Product Overview; Advantages; Why Use A Frequency Converter For Controlling Fans And Pumps; The Clear Advantage - Energy Savings - Danfoss VLT HVAC Basic Drive FC 101 Design Manual

Product Overview

3 Product Overview

3.1 Advantages

3.1.1 Why use a Frequency Converter for
Controlling Fans and Pumps?
A frequency converter takes advantage of the fact that
centrifugal fans and pumps follow the laws of propor-
tionality for such fans and pumps. For further information,
see chapter 3.1.3 Example of Energy Savings.

3.1.2 The Clear Advantage - Energy Savings

The clear advantage of using a frequency converter for
controlling the speed of fans or pumps lies in the
electricity savings.
When comparing with alternative control systems and
technologies, a frequency converter is the optimum energy
control system for controlling fan and pump systems.
100
80
B
60
40
C
20
0 20 40 60 80
VOLUME %
Illustration 3.1 Fan Curves (A, B, and C) for Reduced Fan
Volumes
MG18C702
Design Guide
A
SYSTEM CURVE
FAN CURVE
100 120 140 160 180
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120
100
80
B
60
40
C
20
0
20 40 60 80
Volume %
120
100
80
60
40
ENERGY
20
CONSUMED
0 20 40 60 80
Volume %
Illustration 3.2 Energy Savings with Frequency Converter
Solution
When using a frequency converter to reduce fan capacity
to 60% - more than 50% energy savings may be obtained
in typical applications.

3.1.3 Example of Energy Savings

As shown in Illustration 3.3, the flow is controlled by
changing the RPM. By reducing the speed by only 20%
from the rated speed, the flow is also reduced by 20%.
This is because the flow is directly proportional to the
RPM. The consumption of electricity, however, is reduced
by 50%.
If the system in question only needs to be able to supply a
flow that corresponds to 100% a few days in a year, while
the average is below 80% of the rated flow for the
remainder of the year, the amount of energy saved is even
more than 50%.
Illustration 3.3 describes the dependence of flow, pressure,
and power consumption on RPM.
A
SYSTEM CURVE
FAN CURVE
100 120 140 160 180
100 120 140 160 180
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