TECHNICAL FEATURE thanks to the fan laws.† In addition to the significant energy savings, this control sequence has other benefits, including: * Significantly improved condenser water temperature control; * Fan system maintenance is minimized thanks to the lower average fan speed and reduced starts and stops; * The cooling tower has a lower sound profile due to the lower average fan speed coupled with the soft fan starts and stops; and * All fan motors are regularly exercised without the need for a lead/lag arrangement. This simple energy-saving technique can be effectively applied on both new and existing installations. Of course, both the minimum fan speed and flow requirements for the specific cooling tower design must be followed per the manufacturer's recommendations. Note that this fan control method for multi-cell cooling towers and other heat rejection equipment has been added as a requirement in Standard 90.1-2013 PHOTO 2 Multi-cell counterflow open circuit cooling tower installation. along with a 5% increase in the minimum efficiency for axial fan, open circuit cooling towers. Additionally, a limitation on the use of centrifugal fan, open circuit cooling towers over approximately 300 nominal tons (1318 kW) was incorporated in the 2010 edition of the Standard helping to accelerate an important market †Assumes full design water flow over each cell in both cases; exact percentage savings will vary depending on the specific wet bulb, load conditions, and the estimation of the natural draft cooling capacity of the two cells with the fans off. www.info.hotims.com/49801-44 36 ashraE JourNal ashrae.org FEBRUARY 2014