How to Prepare for Seasonal Chiller Shutdown and Lay-Up
Author: Andrew Young - Business Development Manager
The leaves on the trees are beginning to change colour and temperatures are fluctuating day to day. We have officially entered the cooling shoulder season. Temperatures this time of year result in a period of intermittent system operation followed by winter shutdown. While control of water chemistry is vital to minimizing HVAC system corrosion and preventing deposit formation during the cooling season, additional factors begin to play a critical role during the shoulder season and winter months.
Shoulder Season Cycling
End of Season Disinfection and Cleaning
Dry or Wet Lay-Up?
Since the system will be flooded with water, it is necessary to add a corrosion inhibitor to minimize the corrosion rates of steel and copper. A molybdate based closed loop treatment, such as Klenzoid’s Molyklenz, contains inhibitors for both ferrous metals and non-ferrous materials (copper/brass.) A target of at least 100 ppm sodium molybdate should be achieved in bulk water.
When the chiller is layed up wet, it provides the ideal habitat for bacteria. Since the regular biocide program will be offline for the season, it is necessary to add biocide directly to the chiller. Typically non-oxidizing biocides, such as Klenzoid’s Klencide GA15 or Isoklenz KT, are added per the vendor’s instructions to minimize biological activity.
Once the system is treated with corrosion inhibitor and biocide, provisions should be made to circulate the water within the chiller. This can be done with a small recirculation pump connected between the drain lines on each end of the chiller. The pump can either run continuously or at least 1 hour every 6 hours to prevent deposition and corrosion conditions associated with stagnant water . A pot feeder and filter can be added to the recirculation loop to allow for the addition of lay up treatment and to remove any particulate from the system.
WANT TO LEARN MORE?
 P. Sisk et al., “Guidelines for Treatment of Systems Containing Enhanced and Super-Enhanced Tubes”, The Association of Water Technologies, www.awt.org/resources/technical_papers.cfm
 “Operation and Maintenance Instructions: For Evapco Induced Draft and Forced Draft Cooling Towers”, Bulletin 113E, Evapco, 2014.
 “Operations and Maintenance: Centrifugal Liquid Chillers”, Form 160.75-O1 (211), York by Johnson Controls.
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Andrew Young is a Professional Engineer and has a degree in Mechanical Engineering from the University of Waterloo. He is a Business Development Manager with over 10 years of experience designing and implementing solutions for water systems. In addition to being a water treatment expert, Andrew is also an expert in “backyard” food production - producing his own tomato sauce, sausage, and maple syrup.
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