Danfoss VLT HVAC Drive FC 102 Design Manual page 29

Product Features
100
80
B
60
40
C
20
0 20 40 60 80
VOLUME %
Illustration 5.8 Fan Curves for Reduced Fan Volumes.
Example of energy savings
Illustration 5.9 describes the dependence of flow, pressure,
and power consumption on RPM. As seen in Illustration 5.9,
the flow is controlled by changing the RPM. Reducing the
speed only 20% from the rated speed also reduces the
flow by 20%. The flow is directly proportional to the RPM.
The consumption of electricity, however, is reduced by
50%.
If the system only runs at 100% flow a few days per year,
while the average is below 80% of the rated flow, the
amount of energy saved is even more than 50%.
Q n
1 1
Flow: =
Q n
2 2
2
H n
1 1
Pressure: =
H n
2 2
3
P n
1 1
Power: =
P n
2 2
Q Flow
Q Rated flow
1
Q Reduced flow
2
H Pressure
H Rated pressure
1
H Reduced pressure
2
Table 5.1 Laws of Proportionality Definitions
MG16C302
Design Guide
A
SYSTEM CURVE
FAN CURVE
100 120 140 160 180
P Power
P Rated power
1
P Reduced power
2
n Speed control
n Rated speed
1
n Reduced speed
2
Danfoss A/S © 11/2017 All rights reserved.
100%
80%
Flow ~n
50%
25%
12,5%
50%
Illustration 5.9 Laws of Proportionality
Comparison of energy savings
The Danfoss drive solution offers major savings compared
with traditional energy saving solutions. The drive
regulates fan speed according to thermal load on the
system and functions as a building management system
(BMS).
The graph (Illustration 5.10) shows typical energy savings
obtainable with 3 well-known solutions when fan volume
is reduced to 60%. As the graph shows, more than 50%
energy savings can be achieved in typical applications.
100
Discharge Damper Solution
80
IGV Solution
60
40
20
0
0 60 0
Volume %
Illustration 5.10 3 Common Energy Saving Systems
Discharge dampers reduce power consumption. Inlet guide
vanes offer a 40% reduction but are expensive to install.
The Danfoss drive solution reduces energy consumption by
more than 50% and is easy to install.
Pressure ~n 2
3
Power ~n
n
80% 100%
VLT Solution
60 0 60
27
5 5