Danfoss FC 101 Design Guide

2.6.16 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.
2.6.17
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.
Several features of the Danfoss HVAC dedicated frequency
converter, the HVAC frequency converter can be utilised 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 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, 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 undesireable frequencies that may cause
vibrations. These frequencies can easily be avoided by
programming the bypass frequency ranges in the
frequency converter.
Frequency
converter
Water Inlet
Water Outlet
CHILLER
Temperature
Sensor
BASIN
Conderser
Water pump
Supply
130BB453.10
Illustration 2.13 Cooling Tower Fan
Product Overview
VLT
®
HVAC Basic Drive FC 101 Design Guide
20 MG18C502 - Rev. 2013-09-06
22

Danfoss FC 101 Specifications

General

Model	FC 101
Manufacturer	Danfoss
Protection Class	IP20
Relative Humidity	95% (non-condensing)
Communication Interface	RS-485