Application Considerations
The following is the procedure to use when selecting a fan for elevations and temperatures other than standard:
1
Determine the air density from Figure
2
Divide static pressure at the non- standard condition by the air density ratio.
3
Use the actual cfm and corrected static pressure to determine rpm and bhp from the fan performance tables.
4
The rpm is correct as selected.
5
The bhp must be multiplied by the air density ratio determined in step one to get the actual operating bhp.
Option and Installation Kt Corrections System effect losses due to less than ideal inlet or outlet configuration can be expressed in terms of velocity pressure by the following expression:
Inlet SP Loss =
Kti (Inlet4005Velocity )2
Where Kti =
Inlet Option Kt + Inlet Installation Kt
Outlet SP Loss =
Kto (Outlet Velocity)2
4005
Where Kto = Outlet Option Kt + Outlet Installation Kt
Kt is the loss factor for the inlet or discharge condition being considered.
It is necessary to add all of the static pressure loss determined from the above equation to the component static pressure to determine the point of duty static pressure for selection of the fan.
Fan Option Kt Corrections
The fan static pressure should be adjusted for fan options. Option pressure drops are documented as Kt losses and are handled the same way as installation Kt effects (losses). Use Table
Table
Unducted (Plenum) Inlet* |
| Unducted Outlet |
| |
0.0 | +.8 | |||
Ducted Inlet |
| Ducted Outlet |
| |
Turn > 3 Dia Upstream | Turn > 2 Dia Downstream | 0.0 | ||
Turn | 2 Dia Upstream | +.8 | Turn 1 Dia Downstream | +1.3 |
Turn | 1 Dia Upstream | +1.3 | Turn < 1 Dia Downstream |
|
Turn < 1 Dia Upstream |
| Not Recommended | ||
| Not Recommended |
|
| |
|
|
|
|
|
Figure
Table
|
|
| Super Q II | Pressure |
Options | Use | Fan | Drop (Kt) | |
Inlet Flange | Connects to bolted inlet duct | X |
| 0 |
Inlet Bellmouth* | Reduces Unducted Inlet Kt | X | X | |
Inlet Plus Silencer | Reduces inlet noise | X | X | +.1 |
Inlet Screen | Protects Unducted Inlets | X | X | +.1 |
Outlet Screen | Protects Unducted Outlets | X |
| +.5 |
Outlet Flange | Connects to bolted outlet duct | X |
| 0 |
Outlet Equalizer (Diffuser) | Improves SE | X |
| 0 |
Outlet Plus Silencer | Reduces Outlet Noise | X | X | +.1 |
Outlet Flow Stabilization Screen | Reduces Outlet swirl | X | X | +.8 |
Outlet Backdraft Damper | Isolates fan from duct | Special | Special | +.5 |
Frequency Drive Modulation | Modulates Q Fan quietly | Special | Special | 0 |
Belt Guard | Protects drives/belts | X |
| 0 |
Motor Rails | Allows motor to be mounted | X | Included | 0 |
Standard Isolators | Isolates fan | X | Included | 0 |
Seismic Isolators | Isolates fan | X | Special | 0 |
*Note: Bellmouth effect included in unducted installation Kt correction. Fan sizes 49 through 60 fan curves are cataloged with inlet bells. For unducted inlets without bells on size 49 through 60 fans add .1 to the inlet Kt given above.
Inlet vane losses are covered in the Selection Procedure with air density corrections (page 20).
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