Danfoss VLT Series Design Manual page 21

VLT ® HVAC Drive Design Guide
2.6.4. Example with varying flow over 1 year
The example below is calculated on the basis of pump characteristics obtained from a pump da-
tasheet.
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 the price of the adjustable frequency
drive. In this example, it is less than a year when compared with valves and constant speed.
Pump characteristics
m 3 /h
350
300
250
200
150
100
Σ
Distribution Valve regulation
% Hours Power
A - B
1 1
5 438 42,5
15 1314 38,5
20 1752 35,0
20 1752 31,5
20 1752 28,0
20 1752 23,0
100 8760
MG.11.B4.22 - VLT ® is a registered Danfoss trademark.
2. Introduction to the VLT HVAC Drive
Energy savings
P =P
shaft shaft output
Flow distribution over 1 year
Adjustable frequency drive
Consumption Power
kWh A - C
1
18.615 42,5
50.589 29,0
61.320 18,5
55.188 11,5
49.056 6,5
40.296 3,5
275.064
control
Consumption
kWh
1
18.615
38.106
32.412
20.148
11.388
6.132
26.801
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