During winter operation, a cooling tower brings as much low temperature air into contact with the flowing water as the tower fan(s) will permit. The greater the flow of cold air, the colder the water temperature will become. Fortunately, when under design process heat loads, the temperature gradients that naturally occur in counterflow cooling towers (all Delta designs) prevent the mass flow of water from reaching 32°F. 

Cooling tower water will freeze very reluctantly and usually with advance warning. Here are some basic operating rules that should be followed for cooling tower operation in cold weather: 

  • Ensure that the cooling tower is operating at the maximum possible heat load. An operating cooling tower will continuously extract heat from the circulating water. Without a heat load, the water will end up either at the air wet bulb temperature or as ice, whichever comes first. 
  • Maintain designed water flow rate over the fill. Reducing water flow over the fill area can produce semi-dry regions that are subject to rapid freezing. 
  • Make sure a thermostat is installed to control fan operation to off at lower cold water temperatures.
  • If the tower is equipped with a VFD or two speed motors, operate at a reduced or low speed to increase water temperature leaving the cooling tower.
  • Check cycle fans periodically to prevent ice from forming on louvers.
  • Frequent visual inspection and routine maintenance during sub-freezing operation is very important.
  • If ice buildup occurs, use caution when removing the ice to prevent tower damage or injury to the employee. 

You can read the blog from Delta Cooling Towers here.