Danfoss VLT HVAC Drive FC 100 Series Design Manual page 16

2. Introduction to VLT HVAC Drive
The laws of proportionality
The figure below describes the dependence of flow, pressure and power consumption on rpm.
Q = Flow
2
Q = Rated flow
1
Q = Reduced flow
2
H = Pressure
H = Rated pressure
1
H = Reduced pressure
2
2.6.4. Comparison of energy savings
The Danfoss frequency converter solution offers major savings compared
with traditional energy saving solutions. This is because the frequency
converter is able to control fan speed according to thermal load on the
system and the fact that the frequency converter has a build-in facility
that enables the frequency converter to function as a Building Manage-
ment System, BMS.
The graph below illustrates typical energy savings obtainable with 3 well-
known solutions when fan volume is reduced to i.e. 60%.
As the graph shows, more than 50% energy savings can be achieved in
typical applications.
16
P = Power
P = Rated power
1
P = Reduced power
2
n = Speed regulation
n = Rated speed
1
n = Reduced speed
2
Q
1
Flow
:
Q
2
Pressure
:
P
1
Power :
P
2
Illustration 2.3: The three common energy saving systems.
MG.11.B7.02 - VLT ® is a registered Danfoss trademark
®
VLT HVAC Drive Design Guide
n
1
=
n
2
( )
H n 2
1 1
=
H n
2 2
( )
n
3
1
=
n
2