Cooling Tower Fan; The Vlt Solution - Danfoss VLT HVAC Basic Drive FC 101 Design Manual

Product Overview

3.1.16 Cooling Tower Fan

Cooling tower fans cool condenser-water in water-cooled
chiller systems. Water-cooled chillers provide the most
efficient means of creating chilled water. They are as much
as 20% more efficient than air cooled chillers. Depending
on climate, cooling towers are often the most energy
efficient method of cooling the condenser-water from
chillers.
They cool the condenser water by evaporation.
The condenser water is sprayed into the cooling tower
until the cooling towers fill to increase its surface area. The
tower fan blows air through the fill and sprayed water to
aid in the evaporation. Evaporation removes energy from
the water dropping its temperature. The cooled water
collects in the cooling towers basin where it is pumped
back into the chillers condenser and the cycle is repeated.

3.1.17 The VLT Solution

With a frequency converter, the cooling towers fans can be
controlled to the required speed to maintain the
condenser-water temperature. The frequency converters
can also be used to turn the fan on and off as needed.
Water Inlet
Illustration 3.13 Cooling Tower Fan
MG18C702
Design Guide
Several features of the Danfoss HVAC dedicated frequency
converter can be utilized to improve the performance of
cooling tower fans applications. As the cooling tower fans
drop below a certain speed, the effect the fan has on
cooling the water becomes small. Also, when utilizing a
gearbox to frequency control the tower fan, a minimum
speed of 40–50% is required.
The customer programmable minimum frequency setting is
available to maintain this minimum frequency even as the
feedback or speed reference calls for lower speeds.
Also as a standard feature, the frequency converter can be
programmed to enter a sleep mode and stop the fan until
a higher speed is required. Additionally, some cooling
tower fans have undesirable frequencies that may cause
vibrations. These frequencies can easily be avoided by
programming the bypass frequency ranges in the
frequency converter.
Frequency
converter
Temperature
Sensor
BASIN
Water Outlet
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Conderser
Water pump
3
Supply
21
3