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Optimizing Chiller Water Systems

An article written by Catherine Luthin expressing the importance of hospitals using a more sustainable approach. She reviews how old practices are being re-engineered to promote sustainability and boost efficiency.

Articles August 1, 2009

Greening Hospitals in New York City through Cost – and Energy – Saving Solutions

By Catherine Luthin

With healthcare being one of the few industries seeing growth in the United States today, hospitals are becoming increasingly aware of the importance of using a sustainable approach to that growth.

Many health centers are incorporating daylight into the wellness process. And to reduce energy consumption, many are scrutinizing the traditional ways of running hospital electrical and mechanical systems. Old practices are being re-engineered to promote sustainability and boost efficiency.

One challenge hospitals face relates to the build-up of unnecessary and inefficient pumping of energy through chilled water systems. Historically, consulting engineers have designed chilled water systems with major additional pumping loads. As the chilled water system became dynamic at certain load conditions, some critical areas of buildings did not get adequate chilled water. When chilled water distribution systems began to lose operating capacity, operators often installed additional pumps in a secondary system or implemented booster pumping.

Unfortunately, additional pumping results in a reduced system temperature between outlet and inlet water temperatures, called Delta T, and reduces chiller operating capacity. This, in turn, requires more chillers and auxiliaries for the given load and results in system inefficiency. Typically, the problem is not a lack of pump power but, rather, an incompatibility between different systems.

Solutions for New York City Hospitals

Identifying and re mediating these conditions has been a long-standing goal for Hemant Mehta, principal of WM Group (WM0, a New York City-based engineering firm. WM recently worked in partnership with the New York State Energy Research and Development Authority (NYSERDA) to conduct a forensic review of two world class New York City hospitals – and they identified a cost-saving and energy-saving solution.

The two nationally known facilities involved have several common characteristics: They both have multiple chiller plants with primary, secondary and booster pumping; the multiple plants are in different buildings in an urban campus; and the different buildings can share chilled water.

Hospital management recognized the loss in capacity and contacted WM and NYSERDA about New York State’s FlexTech Program, which offers cost-sharing incentives for energy-efficiency studies . The FlexTech Program has a list of contracted engineering firms, such as WM, enabling it to conduct studies confounded on an equal basis by the customer and NYSERDA.

WM began an optimization of the plants with the following goals:

  • Survey existing chiller plants and system designs to determine load requirements
  • Create a hydraulic model of the systems
  • Evaluate pump head requirements
  • Determine the compatibility of system components
  • Evaluate the system controls
  • Recommend system modifications

By maintaining a focus on sustainability through energy efficiency, the organization studies uncovered potential benefits that were too good to pass up.

Between the two facilities, WM found potential reduction in pump load of 2,900 horsepower, which would deliver annual energy savings of $1.1 million.

NYSERDA has funded both the energy study and implementation measures for the two projects with energy-efficiency incentives totaling approximately $1.2 million. For both hospitals, simple payback occurred within less than a year.

In the course of the optimization study, WM used innovative techniques and state of the art solutions:

  • A single, variable-volume, primary pumping solution was identified, which would ensure compatibility between systems.
  • A consistent application of chilled water supply and return temperatures was applied across the entire system; previously, each plant had different Delta Ts.
  • Large air handlers were checked for the controls of cooling coils.
  • All pumps were required to work together hydraulically.
  • All pumps had to be controlled from a common, differentiated pressure sensor in the main distribution line.
  • Multiple differential pressure sensors were installed on the main distribution system to determine ideal control settings. Optimum set-point for the pumps was determined through empirical data.

By implementing the WM optimization study, and with funding assistance from NYSERDA, two major New York hospitals are now realizing significant energy and overhead cost savings.

To carry forward its efforts to promote sustainability in New York State’s healthcare sector, NYSERDA recently announced a “Focus on Healthcare” initiative that is assisting hospitals and medical facilities statewide with implementing cost-effective energy efficiency strategies that reduce energy consumption and improve our environment.


Catherine Luthin is president and founder of Luthin Associates. Luthin has more than 25 years of financial and energy-management experience within corporate, nonprofit and regulatory environments. Based in Avon-by-the-Sea, NJ, Luthin Associates provides a wide array of energy consulting services to all industry sectors in the New York City region. Luthin Associates serves as implementation contractor for Focus on Healthcare, the NYSERDA initiative that assists the state’s healthcare industry with reducing energy and improving the environment while enhancing the treatment of patients.

For additional information, contact Natale DiDonato, CRM, project manager, under contract to NYSERDA Focus on Healthcare, at healthcare@nyserda or visit