Specifications

2.7.17 Cooling Tower Fan

Cooling Tower Fans are used to 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 onto 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.

2.7.18 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.

Several features of the Danfoss HVAC dedicated frequency converter, the HVAC frequency converter can be utilised to

improve the performance of a cooling tower fans application. As the cooling tower fans drop below a certain speed, the

effect the fan has on cooling the water becomes small. Also, when utilising a gear-box to frequency control the tower fan, a

minimum speed of 40-50% may be 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, program the frequency converter to enter a “sleep” mode and stop the fan until a higher speed

is required. Additionally, some cooling tower fans have undesireable frequencies that may cause vibrations. These

frequencies can easily be avoided by programming the bypass frequency ranges in the frequency converter.

Introduction to VLT® HVAC D... Design Guide

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