23
Operation and Maintenance Instructions
Ice Management
When operating an evaporative cooling unit in extreme ambient conditions, the formation of ice is inevitable. The key to successful
operation is to control or manage the amount of ice that builds up in the unit. If extreme icing occurs, it can lead to severe
operational difficulties as well as potentially damaging the unit. Following these guidelines will minimize the amount of ice that
forms in the unit leading to better operation during the cold weather season.
Induced Draft Units
When operating an induced draft unit during the cold weather season, the control sequence must have a method to manage
the formation of ice in the unit. The simplest method of managing the amount of ice buildup is by cycling the fan motors off.
During these periods of idle fan operation, the warm water that is absorbing the building load flows over the unit to help melt
the ice that has formed in the fill, basin or louver areas.
In more severe climates, the incorporation of a defrost cycle can be used to manage the formation of ice in the unit. During
the defrost cycle, the fans are reversed at half speed while the system pump flows water through the unitʼs water
distribution system. Operating the unit in reverse will melt any ice that has formed in the unit or on the air intake louvers.
Please note that the fans may need to be cycled off prior to a defrost cycle to allow the water temperature to rise. The
defrost cycle requires the use of two speed motors with reverse cycle starters or reversible variable frequency
drives. All motors supplied by EVAPCO are capable of reverse operation.
The defrost cycle should be incorporated into the normal control scheme of the cooling tower system. The control system
should allow for either a manual or automatic method of controlling frequency and length of time required to completely
defrost the ice from the unit. The frequency and length of the defrost cycle is dependent on the control methods and ambient
cold weather conditions. Some applications will build ice quicker than others which may require longer and more frequent
defrost periods. Frequent inspection of the unit will help “fine tune” the length and frequency of the defrost cycle.
Forced Draft Units
Defrost cycles are NOT recommended for forced draft units, since allowing the leaving water temperature set point to rise causes
the fans to be off for very long periods of time. This is not recommended for forced draft towers because of the potential for freezing
the fan drive components. Therefore, the defrost cycle is an inappropriate method of ice management for forced draft units.
However, low speed fan operation or variable frequency drives maintain a positive pressure in the unit which helps prevent ice
formation on the fan drive components.
For more information on cold weather operation, please request a copy of EVAPCOʼs Engineering Bulletin 23
Replacement Parts
EVAPCO has replacement parts available for immediate shipment. Most orders ship within 24 hours from time of order!
To order replacement parts, please contact your local EVAPCO representative or Mr. GoodTower Service Center. The EVAPCO
representative with contact information is located on the unitʼs nameplate or can be found by visiting either www.evapco.com or
www.mrgoodtower.com.
The local EVAPCO representative or Mr. GoodTower Service Center can provide FREE unit inspections to help ensure your
equipment operates at peak performance regardless of the original manufacturer!
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