Download - AMCA Publication 201-02 (R2007)
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The International Authority on Air System Components
AIR MOVEMENT AND CONTROLASSOCIATION INTERNATIONAL, INC.
AMCAPublication 201-02
Fans and Systems
(R2007)
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AMCA PUBLICATION 201-02 (R2007)
Fans and Systems
Air Movement and Control Association International, Inc.
30 West University Drive
Arlington Heights, IL 60004-1893
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2007 by Air Movement and Control Association International, Inc.
All rights reserved. Reproduction or translation of any part of this work beyond that permitted by Sections 107 and
108 of the United States Copyright Act without the permission of the copyright owner is unlawful. Requests for
permission or further information should be addressed to the Executive Director, Air Movement and Control
Association International, Inc. at 30 West University Drive, Arlington Heights, IL 60004-1893 U.S.A.
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Forward
ANSI/AMCA Standard 210 Laboratory Methods of Testing Fans for Aerodynamic Performance Rating, provides abasis for accurately rating the performance of fans when tested under standardized laboratory conditions. Theactual performance of a fan when installed in an air moving system will sometimes be different from the fanperformance as measured in the laboratory. The difference in performance between the laboratory and the fieldinstallation can sometimes be attributed to the interaction of the fan and the duct system, i.e., duct system designcan diminish the usable output of the fan.
AMCA Publication 201 Fans and Systems, introduced the concept of System Effect Factor to the air movingindustry. The System Effect Factor quantifies the duct system design effect on performance. The System EffectFactor has been widely accepted since its inception in 1973. It must be remembered, however, that the "factors"provided are approximations as it is prohibitive to test all fan types and all duct system configurations. The majorrevision to this edition of AMCA Publication 201 Fans and Systems, is a change to the use of SI units of measure,with Inch-Pound units being given secondary consideration.
AMCA 201 Review Committee
Bill Smiley The Trane Company / LaCrosse
James L. Smith Aerovent, A Twin City Fan Company
Tung Nguyen Emerson Ventilation Products
Patrick Chinoda Hartzell Fan, Inc.
Rick Bursh Illinois Blower, Inc.
Sutton G. Page Austin Air Balancing Corp.
Paul R. Saxon AMCA Staff
Disclaimer
AMCA International uses its best efforts to produce standards for the benefit of the industry and the public in lightof available information and accepted industry practices. However, AMCA International does not guarantee, certifyor assure the safety or performance of any products, components or systems tested, designed, installed oroperated in accordance with AMCA International standards or that any tests conducted under its standards will benon-hazardous or free from risk.
Objections to AMCA Standards and Certifications Programs
Air Movement and Control Association International, Inc. will consider and decide all written complaints regardingits standards, certification programs, or interpretations thereof. For information on procedures for submitting andhandling complaints, write to:
Air Movement and Control Association International30 West University DriveArlington Heights, IL 60004-1893 U.S.A.
or
AMCA International, Incorporatedc/o Federation of Environmental Trade Associations2 Waltham Court, Milley Lane, Hare HatchReading, BerkshireRG10 9TH United Kingdom
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Related AMCA Standards and Publications
Publication 200 AIR SYSTEMS
System Pressure Losses
Fan Performance Characteristics
System Effect
System Design Tolerances
Air Systems is intended to provide basic information needed to design effective and energy efficient air systems.Discussion is limited to systems where there is a clear separation of the fan inlet and outlet and does not cover
applications in which fans are used only to circulate air in an open space.
Publication 201 FANS AND SYSTEMS
Fan Testing and Rating
The Fan "Laws"
Air Systems
Fan and System Interaction
System Effect Factors
Fans and Systems is aimed primarily at the designer of the air moving system and discusses the effect on inlet andoutlet connections of the fan's performance. System Effect Factors, which must be included in the basic design
calculations, are listed for various configurations. AMCA 202 and AMCA 203 are companion documents.
Publication 202 TROUBLESHOOTING
System Checklist
Fan Manufacturer's Analysis
Master Troubleshooting Appendices
Troubleshooting is intended to help identify and correct problems with the performance and operation of the airmoving system after installation. AMCA 201 and AMCA 203 are companion documents.
Publication 203 FIELD PERFORMANCE MEASUREMENTS OF FAN SYSTEMS
Acceptance Tests
Test Methods and Instruments
Precautions
Limitations and Expected Accuracies
Calculations
Field Performance Measurements of Fan Systems reviews the various problems of making field measurementsand calculating the actual performance of the fan and system. AMCA 201 and AMCA 202 are companion
documents.
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TABLE OF CONTENTS
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1.2 Some limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2. Symbols and Subscripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2.1 Symbols and subscripted symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
2.2 Subscripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
3. Fan Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
3.1 ANSI/AMCA Standard 210 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
3.2 Ducted outlet fan tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
3.3 Free inlet, free outlet fan tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
3.4 Obstructed inlets and outlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
4. Fan Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
4.1 The Fan Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
4.2 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
4.3 Fan performance curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
5. Catalog Performance Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
5.1 Type A: Free inlet, free outlet fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
5.2 Ducted fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
6. Air Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
6.1 The system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
6.2 Component losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
6.3 The system curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
6.4 Interaction of system curve and fan performance curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
6.5 Effect of changes in speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
6.6 Effect of density on system resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
6.7 Fan and system interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
6.8 Effects of errors in estimating system resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
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6.9 Safety factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
6.10 Deficient fan/system performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
6.11 Precautions to prevent deficient performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
6.12 System effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
7. System Effect Factor (SEF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
7.1 System Effect Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
7.2 Power determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
8. Outlet System Effect Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
8.1 Outlet ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
8.2 Outlet diffusers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
8.3 Outlet duct elbows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
8.4 Turning vanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
8.5 Volume control dampers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
8.6 Duct branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
9. Inlet System Effect Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
9.1 Inlet ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
9.2 Inlet duct elbows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
9.3 Inlet vortex (spin or swirl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
9.4 Inlet turning vanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
9.5 Airflow straighteners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
9.6 Enclosures (plenum and cabinet effects) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
9.7 Obstructed inlets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
10. Effects of Factory Supplied Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
10.1 Bearing and supports in fan inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
10.2 Drive guards obstructing fan inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
10.3 Belt tube in axial fan inlet or outlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
10.4 Inlet box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
10.5 Inlet box dampers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
10.6 Variable inlet vane (VIV) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
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Annex A. SI / I-P Conversion Table (Informative) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Annex B. Dual Fan Systems - Series and Parallel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
B.1 Fans operating in series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
B.2 Fans operating in parallel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Annex C. Definitions and Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
C.1 The air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
C.2 The fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
C.3 The system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
Annex D. Examples of the Convertibility of Energy from Velocity
Pressure to Static Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
D.1 Example of fan (tested with free inlet, ducted outlet) applied to a
duct system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
D.2 Example of fan (tested with free inlet, ducted outlet), connected to a
duct system and then a plenum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
D.3 Example of fan with free inlet, free outlet - fan discharges directly
into plenum and then to duct system (abrupt expansion at fan outlet) . . . . . . . . . . . . . . . . . . .65
D.4 Example of fan used to exhaust with obstruction in inlet, inlet elbow,
inlet duct, free outlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
Annex E. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
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AMCA INTERNATIONAL, INC. AMCA 201-02 (R2007)
Fans and Systems
1. Introduction
ANSI/AMCA 210 Laboratory Methods of Testing FansFor Aerodynamic Performance Rating, offers thesystem design engineer guidance as to how the fan
was tested and rated. AMCA Publication 201 Fansand Systems, helps provide guidance as to whateffect the system and its connections to the fan have
on fan performance.
Recognizing and accounting for losses that affect the
fans performance, in the design stage, will allow the
designer to predict with reasonable accuracy, the
installed performance of the fan.
1.1 Purpose
This part of the AMCA Fan Application Manualincludes general information about how fans are
tested in the laboratory, and how their performance
ratings are calculated and published. It also reviews
some of the more important reasons for the "loss" of
fan performance that may occur when the fan is
installed in an actual system.
Allowances, called System Effect Factors (SEF), arealso given in this part of the manual. SEF must betaken into account by the system design engineer if a
reasonable estimate of fan/system performance is to
be determined.
1.2 Some limitations
It must be appreciated that the System Effect Factorsgiven in this manual are intended as guidelines and
are, in general, approximations. Some have been
obtained from research studies, others have been
published previously by individual fan manufacturers,
and many represent the consensus of engineers with
considerable experience in the application of fans.
Fans of different types and even fans of the same
type, but supplied by different manufacturers, will not
necessarily react with the system in exactly the same
way. It will be necessary, therefore, to apply judgment
based on actual experience in applying the SEF.
The SEF represented in this manual assume that thefan application is generally consistent with the
method of testing and rating by the manufacturer.
Inappropriate application of the fan will result in SEF
values inconsistent with the values presented.
Mechanical design of the fan is not within the scope
of this publication.
2. Symbols and Subscripts
For symbols and subscripted symbols, see Table 2.1.
For subscripts, see Table 2.2.
3. Fan Testing
Fans are tested in setups that simulate installations.
The four standard installation types are as shown in
Figure 3.1.
Figure 3.1 - Standard Fan Installation Types
3.1 ANSI/AMCA Standard 210
Most fan manufacturers rate the performance of their
products from tests made in accordance with
ANSI/AMCA 210 Laboratory Methods of Testing Fansfor Aerodynamic Performance Rating. The purpose
AMCA INSTALLATION TYPE A:Free Inlet, Free Outlet
AMCA INSTALLATION TYPE B:Free Inlet, Ducted Outlet
AMCA INSTALLATION TYPE C:Ducted Inlet, Free Outlet
AMCA INSTALLATION TYPE D:Ducted Inlet, Ducted Outlet
1
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Table 2.1 - Symbols and Subscripted Symbols
UNITS OF MEASURE
SYMBOL DESCRIPTION SI I-P
A Area of cross section m2 ft2
D Diameter, impeller mm in.
D Diameter, Duct m ft
H Fan Power Input kw hp
H/T Hub-to-Tip Ratio Dimensionless
Kp Compressibility Coefficient Dimensionless
Cp Loss Coefficient Dimensionless
N Speed of Rotation rpm rpm
Ps Fan Static Pressure Pa in. wg
Pt Fan Total Pressure Pa in. wg
Pv Fan Velocity Pressure Pa in. wg
pb Corrected Barometric Pressure kPa in. Hg
PL Plane of Measurement --- ---
Q Airflow m3/s ft3/min
Re Fan Reynolds Number Dimensionless
SEF System Effect Factor Pa in. wg
td Dry-Bulb Temperature C F
tw Wet-Bulb Temperature C F
Air Viscosity Pas lbm/fts
V Velocity m/s fpm
W Power Input to Motor watts watts
s Fan Static Efficiency % %
t Fan Total Efficiency % %
Air Density kg/m3 lbm/ft3
Table 2.2 - Subscripts
SUBSCRIPT DESCRIPTION
a Atmospheric conditions
c Converted Value
x Plane 0, 1, 2, ...as appropriate
1 Fan Inlet Plane
2 Fan Outlet Plane
3 Pitot Traverse Plane
5 Plane 5 (nozzle inlet station in chamber)
6 Plane 6 (nozzle discharge station in chamber)
8 Plane 8 (inlet chamber measurement station)
AMCA 201-02 (R2007)
2
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TransitionPiece
Straightener
1 2
FOR FAN INSTALLATION TYPES:
B: Free Inlet, Ducted Outlet D: Ducted Inlet, Ducted Outlet
Figure 3.2 - Pitot Traverse in Outlet Duct
AMCA 201-02 (R2007)
of ANSI/AMCA 210 is to establish uniform methods
for laboratory testing of fans and other air moving
devices to determine performance in terms of airflow,
pressure, power, air density, speed of rotation and
efficiency, for rating or guarantee purposes. Two
methods of measuring airflow are included: the Pitot
tube and the long radius flow nozzle. These are
incorporated into a number of "setups" or "figures".
In general, a fan is tested on the setup that most
closely resembles the way in which it will be installed
in an air system. Centrifugal and axial fans are
usually tested with an outlet duct. Propeller fans are
normally tested in the wall of a chamber or plenum.
Power roof ventilators (PRV) are tested mounted on
a curb exhausting from the test chamber.
It is very important to realize that each setup in
ANSI/AMCA 210 is a standardized arrangement that
is not intended to reproduce exactly any installationlikely to be found in the field. The infinite variety of
possible arrangements of actual air systems makes it
impractical to duplicate every configuration in the fan
test laboratory.
3.2 Ducted outlet fan tests
Figure 3.2 is a reproduction of a test setup from
ANSI/AMCA 210. Note that this particular setup
includes a long straight duct connected to the outlet
of the fan. A straightener is located upstream of the
Pitot traverse to remove swirl and rotational
components from the airflow and to ensure that
airflow at the plane of measurement is as nearly
uniform as possible.
The angle of the transition between the test duct and
the fan outlet is limited to ensure that uniform airflow
will be maintained. A steep transition, or abrupt
change of cross section would cause turbulence and
eddies. The effect of this type of airflow disturbance
at the fan outlet is discussed later.
Uniform airflow conditions ensure consistency and
reproducibility of test results and permit the fan to
develop its maximum performance. In any installationwhere uniform airflow conditions do not exist, thefan's performance will be measurably reduced.
As illustrated in Figure 3.3 Plane 2, the velocity
profile at the outlet of a fan is not uniform. The section
of straight duct attached to the fan outlet controls the
diffusion of the outlet airflow and establishes a more
uniform velocity as shown in Figure 3.3 Plane X.
The energy loss when a gas, such as air, passes
through a sudden enlargement is related to the
square of the velocity. Thus the ducted outlet with its
more uniform velocity significantly reduces the loss at
the point of discharge to the atmosphere.
A manufacturer may test a fan with or without an inlet
duct or outlet duct. For products licensed to use the
AMCA Certified Ratings Seal, catalog ratings will
state whether ducts were used during the rating tests.
If the fans are not to be applied with the same duct(s)
as in the test setup, an allowance should be made for
the difference in performance that may result.
3
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43.3 Free inlet, free outlet fan tests
Figure 3.4 illustrates a typical multi-nozzle chamber
test setup from ANSI/AMCA 210. This simulates the
conditions under which most exhaust fans are tested
and rated. Fan performance based on this type of
test may require adjustment when additional
accessories are used with the fan. Fans designed for
use without duct systems are usually rated over a
lower range of pressures. They are commonly
cataloged and sold as a complete unit with suitable
drive and motor.
3.4 Obstructed inlets and outlets
The test setups in ANSI/AMCA 210 result in
unobstructed airflow conditions at both the inlet and
the outlet of the fan. Appurtenances or obstructions
located close to the inlet and/or outlet will affect fan
performance. Shafts, bearings, bearing supports and
other appurtenances normally used with a fan should
be in place when a fan is tested for rating.
Variations in construction which may affect fan
performance include changes in sizes and types of
sheaves and pulleys, bearing supports, bearings and
shafts, belt guards, inlet and outlet dampers, inlet
vanes, inlet elbows, inlet and outlet cones, and
cabinets or housings.
Since changes in performance will be different for
various product designs, it will be necessary to make
suitable allowances based on data obtained from the
applicable fan catalog or directly from the
manufacturer.
Most single width centrifugal fans are tested using
Arrangement 1 fans. Some allowance for the effect
of bearings and bearing supports in the inlet may be
necessary when using Arrangement 3 or
Arrangement 7. The various AMCA standard
arrangements are shown on Figures 3.5, 3.6, and
3.7.
4. Fan Ratings
4.1 The Fan Laws
It is not practical to test a fan at every speed at which
it may be applied. Nor is it possible to simulate every
inlet density that may be encountered. Fortunately,
by use of a series of equations commonly referred to
as the Fan Laws, it is possible to predict with good
accuracy the performance of a fan at other speeds
and densities than those of the original rating test.
The performance of a complete series of
geometrically similar (homologous) fans can also be
calculated from the performance of smaller fans in
the series using the appropriate equations.
Because of the relationship between the airflow,
pressure and power for any given fan, each set of
equations for changes in speed, size or density,
applies only to the same Point of Rating, and all the
equations in the set must be used to define the
converted condition. A Point of Rating is the specified
fan operating point on its characteristic curve.
The Fan Law equations are shown below as ratios.
The un-subscripted variable is used to designate the
initial or test fan values for the variable and the
subscript c is used to designate the converted,
dependent or desired variable.
Qc = Q (Dc/D)3 (Nc/N) (Kp/Kpc)
Ptc = Pt (Dc/D)2 (Nc/N)2 (c/) (Kp/Kpc)
Pvc = Pv (Dc/D)2 (Nc/N)2 (c/)
Psc = Ptc - Pvc
Hc = H (Dc/D)5 (Nc/N)3 (c/) (Kp/Kpc)
tc = (Qc Ptc Kp) / Hc (SI)
tc = (Qc Ptc Kp) / (6362 Hc) (I-P)
sc = tc (Psc/Ptc)
These equations have their origin in the classical
theories of fluid mechanics, and the accuracy of the
results obtained is sufficient for most applications.
Better accuracy would require consideration of
Reynolds number, Mach number, kinematic viscosity,
dynamic viscosity, surface roughness, impeller blade
thickness and relative clearances, etc.
4.2 Limitations
Under certain conditions the properties of gases
change and there are, therefore, limitations to the use
of the Fan Laws. Accurate results will be obtained
when the following limitations are observed:
a. Fan Reynolds Number (Re). The term Reynolds
number is associated with the ratio of inertia to
viscous forces. When related to fans, investigations
of both axial and centrifugal fans show that
performance losses are more significant at low
Reynolds number ranges and are effectively
negligible above certain threshold Reynolds
numbers. In an effort to simplify the comparison of
the Reynolds numbers of two fans, the fan industry
AMCA 201-02 (R2007)
-
5AMCA 201-02 (R2007)
PL 2PL X
PL 2 PL X
OUTLET AREA
BLAST AREA
CENTRIFUGAL FAN
AXIAL FAN
CUTOFF
DISCHARGE DUCT
PL.5 PL.6 PL.8 PL.1 PL.2
SETTLINGMEANS
VARIABLESUPPLYSYSTEM
SETTLINGMEANS(See note 4)
FAN
0.1 M MIN.
0.5 M MIN.0.2 M MIN.0.3 M MIN.
P t8PP s5
M
0.2MMIN.
38mm 6mm(1.5in. 0.25 in.)
0.5MMIN.
td2
td3
AIRFLOW
Figure 3.3 - Controlled Diffusion and Establishment of a Uniform Velocity
Profile in a Straight Length of Outlet Duct
Figure 3.4 - Inlet Chamber Setup - Multiple Nozzles in Chamber
(ANSI/AMCA 210-99, Figure 15)
-
AMCA International, Inc. | 30 W. University Dr. | Arlington Heights, IL, 60004-1893 | U.S.A
ANSI/AMCA Standard 99-2404-03 Page 1 of 2
AMCA Drive
Arrangement
ISO 13349
Drive
Arrangement
Description Fan ConfigurationAlternative Fan
Configuration
1 SWSI 1 or
12 (Arr. 1 with
sub-base)
For belt or direct drive.
Impeller overhung on shaft, two
bearings mounted on pedestal
base.
Alternative: Bearings mounted
on independant pedestals, with
or without inlet box.
2 SWSI 2 For belt or direct drive.
Impeller overhung on shaft,
bearings mounted in bracket
supported by the fan casing.
Alternative: With inlet box.
3 SWSI 3 or
11 (Arr. 3 with
sub-base)
For belt or direct drive.
Impeller mounted on shaft
between bearings supported by
the fan casing.
Alternative: Bearings mounted
on independent pedestals, with
or without inlet box.
3 DWDI 6 or
18 (Arr. 6 with
sub-base)
For belt or direct drive.
Impeller mounted on shaft
between bearings supported by
the fan casing.
Alternative: Bearings mounted
on independent pedestals, with
or without inlet boxes.
4 SWSI 4 For direct drive.
Impeller overhung on motor
shaft. No bearings on fan.
Motor mounted on base.
Alternative: With inlet box.
5 SWSI 5 For direct drive.
Impeller overhung on motor
shaft. No bearings on fan.
Motor flange mounted to
casing.
Alternative: With inlet box.
Drive Arrangements for Centrifugal FansAn American National Standard - Approved by ANSI on April 17, 2003
Figure 3.5 - AMCA Standard 99-2404 / Page 1
AMCA 201-02 (R2007)
6
-
ANSI/AMCA Standard 99-2404-03 Page 2 of 2
AMCA International, Inc. | 30 W. University Dr. | Arlington Heights, IL, 60004-1893 | U.S.A
AMCA Drive
Arrangement
ISO 13349
Drive
Arrangement
Description Fan ConfigurationAlternative Fan
Configuration
7 SWSI 7 For coupling drive.
Generally the same as Arr. 3,
with base for the prime mover.
Alternative: Bearings mounted
on independent pedestals with
or without inlet box.
7DWDI 17
(Arr. 6 with
base for motor)
For coupling drive.
Generally the same as Arr. 3
with base for the prime mover.
Alternative: Bearings mounted
on independent pedestals with
or without inlet box.
8 SWSI 8 For direct drive.
Generally the same as Arr. 1
with base for the prime mover.
Alternative: Bearings mounted
on independent pedestals with
or without inlet box.
9 SWSI 9 For belt drive.
Impeller overhung on shaft, two
bearings mounted on pedestal
base.
Motor mounted on the outside
of the bearing base.
Alternative: With inlet box.
10 SWSI 10 For belt drive.
Generally the same as Arr. 9
with motor mounted inside of
the bearing pedestal.
Alternative: With inlet box.
Figure 3.6 - AMCA Standard 99-2404 / Page 2
AMCA 201-02 AMCA 201-02 (R2007)
7
-
AMCA International, Inc. | 30 W. University Dr. | Arlington Heights, IL, 60004-1893 | U.S.A
ANSI/AMCA Standard 99-3404-03 Page 1 of 1
Drive Arrangements for Axial FansAn American National Standard - Approved by ANSI on June 10, 2003
AMCA Drive
Arrangement
ISO 13349
Drive
Arrangement
Description Fan ConfigurationAlternative Fan
Configuration
1 1
12 (Arr. 1 with
sub-base)
For belt or direct drive.
Impeller overhung on shaft, two
bearings mounted either
upstream or downstream of the
impeller.
Alternative: Single stage or two
stage fans can be supplied with
inlet box and/or discharge
evas.
3 3
11 (Arr. 3 with
sub-base)
For belt or direct drive.
Impeller mounted on shaft
between bearings on internal
supports.
Alternative: Fan can be
supplied with inlet box, and/or
discharge evas.
4 4 For direct drive.
Impeller overhung on motor
shaft. No bearings on fan.
Motor mounted on base or
integrally mounted.
Alternative: With inlet box
and/or with discharge evas.
M MM M
7 7 For direct drive.
Generally the same as Arr. 3
with base for the prime mover.
Alternative: With inlet box
and/or discharge evas.
M M
8 8 For direct drive.
Generally the same as Arr. 1
with base for the prime mover.
Alternative: Single stage or two
stage fans can be supplied with
inlet box and/or discharge
evas.
M M
9 9 For belt drive.
Generally same as Arr. 1 with
motor mounted on fan casing,
and/or an integral base.
Alternative: With inlet box
and/or discharge evas
M
Note: All fan orientations may be horizontal or vertical
Figure 3.7 - AMCA Standard 99-3404 / Page 1
AMCA 201-02 (R2007)
8
-
AMCA 201-02 (R2007)
has adopted the term Fan Reynolds Number.
Re = (ND2) / (60)
where: N = impeller rotational speed, rpm D = impeller diameter, m(ft) = air density, kg/m3 (lbm/ft3) = absolute viscosity, 1.8185 10-3 Pas (5C to 38C) (SI)
(1.22 10-05 lbm/fts (40F to 100F)) (I-P)
The threshold fan Reynolds number for centrifugal
and axial fans is about 3.0 106. That is, there is a
negligible change in performance between the two
fans due to differences in Reynolds number if both
fans are operating above this threshold value. When
the Reynolds number of a model fan is below 3.0
106, there may be a gain in efficiency (size effect) for
a full size fan operating above the threshold
compared to one operating below the threshold. This
occurs only when both fans are operating near peak
efficiency. Therefore, when a model test is being
conducted to verify the rating of a full size fan, the
Reynolds number should be above 3.0 106 to avoid
any uncertainty relating to Reynolds number effects.
b. Point of Rating. To predict the performance of a
fan from a smaller model using the Fan Laws, both
fans must be geometrically similar (homologous),
and both fans must operate at the same
corresponding rating points on their characteristic
curves. Two or more fans are said to be operating at
corresponding points of rating if the positions of the
operating points, relative to the pressure at shutoff
and the airflow at free delivery, are the same.
c. Compressibility. Compressibility is the characteristic
of a gas to change its volume as a function of
pressure, temperature and composition. The
compressibility coefficient (Kp) expresses the ratio ofthe fan total pressure developed with an
incompressible fluid to the fan total pressure
developed with a compressible fluid (See
ANSI/AMCA 210). Differences in the compressibility
coefficient between two similar fans must be
calculated using the proper specific heat ratio for the
gases being handled.
d. Specific Heat Ratio (Cp). Model fan tests areusually based on air with a specific heat ratio of 1.4.
Induced draft fans may handle flue gas with a specific
heat ratio of 1.35. Even though these differences may
normally be considered small, they make a
noticeable difference in the calculation of the
compressibility coefficient. Refer to AMCA
Publication 802, Annex A, for calculation procedures.
e. Tip Speed Mach Parameter (Mt). Tip speed Machparameter is an expression relating the tip speed of
the impeller to the speed of sound at the fan inlet
condition.
When airflow velocity at a point approaches the
speed of sound, some blocking or choking effects
occur that reduce the fan performance.
4.3 Fan performance curves
A fan performance curve is a graphic presentation of
the performance of a fan. Usually it covers the entire
range from free delivery (no obstruction to airflow) to
no delivery (an air tight system with no air flowing).
One, or more, of the following characteristics may be
plotted against volume airflow (Q).
Fan Static Pressure PsFan Total Pressure PtFan Power HFan Static Efficiency sFan Total Efficiency t
Air density (), fan size (D), and fan rotational speed(N) are usually constant for the entire curve and mustbe stated.
A typical fan performance curve is shown in Figure
4.1. Figure 4.2 illustrates examples of performance
curves for a variety of fan types.
9
-
SIZE 30 FAN AT N RPM
OPERATION ATSTANDARD DENSITY
PR
ES
SU
RE
, P
PO
WE
R, H
0
10
20
30
40
50
60
70
80
90
100
AIRFLOW, Q
Pt
Ps
t
s
H EFF
ICIE
NC
Y,
PE
RC
EN
T
Figure 4.1 - Fan Performance Curve at N RPM
AMCA 201-02 (R2007)
10
-
AMCA 201-02 (R2007)
11
TYPE IMPELLER DESIGN HOUSING DESIGN
AIR
FOIL
BA
CK
WA
RD
-IN
CLI
NE
DB
AC
KW
AR
D-
CU
RV
ED
RA
DIA
LFO
RW
AR
D-
CU
RV
ED
PR
OP
ELL
ER
TUB
EA
XIA
L
AX
IAL
FAN
S
VAN
EA
XIA
L
CE
NTR
IFU
GA
L FA
NS
TUB
ULA
R
CE
NTR
IFU
GA
L
SP
EC
IAL
DE
SIG
NS
PO
WE
R R
OO
F V
EN
TILA
TOR
S
AX
IAL
CE
NTR
IFU
GA
L Highest efficiency of all centrifugal fan designs. Ten to 16 blades of airfoil contour curved away from direction of rotation. Deep blades allow for efficient expansion within blade passages Air leaves impeller at velocity less than tip speed. For given duty, has highest speed of centrifugal fan designs
Scroll-type design for efficient conversion of velocity pressure to static pressure. Maximum efficiency requires close clearance and alignment between wheel and inlet
Uses same housing configuration as airfoil design. Efficiency only slightly less than airfoil fan. Ten to 16 single-thickness blades curved or inclined away from direction of rotation Efficient for same reasons as airfoil fan.
Scroll. Usually narrowest of all centrifugal designs. Because wheel design is less efficient, housing dimensions are not as critical as for airfoil and backward-inclined fans.
Higher pressure characteristics than airfoil, backward-curved, and backward-inclined fans. Curve may have a break to left of peak pressure and fan should not be operated in this area. Power rises continually to free delivery.
Flatter pressure curve and lower efficiency than the airfoil, backward-curved, and backward-inclined. Do not rate fan in the pressure curve dip to the left of peak pressure. Power rises continually toward free delivery. Motor selection must take this into account.
Scroll similar to and often identical to other centrifugal fan designs. Fit between wheel and inlet not as critical as for airfoil and backward-inclined fans.
Simple circular ring, orifice plate, or venturi. Optimum design is close to blade tips and forms smooth airfoil into wheel.
Cylindrical tube with close clearance to blade tips.
Cylindrical tube with close clearance to blade tips. Guide vanes upstream or downstream from impeller increase pressure capability and efficiency.
Cylindrical tube similar to vaneaxial fan, except clearance to wheel is not as close. Air discharges radially from wheel and turns 90 to flow through guide vanes.
Normal housing not used, since air discharges from impeller in full circle. Usually does not include configuration to recover velocity pressure component.
Essentially a propeller fan mounted in a supporting structure Hood protects fan from weather and acts as safety guard. Air discharges from annular space at bottom of weather hood.
Low efficiency. Limited to low-pressure applications. Usually low cost impellers have two or more blades of single thickness attached to relatively small hub. Primary energy transfer by velocity pressure.
Somewhat more efficient and capable of developing more useful static pressure than propeller fan. Usually has 4 to 8 blades with airfoil or single- thickness cross section. Hub usually less than transfer by velocity pressure.
Good blade design gives medium- to high-pressure capability at good efficiency. Most efficient of these fans have airfoil blades. Blades may have fixed, adjustable, or controllable pitch. Hub is usually greater than half fan tip diameter.
Performance similar to backward-curved fan except capacity and pressure are lower. Lower efficiency than backward-curved fan. Performance curve may have a dip to the left of peak pressure.
Low-pressure exhaust systems such as general factory, kitchen, warehouse, and some commercial installations. Provides positive exhaust ventilation, which is an advantage over gravity-type exhaust units. Centrifugal units are slightly quieter than axial units.
Low-pressure exhaust systems such as general factory, kitchen, warehouse, and some commercial installations. Provides positive exhaust ventilation, which is an advantage over gravity-type exhaust units.
R
M
A
B
R
M
Figure 4.2 - Types of Fans
Adapted with permission from 1996 ASHRAE Systems and Equipment Handbook (SI)
-
12
AMCA 201-02 (R2007)
Figure 4.2 - Types of Fans
Adapted with permission from 1996 ASHRAE Systems and Equipment Handbook (SI)
PERFORMANCE CHARACTERISTICS APPLICATIONSPERFORMANCE CURVES a
Similar to airfoil fan, except peak efficiency slightly lower.
Higher pressure characteristics than airfoil and backward- curved fans. Pressure may drop suddenly at left of peak pressure, but this usually causes no problems. Power rises continually to free delivery.
Pressure curve less steep than that of backward-curved fans. Curve dips to left of peak pressure. Highest efficiency to right of peak pressure at 40 to 50% of wide open volume. Rate fan to right of peak pressure. Account for power curve, which rises continually toward free delivery, when selecting motor.
High flow rate, but very low-pressure capabilities. Maximum efficiency reached near free delivery. Discharge pattern circular and airstream swirls.
High flow rate, medium-pressure capabilities. Performance curve dips to left of peak pressure. Avoid operating fan in this region. Discharge pattern circular and airstream rotates or swirls.
High-pressure characteristics with medium-volume flow capabilities. Performance curve dips to left of peak pressure due to aerodynamic stall. Avoid operating fan in this region. Guide vanes correct circular motion imprated by wheel and improve pressure characteristics and efficiency of fan.
Usually operated without ductwork; therefore, operates at very low pressure and high volume. Only static pressure and static efficiency are shown for this fan.
Usually operated without ductwork; therefore, operates at very low pressure and high volume. Only static pressure and static efficiency are shown for this fan.
Low-pressure exhaust systems, such as general factory, kitchen, warehouse, and some commercial installations. Low first cost and low operating cost give an advantage over gravity flow exhaust systems.
Has straight-through flow.
Primarily for low-pressure, return air systems in HVAC applications.
General HVAC systems in low-, medium-, and high-pressure applications where straight-through flow and compact installation are required. Has good downstream air distribution Used in industrial applications in place of tubeaxial fans. More compact than centrifugal fans for same duty.
Low-pressure exhaust systems, such as general factory, kitchen, warehouse, and some commercial installations. Low first cost and low operating cost give an advantage over gravity flow exhaust systems. Centrifugal units are somewhat quieter than axial flow units.
Low- and medium-pressure ducted HVAC applications where air distribution downstream is not critical. Used in some industrial applications, such as drying ovens, paint spray booths, and fume exhausts.
For low-pressure, high-volume air moving applications, such as air circulation in a space or ventilation through a wall without ductwork. Used for makeup air applications.
Primarily for low-pressure HVAC applications, such as residential furnaces, central station units, and packaged air conditioners.
Primarily for materials handling in industrial plants. Also for some high-pressure industrial requirements. Rugged wheel is simple to repair in the field. Wheel sometimes coated with special material. Not common for HVAC applications.
Same heating, ventilating, and air-conditioning applications as airfoil fan. Used in some industrial applications where airfoil blade may corrode or erode due to environment.
General heating, ventilating, and air-conditioning applications.
Highest efficiencies occur at 50 to 60% of wide open volume. This volume also has good pressure characteristics. Power reaches maximum near peak efficiency and becomes lower, or self-limiting, toward free delivery.
Performance similar to backward-curved fan, except capacity and pressure is lower. Lower efficiency than backward-curved fan because air turns 90. Performance curve of some designs is similar to axial flow fan and dips to left of peak pressure.
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
PR
ES
SU
RE
-PO
WE
R
EFF
ICIE
NC
Y
VOLUME FLOW RATE, Q
10
108
8
6
4
2
0
6
4
2
00 2 4 6 8 10
Ps
Pt
ts
wo
Usually only applied to large systems, which may be low-, medium-, or high-pressure applications. Applied to large, clean-air industrial operations for significant energy savings.
a: These performance curves reflect general characteristics of various fans as commonly applied. They are not intended to provide complete selection criteria, since other parameters, such as diameter and speed, are not defined.
-
13
AMCA 201-02 (R2007)
5. Catalog Performance Tables
5.1 Type A: Free inlet, free outlet fans
Fans designed for use other than with duct systems
are usually rated over a lower range of pressures.
They are commonly cataloged and sold as a
complete unit with suitable drive and motor.
Typical fans in this group are propeller fans and
power roof ventilators. They are usually available in
direct or belt-drive arrangements and performance
ratings are published in a modified form of the multi-
rating table. Figure 5.1 illustrates such a table for part
of a line of belt-drive propeller fans.
5.2 Ducted fans
There are three types of ducted fans, as described in
Section 3:
1) Type B: Free inlet, ducted outlet
2) Type C: Ducted inlet, free outlet
3) Type D: Ducted inlet, ducted outlet
The performance of fans intended for use with duct
systems is usually published in the form of a "multi-
rating" table. A typical multi-rating table, as illustrated
in Figure 5.2 shows:
a) the speed (N) in rpmb) the power (H) in kw (hp)c) the fan static pressure (Ps) in Pa (in. wg)d) the outlet velocity (V) in m/s, (fpm)e) the airflow (Q) in m3/s (cfm)
Figure 5.3 shows constant speed characteristic
curves superimposed on a section of the multi-rating
table for the same fan. A brief study of this figure will
assist in understanding the relationship between
curves and the multi-rating tables.
Figure 5.1 - Propeller Fan Performance Table
SIZE
(cm)
No. of
Blades
Motor
kWrpm
Peak
kW
AIRFLOW (m3/s) @ STATIC PRESSURE (Pa)
0 31 62 93 124 155 186 217 248
61 3
0.19 862 0.13 2.02 1.58 0.58
0.19 960 0.20 2.25 1.87 0.97
0.25 1071 0.27 2.51 2.18 1.76 0.76
0.37 1220 0.40 2.86 2.57 2.24 1.70 0.81
69 3
0.19 806 0.20 2.89 2.36 1.05
0.25 883 0.27 3.17 2.68 1.94 0.76
0.37 1035 0.43 3.71 3.30 2.85 1.56 0.95
0.56 1165 0.62 4.18 3.83 3.44 3.01 1.60 1.10
84 3
0.37 825 0.42 4.36 3.76 3.04 1.27
0.56 945 0.62 4.99 4.48 3.92 2.38 1.42
0.75 1045 0.82 5.23 5.08 4.57 4.01 2.31 1.52
1.12 1190 1.19 6.29 5.90 5.47 5.01 4.48 2.79 1.94
1.49 1306 1.64 6.91 6.53 6.15 5.75 5.32 4.81 3.05 2.24 1.84
SIZE
(in.)
No. of
Blades
Motor
hprpm
Peak
bhp
AIRFLOW (ft3/min) @ STATIC PRESSURE (in. wg)
0 1/8 1/4 3/8 1/2 5/8 3/4 7/8 1
24 3
1/4 862 0.18 4,283 3,350 1,230
1/4 960 0.27 4,770 3,960 2,050
1/3 1071 0.36 5,321 4,620 3,730 1,600
1/2 1220 0.54 6,062 5,450 4,750 3,600 1,710
27 3
1/4 806 0.27 6,123 4,990 2,230
1/3 883 0.36 6,708 5,675 4,100 1,620
1/2 1035 0.57 7,862 7,000 6,035 3,315 2,020
3/4 1165 0.83 8,850 8,110 7,290 6,385 3,400 2,330
33 3
1/2 825 0.56 9,240 7,970 6,430 2,700
3/4 945 0.83 10,580 9,500 8,300 5,040 3,010
1 1045 1.1 11,710 10,755 9,685 8,490 4,890 3,215
1 1190 1.6 13,335 12,490 11,580 10,610 9,500 5,905 4,100
2 1306 2.2 14,630 13,845 13,030 12,185 11,280 10,200 6,470 4,740 3,900
TYPICAL RATING TABLE FOR A SERIES OF BELT-DRIVEN PROPELLER FANS
TYPICAL RATING TABLE FOR A SERIES OF BELT-DRIVEN PROPELLER FANS
-
Volume
CFM
Outlet
Vel.
(fpm)
1/4 in. wg 3/8 in. wg 1/2 in. wg 5/8 in. wg 3/4 in. wg 7/8 in. wg 1 in. wg 1-1/4 in. wg 1-1/2 in. wg
rpm bhp rpm bhp rpm bhp rpm bhp rpm bhp rpm bhp rpm bhp rpm bhp rpm bhp
3825
4590
5355
6120
6885
500
600
700
800
900
222
236
253
272
292
0.185
0.233
0.292
0.365
0.450
270
284
300
317
0.334
0.400
0.483
0.579
313
327
343
0.519
0.608
0.716
352
366
0.743
0.856 389 1.01 411 1.17
7650
8415
9180
9945
10710
1000
1100
1200
1300
1400
314
338
361
385
409
0.560
0.682
0.826
0.989
1.175
337
358
379
402
425
0.695
0.832
0.988
1.163
1.360
360
378
398
419
441
0.840
0.981
1.149
1.340
1.553
383
399
417
437
457
0.992
1.144
1.314
1.514
1.741
403
419
436
454
473
1.15
1.31
1.49
1.69
1.93
424
438
455
472
489
1.31
1.48
1.68
1.89
2.12
443
458
472
489
506
1.48
1.60
1.86
2.09
2.34
494
507
522
538
2.04
2.25
2.49
2.76
540
554
568
2.67
2.92
3.20
11475
12240
13005
13770
14535
1500
1600
1700
1800
1900
434
458
483
508
1.387
1.626
1.895
2.191
449
473
498
522
547
1.587
1.837
2.115
2.424
2.767
464
488
511
535
559
1.780
2.048
2.346
2.665
3.017
479
501
525
538
571
1.993
2.269
2.570
2.901
3.275
494
515
537
560
584
2.19
2.49
2.80
3.15
3.52
509
529
550
572
595
2.40
2.70
3.03
3.40
3.78
524
543
564
585
606
2.61
2.92
3.26
3.64
4.04
555
572
590
610
630
3.06
3.39
3.73
4.12
4.55
584
600
617
635
654
3.52
3.87
4.24
4.63
5.07
15300
16830
18360
19890
21420
2000
2200
2400
2600
2800
571
621
3.144
4.003
585
633
682
3.403
4.289
5.335
595
644
693
742
791
3.672
4.577
5.632
6.885
8.308
607
654
703
752
801
3.93
4.87
5.96
7.22
8.67
618
665
712
761
810
4.21
5.16
6.28
7.56
9.03
629
675
721
769
818
4.48
5.46
6.61
7.91
9.40
651
695
741
788
834
5.02
6.06
7.24
8.60
10.15
674
715
759
805
852
5.56
6.65
7.90
9.30
10.88
22950
24480
26010
27540
29070
30600
3000
3200
3400
3600
3800
4000
850 10.32 859
908
10.71
12.50
867
916
965
1015
11.09
13.01
15.16
17.52
883
932
981
1030
1072
1129
11.89
13.84
16.03
18.47
21.16
24.11
898
946
995
1044
1093
1142
12.70
14.70
16.92
19.39
22.13
25.16
IMPELLER DIAMETER: 36.5 IN OUTLET AREA: 7.65 SQ FT
TIP SPEED IN FPM: 9.56 RPM MAXIMUM BHP: 18.3 (RPM/1000)3
TYPICAL MULTISPEED RATING TABLE FOR A SINGLE WIDTH, SINGLE INLET CENTRIFUGAL FAN
Figure 5.2 - Centrifugal Fan Performance Tables
IMPELLER DIAMETER: 927 mm OUTLET AREA: .71 SQ METERS
TIP SPEED IN m/s: .0485 RPM MAXIMUM kW: 13.65 (RPM/1000)3
Volume
m3/s
Outlet
Vel.
(m/s)
62 Pa 93 Pa 124 Pa 155 Pa 186 Pa 217 Pa 246 Pa 310 Pa 373 Pa
rpm kW rpm kW rpm kW rpm kW rpm kW rpm kW rpm kW rpm kW rpm kW
1.81
2.17
2.53
2.89
3.25
2.55
3.06
3.56
4.07
4.58
222
236
253
272
292
0.14
0.17
0.22
0.27
0.34
270
284
300
317
0.25
0.30
0.36
0.43
313
327
343
0.39
0.45
0.53
352
366
0.55
0.64 389 0.75 411 0.87
3.61
3.97
4.33
4.69
5.06
5.08
5.59
6.10
6.61
7.13
314
338
361
385
409
0.42
0.51
0.62
0.74
0.88
337
358
379
402
426
0.52
0.62
0.74
0.87
1.01
360
378
398
419
441
0.63
0.73
0.86
1.00
1.16
382
399
417
437
457
0.74
0.85
0.98
1.13
1.30
403
419
436
454
473
0.86
0.98
1.11
1.26
1.44
424
438
455
472
489
0.98
1.10
1.25
1.41
1.58
443
458
472
489
506
1.10
1.19
1.39
1.56
1.74
494
507
522
538
1.52
1.68
1.86
2.06
540
554
568
1.99
2.18
2.39
5.42
5.78
6.14
6.50
6.86
7.63
8.14
8.65
9.15
9.66
434
458
483
508
1.03
1.21
1.41
1.63
449
473
498
522
547
1.18
1.37
1.58
1.81
2.06
464
488
511
535
559
1.33
1.53
1.75
1.99
2.25
479
501
525
538
571
1.49
1.69
1.92
2.16
2.44
494
515
537
560
584
1.63
1.86
2.09
2.35
2.62
509
529
550
572
595
1.79
2.01
2.26
2.54
2.82
524
543
564
585
606
1.95
2.18
2.43
2.71
3.01
555
572
590
610
630
2.28
2.53
2.78
3.07
3.39
584
600
617
635
654
2.62
2.89
3.16
3.45
3.78
7.22
7.94
8.67
9.39
10.11
10.17
11.18
12.21
13.23
14.24
571
621
2.34
2.99
585
633
682
2.54
3.20
3.98
595
644
693
742
791
2.74
3.41
4.20
5.13
6.20
607
654
703
752
801
2.93
3.63
4.44
5.38
6.47
616
665
712
761
810
3.14
3.85
4.68
5.64
6.73
629
675
721
769
818
3.34
4.07
4.93
5.90
7.01
651
695
741
788
834
3.74
4.52
5.40
6.41
7.57
674
715
759
805
852
4.15
4.96
5.89
6.94
8.11
10.83
11.55
12.28
13.00
13.72
14.44
15.25
16.27
17.30
18.31
19.32
20.34
850 7.70 859
908
7.99
9.40
867
916
965
1015
8.27
9.70
11.30
13.06
883
932
981
1030
1072
1129
8.87
10.32
11.95
13.77
15.78
17.98
898
946
995
1044
1093
1142
9.47
10.96
12.62
14.46
16.50
18.76
TYPICAL MULTISPEED RATING TABLE FOR A SINGLE WIDTH, SINGLE INLET CENTRIFUGAL FAN
AMCA 201-02 (R2007)
14
-
222
236
253
272
292
.185
.233
.292
.365
.450
270
284
300
317
.334
.400
.483
.579
313
327
343
.51
9.6
08
.71
6352
366
.743
.856
389
1.0
1411
1.1
7
314
338
361
335
409
.560
.682
.826
.988
1.1
75
337
358
379
482
426
.695
.822
.988
1.1
63
1.3
60
360
378
398
419
441
.84
0.9
81
1.1
49
1.3
40
1.5
53
332
399
417
437
457
.992
1.1
44
1.3
14
1.5
14
1.7
41
403
419
436
454
473
1.1
51.3
11.4
91.6
91.9
3
424
438
455
472
489
1.3
11.4
81.5
81.8
92.1
2
443
458
472
489
506
1.4
81.6
01.8
62.0
92.3
4
494
507
522
538
2.0
42.2
52.4
92.7
6
540
554
568
2.6
72.9
23.2
8584
598
3.3
73.6
6
434
456
482
508
1.3
87
1.6
26
2.1
9
449
473
493
522
547
1.5
87
1.8
37
2.1
15
2.4
24
2.7
67
464
488
511
535
559
1.7
82.0
48
2.3
46
2.6
65
3.0
17
479
501
525
538
571
1.9
95
2.2
69
2.5
70
2.9
01
3.2
76
494
515
537
560
584
2.1
92.4
92.8
03.1
53.5
2
509
529
550
572
595
2.4
02.7
03.0
33.4
0
524
543
564
585
606
2.6
12.9
23.2
63.8
44.0
4
555
572
590
610
630
3.0
63.4
93.7
34.1
24.5
5
584
600
617
635
654
3.5
23.8
74.2
44.6
35.0
7
612
627
643
661
678
3.9
94.3
64.7
65.1
85.6
3
571
629
3.7
44
4.0
03
584
633
682
3.4
03
4.2
89
5.3
35
596
644
693
742
791
4.5
77
5.6
32
6.8
85
8.3
08
607
654
703
752
801
3.9
34.8
75.7
67.2
28.6
7
618
665
712
761
810
4.2
15.1
66.2
87.5
69.0
3
629
675
721
769
818
4.4
85.4
66.8
17.9
18.4
8
651
695
741
788
834
5.0
26.0
67.2
48.6
010.1
5
674
715
759
852
5.5
66.6
57.9
09.3
010.8
8
696
736
778
822
867
6.1
17.2
4
10.0
211
.65
850
10.3
2859
908
10.7
112.6
0867
916
965
10
15
11.0
913.0
115.1
617.5
2
883
932
981
1030
1079
1129
11.8
913.8
416.0
318.4
721.1
624.1
1
898
946
995
1044
1093
1142
12.7
014.7
016.9
219.3
922.1
325.1
6
914
960
10
09
1057
1106
1155
13.4
815.5
617.8
320.3
523.1
226.1
8
RECOMMENDEDSELECTION RANGE810 RPM585 RPM
490 RPM
390 RPM
PR
ES
SU
RE
IN IN
. WG
BR
AK
E H
OR
SE
PO
WE
R
VO
LUM
EC
FMO
UTL
ET
VE
LOC
ITY
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
3825
4590
5355
6120
6885
7650
8415
9180
9945
1071
0
1147
512
240
1300
513
770
1453
5
1530
016
830
1836
019
890
2142
0
2295
024
480
2601
027
540
2907
030
600
CFM
1/4
SP
3/8
SP
1/2
SP
5/8
SP
3/4
SP
7/8
SP
1 S
P1-
1/4
SP
1-1/
2 S
P1-
3/4
SP
RP
MB
HP
RP
MB
HP
RP
MB
HP
RP
MB
HP
RP
MB
HP
RP
MB
HP
RP
MB
HP
RP
MB
HP
RP
MB
HP
RP
MB
HP
AMCA 201-02 (R2007)
15
Figure 5.3 - Typical Fan Performance Table Showing Relationship to a Family
of Constant Speed Performance Curves
-
Most performance tables do not cover the complete
range from no delivery to free delivery but cover only
the typical operating range. Figure 5.4 illustrates the
recommended performance range of a centrifugal
fan. Comparison of Figure 5.4 with Figure 5.3 will
show that the published performance table also
covers only the recommended performance range of
the fan.
It should be remembered that fans are generally
tested without obstructions in the inlet and outlet and
without any optional airstream accessories in place.
Catalog ratings will, therefore, usually apply only to
the bare fan with unobstructed inlet and outlet.
Fan performance adjustment factors for airstream
accessories are normally available from either the fan
catalog or the fan manufacturer.
Fans are usually tested in arrangement 1, or similar
(see Figure 3.5). Rating tables will, therefore, also
apply only to the tested arrangement. Allowances for
the effect of bearing supports used in other
arrangements should be obtained from the
manufacturer if not shown in the catalog.
6. Air Systems
6.1 The system
An air system may consist simply of a fan with
ducting connected to either the inlet or outlet or to
both. A more complicated system may include a fan,
ductwork, air control dampers, cooling coils, heating
coils, filters, diffusers, sound attenuation, turning
vanes, etc. See AMCA Publication 200 Air Systems,for more information.
6.2 Component losses
Every system has a combined resistance to airflow
that is usually different from every other system and
is dependent upon the individual components in the
system.
The determination of the "pressure loss" or
"resistance to airflow," for the individual components
can be obtained from the component manufacturers.
The determination of pressure losses for ductwork
design is well documented in standard handbooks
such as the ASHRAE Handbook of Fundamentals.
AIRFLOW
PR
ES
SU
RE
SELECTION NOT USUALLY
RECOMMENDED IN THIS RANGE
SELECTION
NOT USUALLY
RECOMMENDED
IN THIS RANGE
RECOMMENDED
SELECTION RANGE
PR
ESSU
RE
DUCT
SYST
EM C
URVE
DU
CT S
YSTEM
CU
RVE
Figure 5.4 - Recommended Performance Range of a Typical Centrifugal Fan
AMCA 201-02 (R2007)
16
-
In a later section, the effects of some system
components and fan accessories on fan performance
are discussed. The System Effects presented willassist the system designer to determine fan
selection.
6.3 The system curve
At a fixed airflow through a given air system a
corresponding pressure loss, or resistance to this
airflow, will exist. If the airflow is changed, the
resulting pressure loss, or resistance to airflow, will
also change. The relationship between airflow
pressure and loss can vary as a function of type of
duct components, their interaction and the local
velocity magnitude. In many cases, typical duct
systems operate in the turbulent flow regime and the
pressure loss can be approximated as a function of
velocity (or airflow) squared. The simplifying
relationship used in this publication governing the
change in pressure loss as a function of airflow for a
fixed system is:
Pc/P = (Qc/Q)2
A more through discussion of duct system pressure
losses can be found in AMCA Publication 200 AirSystems.
The system curve of a "fixed system" plots as a
parabola in accordance with the above relationship.
Typical plots of the resistance to flow versus volume
airflow for three different and arbitrary fixed systems,
(A, B, and C) are illustrated in Figure 6.1. For a fixed
system an increase or decrease in airflow results in
an increase or decrease in the system resistance
along the given system curve only. Also, as the
components in a system change, the system curve
changes.
Refer to Figure 6.1, Duct System A. With a system at
the design airflow (Q) and at a design systemresistance (P), an increase in airflow to 120% of Qwill result in an increase in system resistance P of144% since system resistance varies with the square
of the airflow. Likewise, a decrease in airflow Q to50% would result in a decrease in system resistance
P to 25% of the design system resistance.
In Figure 6.1, System Curve B is representative of a
system that has more component pressure loss than
System Curve A, and System Curve C has less
component pressure loss than System Curve A.
Notice that on a percentage basis, the same
relationships also hold for System Curves B and C.
These relationships are characteristic of typical fixed
systems.
SYSTE
M B
SYST
EM A
SYST
EM C
PE
RC
EN
T O
F S
YS
TE
M R
ES
ISTA
NC
E
PERCENT OF SYSTEM AIRFLOW
0
20
40
60
80
100
120
140
160
180
200
0
20 40 60 80 100 120 140 160 180 200
SYSTEMDESIGN POINT
Figure 6.1 - System Curves
AMCA 201-02 (R2007)
17
-
6.4 Interaction of system curve and fan
performance curve
If the system characteristic curve, composed of the
resistance to system airflow and the appropriate SEFhave been accurately determined, then the fan will
deliver the designated airflow when installed in the
system.
The point of intersection of the system curve and the
fan performance curve determines the actual airflow.
System Curve A in Figure 6.2 has been plotted with a
fan performance curve that intersects the system
design point.
The airflow through the system in a given installation
may be varied by changing the system resistance.
This is usually accomplished by using fan dampers,
duct dampers, mixing boxes, terminal units, etc.
Figure 6.2 shows the airflow may be reduced from
design Q by increasing the resistance to airflow, i.e.,changing the system curve from System A to System
B. The new operating point is now at Point 2 (the
intersection of the fan curve and the new System B)
with the airflow at approximately 80% of Q. Similarly,the airflow can be increased by decreasing the
resistance to airflow, i.e., changing the system curve
from System A to System C. The new operating point
is now at Point 3 (the intersection of the fan curve and
the new System C), with the airflow at approximately
120% of Q.
6.5 Effect of changes in speed
Increases or decreases in fan rotational speed will
alter the airflow through a system. According to the
Fan Laws (see below), the % increase in airflow is
directly proportional to the fan rotational speed ratio,
and the fan static pressure is proportional to the
square of the fan rotational speed ratio. Thus, a 10%
increase in fan rotational speed will result in a new
fan curve with a 10% increase in Q, as illustrated inFigure 6.3. Since the system components did not
change, System Curve A remains the same. With
airflow increasing by 10% over the original Q, thesystem resistance increases along System Curve A
to Point 2, at the intersection with the new fan curve.
The greater airflow moved by the fan against the
resulting higher system resistance to airflow is a
measure of the increased work done. In the same
system, the fan efficiency remains the same at all
points on the same system curve.
This is due to the fact that airflow, system resistance,
and required power are varied by the appropriate
ratio of the fan rotational speed.
200
0
20
40
60
80
100
120
140
160
180
200
40 60 80 100 120 140 160 180 200
FAN CURVE
SYST
EM B
SY
STE
M A
SYST
EM C
SYSTEMDESIGN POINT
1
2
3
PERCENT OF SYSTEM AIRFLOW
PE
RC
EN
T O
F S
YS
TE
M R
ES
ISTA
NC
E
Figure 6.2 - Interaction of System Curves and Fan Curve
AMCA 201-02 (R2007)
18
-
PERCENT OF SYSTEM AIRFLOW
PE
RC
EN
T O
F P
OW
ER
PE
RC
EN
T O
F S
YS
TE
M R
ES
ISTA
NC
E
0
0
20
40
60
80
100
120
140
160
20 40 60 80 100
100
133
50
120 140
110%
160 180 200
H (AT 1.1N)PRESSURE
S (AT 1.1N) DU
CT S
YS
TE
M A
PRESSURES (AT N)
H (AT N)1
2
Figure 6.3 - Effect of 10% increase in Fan Speed
AMCA 201-02 (R2007)
6.5.1 Fan Laws - effect of change in speed - (fan
size and air density remaining constant)
For the same size fan, Dc = D and, therefore, (Dc/D)= 1. When the air density does not vary, c = andthe air density ratio (c/) = 1. Kp is taken as equal tounity in this and following examples.
Qc = Q (Nc/N)
Ptc = Pt (Nc/N)2
Psc = Ps (Nc/N)2
Pvc = Pv (Nc/N)2
Hc = H (Nc/N)3
6.6 Effect of density on system resistance
The resistance of a duct system is dependent upon
the density of the air flowing through the system. An
air density of 1.2 kg/m3 (0.075 lbm/ft3) is standard in
the fan industry throughout the world. Figure 6.4
illustrates the effect on the fan performance of a
density variation from the standard value.
6.6.1 Fan Laws - effect of change in density - (fan
size and speed remaining constant)
When the speed of the fan does not change, Nc = Nand, therefore, (Nc/N) = 1. The fan size is also fixed,Dc = D and therefore (Dc/D) = 1.
Qc = Q
Ptc = Pt (c/)
Psc = Ps (c/)
Pvc = Pv (c/)
Hc = H (c/)
19
-
00
0 20 40 60 80 100 120 140 160 180 200
20
40
60
80
100
20
40
60
80
100
PERCENT OF SYSTEM AIRFLOW
PE
RC
EN
T O
F P
OW
ER
PE
RC
EN
T O
F S
YS
TE
MR
ES
ISTA
NC
E A
ND
FA
N P
RE
SS
UR
E
POWER @ DENSITY
FAN PRESSURE CURVE@ DENSITY /2
FAN PRESSURE CURVE@ DENSITY SYSTEM A
@ DENSITY FAN INLET
SYSTEM A@ DENSITY /2
FAN INLET
POWER @ DENSITY /2
Figure 6.4 - Density Effect
AMCA 201-02 (R2007)
20
-
CALCULATED SYSTEM CURVE
PEAK FAN PRESSURE
FAN PRESSURE
CURVE
DESIGN AIRFLOW
DE
SIG
N R
ES
ISTA
NC
E
1
Figure 6.5 - Fan/System Curve at Design Point
AMCA 201-02 (R2007)
6.7 Fan and system interaction
When system pressure losses have been accurately
estimated and desirable fan inlet and outlet
conditions have been provided, design airflow can be
expected, as illustrated in Figure 6.5. Note again that
the intersection of the actual system curve and the
fan curve determine the actual airflow. However,
when system pressure losses have not been
accurately estimated as in Figure 6.6, or when
undesirable fan inlet and outlet conditions exist as in
Figure 6.7, design performance may not be obtained.
6.8 Effects of errors in estimating system
resistance
6.8.1 Higher system resistance. In Figure 6.6,
System Curve B shows a situation where a system
has greater resistance to airflow than designed
(Curve A). This condition is generally a result of
inaccurate allowances of system resistance. All
pressure losses must be considered when
calculating system resistance or the actual system
will be more restrictive to airflow than intended. This
condition results in an actual airflow at Point 2, which
is at a higher pressure and lower airflow than was
expected.
If the actual duct system pressure loss is greater than
design, an increase in fan speed may be necessary
to achieve Point 5, the design airflow.
CAUTION: Before increasing fan rotational
speed, check with the fan manufacturer to
determine whether the fan rotational speed can
be safely increased. Also determine the expected
increase in power. Since the power required
increases as the cube of the fan rotational speed
ratio, it is very easy to exceed the capacity of the
existing motor and that of the available electrical
service.
6.8.2 Lower system resistance. Curve C in Figure
6.6 shows a system that has less resistance to airflow
than designed. This condition results in an actual
airflow at Point 3, which is at a lower pressure and
higher airflow than was expected.
21
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FAN PRESSURECURVE
CURVE B:ACTUAL SYSTEM
CURVE A:CALCULATED SYSTEM
CURVE CACTUAL SYSTEM
PEAK FANPRESSURE
ACTUAL SYSTEM RESISTANCEMORE THAN DESIGN
ACTUAL SYSTEMLESS THANDESIGN
DESIGN AIRFLOW
DE
SIG
N R
ES
ISTA
NC
E
5
1
2
4
3
Figure 6.6 - Fan/System Curve Not at Design Point
AMCA 201-02 (R2007)
6.9 Safety factors
It has been common practice among system
designers to add safety factors to the calculated
system resistance to account for the unexpected.
In some cases, safety factors may compensate for
resistance losses that were unaccounted for and the
actual system will deliver the design airflow, Point 1,
Figure 6.6. If the actual system resistance is lower
than the design system resistance, including the
safety factors, the fan will run at Point 3 and deliver
more airflow. This result may not be advantageous
because the fan may be operating at a less efficient
point on the fans performance curve and may require
more power than a properly designed system. Under
these conditions, it may be desirable to reduce the
fan performance to operate at Point 4 on Curve C,
Figure 6.6. This may be accomplished by reducing
the fan speed, adjusting the variable inlet vane (VIV),
if installed, or inlet dampers. The system resistance
could also be increased to Point 1 on Curve A, Figure
6.6. The change in fan operating point should be
evaluated carefully, since a change in fan power
consumption may occur.
The system designer should also evaluate the fan
performance tolerance and system resistance
tolerance to determine if the lower or upper limits of
the probable airflow in the system are acceptable.
The combination of these tolerances should be
evaluated to ensure that the high-side system
resistance curve does not fall into the unstable range
of performance. Operation in this area of the curve
should be avoided and precautions taken to ensure
operations outside of the unstable area, especially at
the highest expected system resistance.
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AMCA 201-02 (R2007)
6.10 Deficient fan/system performance
The most common causes of deficient fan/system
performance are improper fan inlet duct design, fan
outlet duct design, and fan installation into the duct
system. Any one or a combination of these conditions
that alter the aerodynamic characteristics of the air
flowing through the fan such that the fans full airflow
potential, as tested in the laboratory and cataloged, is
not likely to be realized.
Other major causes of deficient performance are:
The air performance characteristics of the
installed system are significantly different from
the system designer's intent (See Figure 6.6).
This may be due to a change in the system by
others or unexpected behavior of the system
during operation.
The system design calculations did not include
adequate allowances for the effect of accessories
and appurtenances (See Section 10).
The fan selection was made without allowing
for the effect of appurtenances on the fan's
performance (See Section 10).
Dirty filters, dirty ducts, dirty coils, etc., will
increase the system resistance, and
consequently, reduce the airflow - often
significantly.
The "performance" of the system has been
determined by field measurement techniques
that have a high degree of uncertainty.
Other "on-site" problems are listed in AMCA
Publication 202 Troubleshooting, which includesdetailed checklists and recommendations for the
correction of problems with the performance of air
systems.
6.11 Precautions to prevent deficient
performance
Use appropriate allowances in the design
calculations when space or other factors
dictate the use of less than optimum
arrangement of the fan outlet and inlet
connections (See Sections 8 and 9).
Design the connections between the fan and
the system to provide, as nearly as possible,
uniform airflow conditions at the fan outlet and
inlet connections (See Sections 8 and 9).
Include adequate allowance for the effect of all
accessories and appurtenances on the
performance of the system and the fan. If
possible, obtain from the fan manufacturer
data on the effect of installed appurtenances
on the fan's performance (See Section 10).
Use field measurement techniques that can be
applied effectively on the particular system.
Be aware of the probable accuracy of
measurement and conditions that affect this.
Refer to AMCA Publication 203 FieldPerformance Measurement of Fan Systems;for more precise measurement see AMCA
Standard 803 Industrial Process/PowerGeneration Fans: Site Performance TestStandard. Also, refer to AABC NationalStandards, Chapter 8, Volume Measurements,
Associated Air Balance Council, 5th Edition,
1989.
6.12 System Effect
Figure 6.7 illustrates deficient fan/system
performance resulting from one or more of the
undesirable airflow conditions listed in Section 6.10.
It is assumed that the system pressure losses, shown
in system curve A, have been accurately determined,
and a suitable fan selected for operation at Point 1.
However, no allowance has been made for the effect
of the system connections on the fan's performance.
To account for this System Effect it will be necessary
to add a System Effect Factor (SEF) to the calculatedsystem pressure losses to determine the actual
system curve. The SEF for any given configuration isvelocity dependent and will vary across a range of
airflow. This will be discussed in more detail in
Section 7. (See Figure 7.1).
In Figure 6.7 the point of intersection between the fan
performance curve and the actual system curve B is
Point 4. The actual airflow will be deficient by the
difference 1-4. To achieve design airflow, a SEFequal to the pressure difference between Point 1 and
2 should have been added to the calculated system
pressure losses and the fan selected to operate at
Point 2. Note that because the System Effect is
velocity related, the difference represented between
Points 1 and 2 is greater than the difference between
Points 3 and 4.
The System Effect includes only the effect of the
system configuration on the fan's performance.
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AMCA 201-02 (R2007)
7. System Effect Factor (SEF)
A System Effect Factor is a value that accounts forthe effect of conditions adversely influencing fan
performance when installed in the air system.
7.1 System Effect Curves
Figure 7.1 shows a series of 19 System Effect
Curves. By entering the chart at the appropriate air
velocity (on the abscissa), it is possible to read
across from any curve (to the ordinate) to find the
SEF for a partic