Example With Varying Flow Over 1 Year; Better Control - Danfoss VLT HVAC Basic Drive FC 101 Design Manual

Product Overview
3.1.5 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 of more than
50% at the given flow distribution over a year. The
payback period depends on the price per kWh and the
price of frequency converter. In this example, it is less than
a year when compared with valves and constant speed.
Energy savings
P = P
shaft shaft output
[h] t
2000
1500
1000
500
100 200
Illustration 3.6 Flow Distribution over 1 Year
MG18C702
Design Guide
Q
300 400
[m 3 /h]
Danfoss A/S © 04/2016 All rights reserved.
H
(mwg)
s
60
50
B
40
30
20
C
10
750rpm
0 100 200
P
(kW)
shaft
60
50
40
30
B 1
20
10
1050rpm
C 1
750rpm
0 100 200
Illustration 3.7 Energy
m 3 / Distri-
Valve regulation
bution
h
Consump-
% Hours Power
A - B
1 1
350 5 438 42.5
300 15 1314 38.5
250 20 1752 35.0
200 20 1752 31.5
150 20 1752 28.0
100 20 1752 23.0
Σ
100 8760 – 275.064
Table 3.2 Result

3.1.6 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) utilizing
the built-in PI control.
A
1650rpm
1350rpm
1050rpm
( 3 )
m /h
300 400
A 1
1650rpm
1350rpm
( )
300 400 m 3 /h
Frequency converter
control
Consump-
Power
tion tion
kWh A - C kWh
1 1
18.615 42.5 18.615
50.589 29.0 38.106
61.320 18.5 32.412
55.188 11.5 20.148
49.056 6.5 11.388
40.296 3.5 6.132
– 26.801
15
3 3