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Revised 1-8-2007
14
Cold Weather Operation
Cold Weather Protection
The cooling tower may require protection against freezing at light heat loads when the wet-bulb
temperature is under 32°F., or during shutdown when the temperature drops below 32°F.
The following methods are recommended for use in Delta Cooling towers for protection during
cold weather conditions. Recommended equipment is optional and may be ordered from the
factory. Consult the factory for further information on which equipment to choose for your
specific application.
Separate Indoor Sump
This method is virtually a foolproof antifreeze protection system with the added advantage of
minimum maintenance. The indoor sump tank should be large enough to fill the entire
recirculation system without danger of pump cavitation. As a general rule, the tank should be
sized to hold three times the rate of circulation in gallons per minute (gpm).
The tank should be provided with properly sized overflow, make-up drain and suction
connections. When a separate sump is ordered with a cooling tower, the water make-up valve
assembly and the overflow and drain connections are installed in the indoor sump only.
When a sump tank is used, the cooling tower should be located high enough above it to allow
free cold water gravity drain. A bottom outlet can be provided for gravity drain to indoor sump
tank installations.
Reverse siphoning is a back flow of non-potable, recirculating water into a potable water
system, which can occur through the make-up float valve assembly located in the water
reservoir. Should the valve malfunction, blockage of the overflow or outlet lines would cause
water level to rise in the reservoir, and the make-up water pressure could drop below the
atmospheric pressure creating a vacuum at the make-up inlet. Although precautions to
prevent reverse siphoning are incorporated in the cooling tower design, we also recommend
installing a check valve in the water make-up supply line, as a backup precaution.
Electric Immersion Heater
Cooling towers can be ordered with an anti-freeze immersion heater systems, which consist of a
6KW heating element, water level sensor, adjustable thermostat and contactor. Components are
factory installed, but will require field wiring.
Thermostatic On/Off Control
A thermostatically controlled fan for on/off operation, should be considered as an energy saving
feature, for capacity control during winter operation. The thermostatic control can be field set to
insure automatic fan shut-down when cold water drops below design temperatures, as well as fan
start-up when cold water rises to design temperature.
A thermostatic control provides excellent cooling tower anti-freeze protection while reducing
operating costs throughout cold weather operation.