Single-Width Centrifugal Fan Performance Supplement - Greenheck

5
Engineering Data
Inlet Vane Performance
As inlet vanes are closed, they impart a spin to the airflow in the direction of wheel rotation and reduce airflow, static pressure and brake
horsepower as shown in the graphs below. The graphs show how CFM, static pressure and brake horsepower are affected as inlet vanes
are modulated from 100% open to 0% open in a typical variable air volume system. Graph 3 provides RPM and BHP correction factors for
fans equipped with inlet vanes.
% Peak Static Pressure
100
90
80
70
60
50
40
30
20
10
0
0 10 20 30 40 50 60 70 80 90 100
0% Open
25% Open
50% Open
% Wide Open Volume
75% Open
100% Open
Without Vanes
Graph 1 Graph 2
RPM & BHP Corrections
To compensate for pressure drop through inlet vanes, a
percentage increase in fan RPM and BHP at full-load design
conditions must be applied.
Enter graph 3 with “% wide open volume” (see page 9 for
calculation of % WOV) and the appropriate fan size.
Move horizontally left to the “% increase” scale. Record the
% increase.
Increase the selected fan RPM by the % increase shown.
Also increase the BHP by the % increase shown.
% Increase
% Peak Brake Horsepower
Graph 3
100
90
80
70
60
50
40
30
20
10
0
25% Open
0 10 20 30 40 50 60 70 80 90 100
% Wide Open Volume
50% Open
75% Open
RPM and BHP Correction Factors for Fans with Inlet Vanes
BHP Fan Sizes 12-22
BHP Fan Sizes 24-73
RPM Fan Sizes 12-22
RPM Fan Sizes 24-73
®
Without Vanes
100% Open
20
18
16
14
12
10
8
6
4
2
0
50 60 70 80 90 100
% Wide Open Volume (without vanes)
Minimum Recommended Actuator Torque For Inlet Vanes (inch-lbs.) for Single-Width Fans
Use the table below to determine minimum torque required for an inlet vane actuator.
Class
12 13 15 16 18 20 22 24
Fan Size
27 30 33 36 40 44 49 54 60 66 73
I 26 30 33 38 47 57 68 110 130 140 160 180 270 320 370 430 500 600 700
II 38 43 49 58 73 88 110 160 180 200 230 260 420 490 580 680 800 960 1100
III 54 63 72 86 110 130 160 220 260 280 330 380 620 740 880 1000 1200 1500 1700