square-foot hospital addition, which houses 16 operating rooms and support spaces.

The project resulted in verified energy savings of $100,685 annually, with a project payback period of less than one year.


The retro-commissioning effort focused on the temperature controls for the two surgery air-handling systems and the chilled water system serving these AHUs.

  • The air system includes two 50,000-cfm AHUs with steam integral face and bypass preheat coils, steam humidifiers, chilled water cooling coils, glycol cooling coils, and hot water reheat coils serving operating rooms with terminal units and reheat coils. Each AHU is sized to provide backup for the other AHU. Half of the ORs, which are served by one of the AHUs, have booster humidifiers at each room.
  • Chilled water is provided via either the main central plant or two local 250-ton air cooled chillers.
  • Functional performance tests were performed initially to identify problems, and were repeated to verify proper performance after corrective actions were implemented.
  • AHU issues that adversely affected energy consumption were identified. These included simultaneous humidification via the steam humidifiers and dehumidification via the cooling coil; outside air dampers 100% open when the design called for maintaining 25% outside air (thus requiring the preheat coil to provide heat at times when heat would not otherwise be required); and supply and return fan variable frequency drives locked into fixed speeds, thereby unable to modulate in response to varying airflow requirements.
  • Other operational problems found through RCx included improper fan safety settings, unreliable movement into and out of backup modes of operation, and equipment not shutting down properly.
  • Retro-commissioning benefits included improved temperature and humidity control, and a projected annual energy cost savings of approximately $100,000.

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