Tower Inspections, Evaporation & Fan Speed

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• The following are questions and answers submitted to the “Ask the Expert” column at the Cooling Water Institute's CTI Journal — used by permission here:

Q: How often do we need to inspect cooling towers and what do we use as a code reference?

A: CTI has recommendations associated with maintenance of cooling towers. Please see our website for referenced standards. The institute has specific recommendations for control of Legionella, so please download the “Legionella Paper” for more details.

Q: I need a paper that compares water evaporation levels based on the fan speed. It must focus on how a user can reduce the water cost of Mechanical Draft Cooling Towers by use of motors with frequency changer or adjustable speed drivers.

A: A quick calculation can be made by assuming that the factor is equal to 0.1% or .001. This assumes the correct Liquid to Air Ratio so air leaving the cooling tower has reached saturation and has risen to approximate the inlet water temperature. The change in air flow will reduce the amount of air so the amount of heat removed will be directly proportional to air flow. The evaporation factor will drop proportionally. A 50% reduction in air flow will reduce evaporation by a factor of 50%.

Q: Do you have any guidelines or practical applications for smoke/fire detection in wooden cooling towers?

A: There have been two technical papers on fire protection that have been given at CTI that you may want to purchase, specifically TP62-07 “Fire Protection of Water Cooling Towers” and TP71-03 “Fire Protection and Cooling Towers” which are available at

Q: Why is ammonia not used in residential applications as a refrigerant, but so prevalent in industrial applications?

A: Ammonia is a very toxic gas. It's not used in residential applications because of potential for leakage into homes. Industrial complexes use ammonia refrigeration but under very stringent monitoring requirements. In reality, the typical homeowner would be at great risk from gaseous ammonia vs. standard refrigerant. The liability to the HVAC industry would be huge.

Cooling FAQs are provided by the Houston-based Cooling Technology Institute (CTI), a non-profit organization dedicated to improvement in technology, design, performance and maintenance of cooling towers and evaporative heat transfer systems (EHTS). They're from the “Ask the Expert” column of CTI Journal. Contact: 281-583-4087 or

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