Half-Day Workshop

Variable Flow Chilled Water Plants: Operating Theory and Field Opportunities

  • David Sellers, PE – Facility Dynamics

This workshop explores variable flow chilled water plants using an interactive format that includes lecture and also uses Sketchup models, selected software, spreadsheets, and case studies to illustrate and explore:

  • Design concepts and assumptions behind variable flow primary-secondary plants
  • How advances in technology allowed the industry to move to variable flow primary only chilled water plants and variable flow condenser water systems
  • How the advances referenced above have introduced a number of potential operation and maintenance issues
  • How real world operating characteristics of cooling coils relative to the design condition can cause their performance to deviate from the design intent
  • How critical it is to understand the daily and seasonal load profile in terms of optimizing the design and operation of a variable flow plant
  • How knowledge of the real time load profile can be used to advantage to achieve best life cycle cost equipment selections
  • How knowledge of the real time operating profile and the kW per ton profile can be used to optimize chiller staging strategies and equipment upgrade decisions.
  • How common variable flow plant retrocommissioning opportunities can be identified, assessed, and developed to deliver resource savings and performance improvements.

While the class will generally use central chilled water plants and condenser water plants for the case studies and exercises, the concepts are transferable to variable flow heating hot water plants.

It should also be noted that many of the fundamental principles that will be discussed can be broadly applied to other types of building systems, for example:

  • Centrifugal machine operating theory and optimization strategies,
  • The system concept, and
  • The importance of the load profile.

After completing the class, attendees will:

  1. Be able to recognize and have a basic understanding of common variable flow plant designs and configurations.
  2. Be able to identify and understand how to assess common variable flow plant existing building commissioning opportunities.
  3. Have a basic understanding of low delta t syndrome, its symptoms, and possible design and field solutions that can be used to handle it.
  4. Recognize the importance of understanding the daily and seasonal load profile for design and operations work and be familiar with some field techniques that can be used to assess it in an existing building.
  5. Recognize the importance of applying the system concept to inform design and operating decisions.

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