Specifications
130BA779.11
0 60 0 60 0 60
0
20
40
60
80
100
Discharge Damper Solution
IGV Solution
VLT Solution
Energy consumed
Energy consumed
Energy consumed
Input power %
Volume %
Illustration 2.5 Energy Savings
Discharge dampers reduce power consumption somewhat.
Inlet Guide Vans offer a 40% reduction but are expensive
to install. The Danfoss frequency converter solution
reduces energy consumption with more than 50% and is
easy to install.
2.6.5
Example with Varying Flow over 1
Year
This example is calculated based on pump characteristics
obtained from a pump datasheet.
The result obtained shows energy savings in excess of 50%
at the given flow distribution over a year. The pay back
period depends on the price per kWh and price of
frequency converter. In this example it is less than a year
when compared with valves and constant speed.
Energy savings
P
shaft
=P
shaft output
Illustration 2.6 Flow Distribution over 1 Year
175HA209.11
60
50
40
30
20
10
H
s
0 100 200 300 400
(mwg)
B
C
A
750rpm
1050rpm
1350rpm
1650rpm
0
10
20
30
(kW)
40
50
60
200100 300
(m
3
/h)
(
m
3
/h)
400
750rpm
1050rpm
1350rpm
1650rpm
P
shaft
C
1
B
1
A
1
Illustration 2.7 Energy
m
3
/
h
Distri-
bution
Valve regulation Frequency converter
control
% Hours Power Consump-
tion
Power Consump-
tion
A
1
- B
1
kWh A
1
- C
1
kWh
350 5 438 42.5 18.615 42.5 18.615
300 15 1314 38.5 50.589 29.0 38.106
250 20 1752 35.0 61.320 18.5 32.412
200 20 1752 31.5 55.188 11.5 20.148
150 20 1752 28.0 49.056 6.5 11.388
100 20 1752 23.0 40.296 3.5 6.132
Σ
100 8760 275.064 26.801
Table 2.4 Result
2.6.6
Better Control
If a frequency converter is used for controlling the flow or
pressure of a system, improved control is obtained.
A frequency converter can vary the speed of the fan or
pump, obtaining variable control of flow and pressure.
Furthermore, a frequency converter can quickly adapt the
speed of the fan or pump to new flow or pressure
conditions in the system.
Simple control of process (Flow, Level or Pressure) utilising
the built-in PI control.
Product Overview
VLT
®
HVAC Basic Drive FC 101 Design Guide
14 MG18C502 - Rev. 2013-09-06
22