Cooling Towers

Cooling towers are essentially a large metal box that circulates a fluid (typically a chemically treated water solution) in a water fall effect while a fan section blows ambient air over the falling water to reject heat. The cooled water is then pumped back to a chiller in a mechanical room for another pass through the system. The "waterfall" effect cannot cool the solution below ambient air temperatures that can range in the summer from 70 F. to 100 F. The air forced over the waterfall effect will result in evaporation of some of the solution and chemicals. Damages would occur if the system lost sufficient solution to starve the pumps or chiller. To prevent this from happening there is a float valve in the base of the tower (reservoir) that will sense the drop in water level and let city water enter the tank to the normal fill level. The heated water coming to the cooling tower from a chiller is as a result of the chiller rejecting heat from the water based system that is feeding fan coil units in condos and apartments or machinery in process manufacturing. Chillers in new condominium construction are almost a thing of the past as they have been replaced by heat pumps in each individual suite. This will save the condo corporation thousands of dollars per year in maintenance and energy costs, and provides the condo owner with total control over their comfort conditions. Any building being air conditioned with a chiller would be without cooling if the tower or the chiller broke down. The down time of the system could be lengthly and very costly. The cooling tower would not be used in the winter months when there is a risk of freezing unless they are required for process cooling. The tower would then be equipped with a heater in the reservoir to prevent freezing and the water mix could / would have a concentration of glycol antifreeze. Cooling towers that are not required during the winter months are valved off and drained. Spray nozzles for the water fall and filter screens are all removed, cleaned and stored for the next cooling season. The drain valve for the tower is left open to allow rain water and snow to drain while the system is not in use. When the cooling tower and chiller is turned off for the season the boilers in the mechanical room are turned on to maintain a suitable temperature in the piping system. Buildings that have individual heat pumps in the suites and no chiller will use the same piping system that the cooling tower was connected to, to circulate water from the boiler system at a temperature of approx. 55 to 85 F. Maintenance on cooling towers is essential as a breakdown could leave an entire building without air conditioning. Anything from a broken fan belt to bearing failure, pump failure or fan motor failure can shut down the system. This maintenance would be performed by your HVAC contractor on a monthly basis and is would be wise to have the superintendent of the condo building do a "walk by" everyday that the tower is in operation. A water treatment company should be contracted to maintain the chemical levels in the system. They will test and add chemicals to control algae formation, scale buildup and cleaners to prevent such things as Legionella bacteria.

It is becoming very popular to add motor speed controls to the large horsepower rated motors of cooling towers to save electrical energy. These are referred to as VFD's (variable frequency drives) or VSD's (variable speed drives). The speed of the large motors are regulated based upon the temperature of the water in the tower and this saves a ton of money during the course of the summer.

Your building automation company can look after monitoring the conditions of the cooling tower and also alarm the system should there be a problem requiring service.

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