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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 A-3.
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 =
(
)
Inlet Velocity
2
Kti
4005
Where Kti =
Inlet Option Kt + Inlet Installation Kt
Outlet SP Loss =
(
)
Outlet Velocity
2
Kto
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 A-1, Q Fan/Super Q II Fan Kt
corrections, to determine the Kt values.
Add these values to any installation Kt
values. Use the result to select the fan.
Application
Considerations
Table A-1 — Q Fan/Super Q II Fan Installation Kt Corrections
Unducted (Plenum) Inlet*
Draw-Thru Type Design
Ducted Inlet
Turn > 3 Dia Upstream
Turn
2 Dia Upstream
Turn
1 Dia Upstream
Turn < 1 Dia Upstream
Not Recommended
Figure A-4 — Ducted Turns Near Q Fan
Table A-2 — Q Fan/Super Q II Fan Option Kt Corrections
Options
Use
Inlet Flange
Connects to bolted inlet duct
Inlet Bellmouth*
Reduces Unducted Inlet Kt
Inlet Plus Silencer
Reduces inlet noise
Inlet Screen
Protects Unducted Inlets
Outlet Screen
Protects Unducted Outlets
Outlet Flange
Connects to bolted outlet duct
Outlet Equalizer (Diffuser)
Improves SE
Outlet Plus Silencer
Reduces Outlet Noise
Outlet Flow Stabilization Screen
Reduces Outlet swirl
Outlet Backdraft Damper
Isolates fan from duct
Frequency Drive Modulation
Modulates Q Fan quietly
Belt Guard
Protects drives/belts
Motor Rails
Allows motor to be mounted
Standard Isolators
Isolates fan
Seismic Isolators
Isolates fan
*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).
15
Unducted Outlet
Blow-Thru Type Design
0.0
Ducted Outlet
-1.0
Turn > 2 Dia Downstream
Turn
1 Dia Downstream
+.8
+1.3
Turn < 1 Dia Downstream
Not Recommended
Q-Fan
X
X
X
X
X
X
X
X
X
Special
Special
X
X
X
X
+.8
0.0
+1.3
Super Q II Pressure
Fan
Drop (Kt)
0
X
-.1
X
+.1
X
+.1
+.5
0
0
X
+.1
X
+.8
Special
+.5
Special
0
0
Included
0
Included
0
Special
0
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