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Chilled Water Systems: 50 Years of the Engineers Newsletter

September 12, 2022


The first-of many Trane Engineers Newsletters on chilled-water systems was published in 1973 with a concentration on chilled and condenser system piping design. At that time, chilled-water systems had a constant-flow design. This began to change in the late 1970s as a new technology, the variable speed drive, was applied to chilled-water pumps. To educate the industry, “A Need for Variable Flow Chilled Water Systems” (1977), “Water Chiller (Control): Decoupler Variable Flow Systems” (1979), and “Chillers are Constant Flow Devices” (1980) were published. These articles provided background on primary-secondary (decoupled) systems which operated more efficiently and became common design practice for the next decade

In the mid-1990s, variable evaporator flow, termed Variable Primary Flow (VPF), began to gain momentum, resulting in publication of Engineers Newsletters in 1999 and 2002. Variable condenser water flow was added to the chilled-water system toolbelt and covered in “The Impact of VSDs on Chiller Plant Performance,” (2013), Condenser Water System Retrofit Opportunities (2016), and “Impacts of Chilled-Water System Design Decisions,” (2018).

During the past five decades, additional chilled-water system subjects included chilled water and ice storage systems, waterside economizers (free cooling), waterside heat recovery, series chillers, design asymmetry, condenser water system design, system optimization, and even learning from past mistakes (how we would know about these past mistakes is a mystery?!?).

Through the Engineers Newsletters of the last 50 years, Trane has kept the reader at the forefront of chilled-water system education, design and operational knowledge, advanced controls, intelligent systems, and troubleshooting experience. Goals in doing so included system reliability, efficiency, simplicity, longevity, and understandability, resulting in proper system operation, operator understanding of and ability to troubleshoot systems, comfortable and productive building occupants, and efficient, economical and low-emissions systems for building and district plant owners. As we embark on the next fifty years and consider options such as electrifying hydronic systems to provide heat, keeping these goals in mind provides benefits to the building occupants, operators, owners – as well as YOU!

Using chilled-water systems, collectively we:

  • make buildings sustainable and resilient to future changes,
  • reduce the world’s energy utilization intensity and environmental emissions,
  • ensure vaccines stay cold,
  • optimize dehumidification and ventilation for indoor air quality, and
  • reduce food spoilage.

THAT is a cool honor!

Kasey Boxleitner

About the author
Mick Schwedler, Applications Engineer

Mick has been involved in the development, training, and support of mechanical systems for Trane since 1982. With expertise in system optimization and control (in which he holds patents), chilled-water and geothermal system design, and decarbonization of hydronic systems. Mick’s primary responsibility is to help designers properly apply Trane products and systems. Mick provides project-specific support, writes technical publications, and presents seminars.

Mick is an ASHRAE Fellow and served as ASHRAE President 2021-22. He is a recipient of ASHRAE’s Exceptional Service, Distinguished Service and Standards Achievement Awards. He is past Chair of SSPC 90.1 and contributed to the ASHRAE GreenGuide. Mick has been active on several USGBC technical and education groups, chaired the LEED Technical Committee and served on the LEED Steering Committee. Mick earned his BSME degree from Northwestern University and his MSME from the University of Wisconsin Solar Energy Lab.