amca publication 201-02 (r2007)

The International Authority on Air System Components

AIR MOVEMENT AND CONTROLASSOCIATION INTERNATIONAL, INC.

AMCAPublication 201-02

Fans and Systems

(R2007)

AMCA PUBLICATION 201-02 (R2007)

Fans and Systems

Air Movement and Control Association International, Inc.

30 West University Drive

Arlington Heights, IL 60004-1893

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.

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

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.

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

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

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

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

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

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

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)


Impeller mounted on shaft

between bearings supported by

the fan casing.


on independent pedestals, with


3 DWDI 6 or

18 (Arr. 6 with

sub-base)



between bearings supported by

the fan casing.


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.





Motor flange mounted to

casing.


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



AMCA Drive

Arrangement

ISO 13349

Drive

Arrangement


Configuration

7 SWSI 7 For coupling drive.

Generally the same as Arr. 3,

with base for the prime mover.


on independent pedestals with


7DWDI 17

(Arr. 6 with

base for motor)

For coupling drive.

Generally the same as Arr. 3











9 SWSI 9 For belt drive.


bearings mounted on pedestal

base.

Motor mounted on the outside

of the bearing base.


10 SWSI 10 For belt drive.


with motor mounted inside of

the bearing pedestal.



AMCA 201-02 AMCA 201-02 (R2007)

7



Drive Arrangements for Axial FansAn American National Standard - Approved by ANSI on June 10, 2003

AMCA Drive

Arrangement

ISO 13349

Drive

Arrangement


Configuration

1 1

12 (Arr. 1 with

sub-base)



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)



between bearings on internal

supports.

Alternative: Fan can be

supplied with inlet box, and/or

discharge evas.

4 4 For direct drive.



Motor mounted on base or

integrally mounted.

Alternative: With inlet box

and/or with discharge evas.

M MM M





and/or discharge evas.

M M




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.


and/or discharge evas

M

Note: All fan orientations may be horizontal or vertical


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


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


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


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

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.

22

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.

23

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

amca publication 201-02 (r2007)

Documents

amca international standards

amca standards

performance of fans

international authority

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duct system designcan

duct system configurations

duct system design effect