Danfoss VLT FC 102 Series Design Manual page 26

Introduction to VLT® HVAC D...
2 2
Figure 2.12 Discharge dampers reduce power consumption
somewhat. Inlet guide vans offer a 40% reduction but are
expensive to install. The Danfoss adjustable frequency drive
solution reduces energy consumption with more than 50%
and is easy to install.
2.7.5 Example with Varying Flow over 1
Year
The example below is calculated on the basis of 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 payback
period depends on the price per kWh and price of
adjustable frequency drive. In this example, it is less than a
year when compared with valves and constant speed.
Flow distribution over 1 year
P =P
shaft shaft output
[h] t
2000
1500
1000
500
100
Table 2.6 Energy Savings
24
Q
200 300 400
[m 3 /h]
Danfoss A/S © Rev. 06/2014 All rights reserved.
Design Guide
Figure 2.13 Example with Varying Flow
3
m /
h
% Hours Power Consumption
350 5
300 15
250 20
200 20
150 20
100 20
Σ 100 8760
Table 2.7 Consumption
2.7.6 Better Control
If an adjustable frequency drive is used for controlling the
flow or pressure of a system, improved control is obtained.
An adjustable frequency drive can vary the speed of the
fan or pump, thereby obtaining variable control of flow
and pressure.
Furthermore, an adjustable frequency drive 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 PID control.
Distri- Valve regulation
bution
A –B kWh
1 1
438 42.5 18.615
1314 38.5 50.589
1752 35.0 61.320
1752 31.5 55.188
1752 28.0 49.056
1752 23.0 40.296
275.064
Adjustable frequency
drive control
Power Consump-
tion
A –C kWh
1 1
42.5 18.615
29.0 38.106
18.5 32.412
11.5 20.148
6.5 11.388
3.5 6.132
26.801
MG11BC22