System Effects Presented by: Joe Brooks, AMCA International, Inc. AMCA International Technical Seminar 2009

System Effects, Slide 2 The Air Movement and Control Association International (AMCA), has met the standards and requirements of the Registered Continuing Education Providers Program. Credit earned on completion of this program will be reported to the RCEPP. A certificate of completion will be issued to each participant. As such, it does not include content that may be deemed or construed to be an approval or endorsement by NCEES or RCEPP.

System Effects, Slide 3 Learning Objectives Describe system resistance of components Describe system resistance of components Know how a fan interacts with the system Know how a fan interacts with the system Define System Effect and System Effect Factor (SEF) Define System Effect and System Effect Factor (SEF) Know how to avoid system effect factors Know how to avoid system effect factors

System Effects, Slide 4 Two Components of System Design Calculate flow resistance losses for each component in the system Select and position fan to avoid system effect loss  If loss cannot be avoided, estimate loss and select fan for higher pressure

System Effects, Slide 5 Ductwork Example System Resistance System Effect Controlled by Inlet and Outlet Conditions

System Effects, Slide 6 Causes of Non-Performing Systems System resistance miscalculated. Fan not properly selected. Defective fan (or fan rating). There is a system effect loss.

System Effects, Slide 7 Fan Manufacturer’s Responsibility Provide accurate fan performance ratings. Provide a fan built within tolerance so that it is capable of meeting its rating.

System Effects, Slide 8 What is System Effect? A factor used to correct for system induced installation effects. The difference in performance between a fan tested in the laboratory and one tested in a real installation.

System Effects, Slide 9 Inlet Connections ASHRAE Guidelines

System Effects, Slide 10 Outlet Connections ASHRAE Guidelines

System Effects, Slide 11 Outlet Connections ASHRAE Guidelines

System Effects, Slide 12 What is Missing? Only guidelines to avoid losses. No way to quantify losses.

System Effects, Slide 13 AMCA Publication The bible of system effects Generated from ASHRAE funded research

System Effects, Slide 14 Credibility Gap Are system effects just fudge factors that the fan manufacturers made up? System effect video.

System Effects, Slide 15 Definition of System Effect Fan ratings are established using AMCA 210 test codes that are close to ideal conditions. Fans in actual systems are often less than ideal. The difference in performance for the same fan tested in both conditions is the “System Effect”.

System Effects, Slide 16 Purpose of Discussion Aimed primarily at the fan system designer There are two goals: Avoid poor fan system configurations When optimum conditions cannot be met, use the “system effect” factors to estimate any losses during system design.

System Effects, Slide 17 Why System Effect is Important May have to accept deficient performance, or...  Speed up the fan (if possible)  May require more energy to meet performance  May exceed motor horsepower limit Many cause excessive noise Many cause excessive vibration

System Effects, Slide 18 Normal System Performance Design volume Fan curve Calculated duct system curve 1

System Effects, Slide 19 Deficient Performance With System Effect Design volume Original fan curve Deficient volume 3 Calculated duct system with no allowance for system effect 4 System effect at actual flow volume 1 Operating point is at point 3  Operating point is not on fan curve!

System Effects, Slide 20 Correcting For System Effect Design volume Original fan curve New fan curve System effect loss at design volume 2 Deficient volume 3 Calculated duct system with no allowance for system effect 4 System effect at actual flow volume Actual duct system with system effect 1

System Effects, Slide 21 The fan will be selected for the higher pressure (no need to speed up). The motor will be selected to include the anticipated loss. With System Effects Added:

System Effects, Slide 22 What are the Causes of the Losses? Inlet losses are caused by:  Unequal loading of the fan blades (eccentric flow).  Improper fan blade attack angle.  Turbulence which disrupts the flow. Outlet losses are caused by:  Loss of conversion of local high velocity into pressure.

System Effects, Slide 23 Inlet induced losses tend to be higher than outlet losses. Losses induced on the inlet can often exceed 20%. Losses as high as 50% have been reported. Inlet vs. Outlet Losses

System Effects, Slide 24 Straight uniform flow directed only in the axial direction--on the fan inlet For Ducted fans - a straight length of outlet ductwork Good Flow Conditions for a Fan:

System Effects, Slide 26 AMCA Publication Defines standard methods of testing fans for rating purposes

System Effects, Slide 27 How are the Losses Quantified? AMCA 201 publishes data for a variety of configurations Most identify a “Loss Curve” which is based on the configuration and identified by a letter  Most also need the air velocity as a parameter.

System Effects, Slide 28 System Effect Curves 4000 FPM Curve T Add 0.55 to Static Pressure

System Effects, Slide 29 Outlet System Effects In addition to the flow velocity, may need to know:  effective duct length  blast area

System Effects, Slide 30 System Effect Curves for Outlet Ducts - Axial Fans

System Effects, Slide 31 Fan Outlet Velocity Profile - Centrifugal

System Effects, Slide 32 System Effect Curves for Outlet Ducts - Centrifugal Fans

System Effects, Slide 33 Outlet Duct Elbows - Centrifugal Fans BAD WORSE

System Effects, Slide 34 S. E. Curves for Outlet Elbows on Centrif.

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System Effects, Slide 36 S. E. Curves for Outlet Elbows - Axial

System Effects, Slide 37 S. E. Curves for Inlet Elbows - Axial

System Effects, Slide 38 Percentage of Unobstructed Inlet Area

System Effects, Slide 39 Fans and Plenum – Two Losses Distance L / (Inlet Dia.) gives one loss Loss factors given for 0.3 to 0.75 clearance Note: Spacing for two fans is important Keep inlet centerline on centerline of unit No loss factors given

System Effects, Slide 40 Elbows Change the Velocity Profile Fan inlet here will create a system effect loss for any type of fan

System Effects, Slide 41 Right Angle Turns At Fan Inlet Inlet with rectangular inlet Duct (POOR) Inlet with 3-piece elbow Inlet with special designed inlet box All methods will induce some system effect loss. Some methods are better than others

System Effects, Slide 42 System Effect - Round Inlet Ducts 2 piece mitered round section 3 piece mitered round section 4 or more piece mitered round section

System Effects, Slide 43 Forced Inlet Vortex (Inlet Spin or Swirl) Pre-Rotating Inlet Swirl Counter-Rotating Inlet Swirl

System Effects, Slide 44 Corrections for Inlet Spin

System Effects, Slide 46 Normalized Pressure-Volume Curve Note that this is similar to a variable system effect. A new curve is generated at each vane setting

System Effects, Slide 47 Pressure Drop Multipliers for Volume Control Dampers on a Fan Outlet

System Effects, Slide 48 Measured Inlet Sound Power Blade Pass Hz Vaneaxial Fan System Effect

System Effects, Slide 49 System Effect Factors are Real When designing your fan/system, do everything possible to avoid a “system effect” for efficient use of energy When conditions leading to system effect cannot be avoided, add the calculated loss to the fan pressure requirement at the system design stage.

System Effects, Slide 50 Thumb Rules Minimum of 2-1/2 Duct Diameters on Outlet, Minimum 3 to 5 Duct Diameters on Inlet, and Avoid Inlet Swirl

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System Effects, Slide 59 Questions?

System Effects, Slide 60