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9-Blade Wheel 12-Blade Wheel
Octave Band
Sound Power (dB)
1 2 3 4 5 6 7 8 LwA
100
90
80
70
Sound Performance
Figures 2 and 3 show the inlet and outlet sound
spectrums for the size 33 unit used in the above
performance comparison.
Lower Sound Power (LwA)
The overall A-weighted sound power levels for
identical performance requirements show that the
12-bladed wheel design is quieter.
Easy to Attenuate
High sound power levels in the first and second
octave bands are difficult to attenuate. The 12-bladed
wheel generates less low frequency sound power.
Improved Sound Quality
A sound spectrum with a dominant tone can be
annoying to a listener. Greenheck’s 12-bladed wheel
provides balanced sound power levels across the
octave bands. This results in sound that is pleasing to
the listener.
Air Performance
Figure 1 plots the fan performance and efficiency of
two fans running at the same rpm. Increased wheel
efficiency allows the 12-bladed fan to produce more
airflow while using less energy.
9-Blade Wheel 12-Blade Wheel
Octave Band
Sound Power (dB)
1 2 3 4 5 6 7 8 LwA
100
90
80
70
Figure 1
Figure 2
Figure 3
8
7
6
5
4
3
2
1
0
80%
70%
60%
50%
40%
30%
20%
10%
0%
Static Pressure (in. wg)
Static Efficiency
0 5 10 15 20 25 30 35
Volume (cfm x 1000)
9-Blade Wheel
12-Blade Wheel
RPM
Efficiency
Air Performance Comparison
Size 33 @ 1400 RPM
Inlet Sound Comparison - Size 33
Outlet Sound Comparison - Size 33
Advantages of 12-Blade Wheels
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performance is adequate, recent industry trends have seen the emergence
of 12-blade wheel designs where customers demand higher mechanical
efficiency and lower sound levels.
Model QEM and QEP plenum fans feature a 12-blade aluminum airfoil
construction wheel. As demonstrated in Figure 1, this 12-blade design
meets customer needs by providing higher efficiency, lower sound levels
as well as lower energy consumption.
Greenheck’s 12-blade wheel design features extruded aluminum blades
up to and including size 49, while the largest sizes utilize laser cut, die-
formed aluminum blades. The two performance examples below demonstrate the
superior performance of the 12-blade design.
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Type
RPM
#SBLF
HP
Motor
HP Size
Static
Eff.
LwA
#MBEF 2607 7.76 10 96
#MBEF 2400 6.37 90
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8IFFM
Type
RPM
#SBLF
HP
Motor
HP Size
Static
Eff.
LwA
#MBEF 1469 26.9 30 96
#MBEF 1416 23.9 92
Performance Comparison
9 vs. 12-Blade Wheels
3