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TRG-TRC013-EN 51
period three
Fan Capacity Control
notes
These curves describe the performance characteristics of various methods of
fan capacity control, in terms of the input power required versus the percent of
design airflow. Realize that these are generalized curves based on a given set of
test conditions.
Generally, the forward-curved (FC) centrifugal fan with inlet vanes, the variable-
pitch vaneaxial (VPVA) fan, and the fan-speed control are similar in
performance. To more accurately compare the various fan types and capacity-
control methods for a specific application, a life-cycle cost analysis should be
performed.
Fan Control Comparison
100
100
90
90
80
80
70
70
60
60
50
50
40
40
30
30
20
20
10
10
0
0
10
10
20
20
30
30
40
40
50
50
60
60
70
70
80 90 100
80 90 100
BI fan with
BI fan with
discharge
discharge
dampers
dampers
AF fan with
AF fan with
inlet vanes
inlet vanes
FC fan with
FC fan with
discharge
discharge
dampers
dampers
FC fan with
FC fan with
inlet vanes
inlet vanes
fan-speed
fan-speed
control
control
% design airflow
% design airflow
% design power
% design power
variable-pitch
variable-pitch
vaneaxial
vaneaxial
Figure 75