This paper responds to a letter in ASHRAE Journal in which a reader (Boghosian 2010) questioned how to control cooling tower fans and referred to pages 41.12 through 41.16 of ASHRAE Handbook-HVAC Applications (ASHRAE2007), questioning how to implement the Handbook's approach. The ASHRAE author (Dieckmann 2010) suggests the reader run a "comprehensive model" (Schwedler 2009) to answer his question. This paper answers the question posed by the reader with a plant simulation math model of the four chiller/tower plant of Example 1 on page 41.16 of the ASHRAE Handbook—HVAC Applications (ASHRAE2007), showing that a 24 kWfan tower without fan control can be more efficient than a 40 kWfan tower with fan control. This paper also briefly discusses using a simulation model to fine-tune plant operation and also shows that poor operation of a plant can result in significantly more energy waste than poor tower fan control. The paper ends with the suggested question: does simulation modeling have value in the quest for more efficiently designed and operated HVAC systems, and if it does, how does one pursue incorporating simulation modeling into the HVAC community?
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