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Copyright © Carrier Corp. 2005
Technical Development Program 2017
Carlos MartinezRegional Sales Manager
COMMERCIAL HVAC DIVISION
Copyright © Carrier Corp. 2005
History of Innovation and Education
www.williscarrier.com
www.siglers.com/about//
Copyright © Carrier Corp. 2005
Sigler Presenters
Omar Rojas Ray Chow, P.E. Joseph MoralesUniversity of Notre Dame University of Wisconsin – Madison University of California - San Diego
Jed de la Cruz Rod Valdez Colby FischerUniversity of California-Riverside University of Illinois at Urbana–Champaign Cal Poly Pomona
Copyright © Carrier Corp. 2005
Carrier PresentersMichael Ho, PE, LEED APCarrier Corp.Business Development/ Engr. ManagerKansas State University
Stephanie Kadow- LEED APCarrier VRF DivisionCommercial Sales ManagerSan Diego State University
Copyright © Carrier Corp. 2005
Schedule
Copyright © Carrier Corp. 2005
Housekeeping Items• Download presentations on Sigler Commercial
Website siglercommercial.com > Library > TDP
• Communicate with your monitor any particularrequests, questions or concerns.
• Enjoy and send feedback to:
Carlos Martinez
Section 1 – Introduction
Copyright © Carrier Corp. 2005
COMMERCIAL HVAC EQUIPMENTFans in Variable
Air VolumeSystems
PRESENTED BY:
Michael Ho
Technical Development Program
Version 1.2
Copyright © Carrier Corp. 2005
MenuSection 1 Introduction
Section 2 Fan Impact
Section 3 Fan Types Used in VAV Systems
Section 6 Fan Volume Control
Section 7 Fan Stability
Section 8 VFD Energy Savings in VAV Systems
Section 9 VAV Fan Control Trackingand Pressurization
Section 10 Summary
Section 4 Centrifugal Fans
Section 5 Axial Fans
Copyright © Carrier Corp. 2005
SECTION 1
Introduction
FANS IN VARIABLE
AIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
Objectives• Understand the impact of fan regulation
• Identify the types of fans used in VAV
• Discuss previous and current methods offan volume control
• Utilize fan curves to demonstrate stablefan selections
• Compare fan volume control methods forenergy savings
• Discuss fan static pressure control,tracking, and pressurization
Section 1 – Introduction
Copyright © Carrier Corp. 2005
Variable Air Volume (VAV) System
SystemComponents:1. VAV Box with
Heating Coil2. Zone Thermostat3. Supply Diffuser4. Return Grille5. Duct Static
Pressure Sensor6. Supply Fan VFD7. Air Handler8. Supply Duct
Zone 1 Zone 2 Zone 3 Zone 4
Section 1 – Introduction
Copyright © Carrier Corp. 2005
SECTION 2
Fan Impact
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
Impact of Riding the Fan Curve
Designsp
Designcfmcfm
Stat
icPr
essu
re
ED
CB
A
B1
D1C1
E1
Possible Problems• Excessive duct pressure
• Excessive duct leakage
• Excessive sound levels
• Erratic VAV terminal control
• Little or no energy savings
• Possible fan instability
Forward-Curved Fan
Section 2 – Fan Impact
Copyright © Carrier Corp. 2005
SECTION 3
Fan Types Used in VAV Systems
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
Centrifugal FansAir is discharged at a right angle to fan shaft
Scroll or Fan Housing
Section 3 – Fan Types Used in VAV Systems
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Plenum FansSingle-width, single-inlet airfoil impeller design,
for mounting inside a cabinet
Section 3 – Fan Types Used in VAV Systems
Copyright © Carrier Corp. 2005
Axial (In-Line) FansAir is discharged parallel to the fan shaft
Section 3 – Fan Types Used in VAV Systems
Copyright © Carrier Corp. 2005
SECTION 4
Centrifugal Fans
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
Centrifugal Fan Construction and TerminologyBlast Area Outlet
Discharge
ImpellerWheel
RimShroudWheel RingWheel ConeInlet RimWheel Rim
Inlet CollarInlet SleeveInlet Band
BearingSupport
InletInlet ConeInlet BellInlet FlareInlet NozzleVenturi
Blades
BackplateHub DiskHubplateWebplate
Double-WidthDouble-Inlet Wheel(DWDI)
Outlet Areafor DuctConnection
Housingor Scroll
HousingSide Sheet
Section 4 – Centrifugal Fans
Copyright © Carrier Corp. 2005
Forward-Curved Wheel Design
Characteristics:• Most commonly used wheel in HVAC• Light weight – low cost• Operates at static pressures up to 5 in. wg max• 24 to 64 blades• Low rpm (800 to 1200 rpm)
Rotation
Tip
Heel
Section 4 – Centrifugal Fans
Copyright © Carrier Corp. 2005
• Overloading type fan– Horsepower will continue to
rise with increased cfm andcan overload the motor
Forward-Curved Centrifugal Fan CharacteristicsS
tatic
Pre
ssur
e
cfm
TypicalForward-Curvedrpm Line
Fan Horsepower
Dip
Section 4 – Centrifugal Fans
Copyright © Carrier Corp. 2005
Characteristics:• Blades are curved away from direction of rotation• Static pressure up to 10 in. wg• 8 to 18 blades• High rpm (1500 to 3000 rpm)
Airfoil Wheel Design
Rotation
Section 4 – Centrifugal Fans
Copyright © Carrier Corp. 2005
Airfoil Centrifugal Fan Characteristics
• Non-overloading– Horsepower will peak and
begin to drop off
Typical Airfoil rpmLine
Fan Horsepower
Sta
ticP
ress
ure
cfm
Section 4 – Centrifugal Fans
Copyright © Carrier Corp. 2005
Characteristics:• Single-Width, Single-Inlet (SWSI)• Operate at static pressures up to 10 in. wg• Best application with limited space or
when multiple duct discharge is desired
Fan WheelGuard
Inlet Cone
Plenum Fan Characteristics
Plenum fans without cabinets
Section 4 – Centrifugal Fans
Copyright © Carrier Corp. 2005
Plenum Fans With CabinetsInlet Cone SWSI Plenum Fan Wheel
Fan Cabinet
Section 4 – Centrifugal Fans
Copyright © Carrier Corp. 2005
SECTION 5
Axial Fans
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
• Use for high cfm applications
• In-line space savers with no cabinet
• Often used in industrial AC and ventilation applications
• Impeller similar to prop fans but blades are more aerodynamic
• Often used for return fans in AC applications
Axial (In-Line) Fans
PropellerType Impeller
Section 5 – Axial Fans
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Axial Impeller Design
• Axial Wheel– Air discharged parallel to the shaft– Air is often redirected via straightening
vanes making the fan a vane axial
Section 5 – Axial Fans
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SECTION 6
Fan Volume Control
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
Fan Volume Control Methods• Controllable Pitch Axial Fan
• Modudrive®
• Discharge Damper
• System Bypass
• “Riding the Fan Curve”– No Volume Control
• Inlet Guide Vanes (IGV)
• Variable Frequency Drive (VFD)
• Eddy Current Coupling
Section 6 – Fan Volume Control
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Controllable Pitch Axial Fan
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Modudrive®
• Airfoil orforward-curved fans
• Airflow modulationcontrolled by pulleyadjustment
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Discharge Damper Installation
Forward-Curved Fan
Dampers are typically mounted close to or right off the fan discharge.
Remote DuctStatic Pressure
Sensor
DischargeDamper
SP
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Discharge Damper Characteristics
Legend- rpm - bhp MSE - Max Static Eff. SC -System Curve RP - Rated Point = 15,000
rpm = 1010 bhp = 17.8 Class II Max. rpm = 1217rpms (*100, L to R): 3 4 5 6 7 8 9 10 11 12 13bhps (L to R): 3 5 7.5 10 15 20 25 30 40Note: Shaded Area – Recommended Operating RangeMP – Minimum Point (VAV Applications) = 7,500 cfm
Airflow (1000 cfm)
Tota
lSta
ticP
ress
ure
(in.w
g)A
B3 5 7.5
Section 6 – Fan Volume Control
Adjusted System Curve
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System BypassConstant Volume Rooftop
Variable Volume and Temperature System Application
Rooftop Fancfm is constant
Direct ConnectedBypass Damper
BackdraftDamper
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Legend- rpm - bhp MSE - Max Static Eff. SC -System Curve RP - Rated Point = 15,000
rpm = 1010 bhp = 17.8 Class II Max. rpm = 1217rpms (*100, L to R): 3 4 5 6 7 8 9 10 11 12 13bhps (L to R): 3 5 7.5 10 15 20 25 30 40Note: Shaded Area – Recommended Operating Range
System Bypass Fan CharacteristicsRP = 15,000 cfm
NO FAN cfmREDUCTION
OCCURS
15 20
Airflow (1000 cfm)
Tota
lSta
ticP
ress
ure
(in.w
g)A
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Riding the Fan Curve
Airflow
Sta
ticP
ress
ure
Dcfm
Dp
Reduced cfmresulting frompart load
Design orrated point (RP)
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Legend- rpm - bhp MSE - Max Static Eff. SC -System Curve RP - Rated Point = 15,000
rpm = 1010 bhp = 17.8 Class II Max. rpm = 1217rpms (*100, L to R): 3 4 5 6 7 8 9 10 11 12 13bhps (L to R): 3 5 7.5 10 15 20 25 30 40Note: Shaded Area – Recommended Operating RangeMP – Minimum Point (VAV Applications) = 7,500 cfm
Riding the Fan Curve Characteristics“Wasted Static”is absorbed by
terminalsA
B 3 5 7.5
Airflow (1000 cfm)
Tota
lSta
ticP
ress
ure
(in.w
g)
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
% Air flow Airflow(cfm)
Fan StaticPressure*
SystemStatic
Pressure**
Fan Static Pressureminus SystemStatic Pressure
bhp*** % bhp****
100% 15,000 4.0 4.0 0 17.8 100%90% 13,500 4.15 3.24 0.91 15.7 88%80% 12,000 4.25 2.56 1.96 13.3 75%70% 10,500 4.3 1.96 2.34 12.0 67%60% 9,000 4.25 1.44 2.81 9.81 55%50% 7,500 4.15 1.0 3.15 8.0 45%
Discharge Dampers and Riding the Fan Curve
* Fan static pressure is from the fan curve** System static is determined using the second fan law*** bhp is from the fan curve**** % bhp is the percent as compared to the maximum bhp
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
% Air flow Airflow (cfm) bhp % bhp
100% 15,000 17.8 100%
90% 13,500 15.7 88%
80% 12,000 13.3 75%
70% 10,500 12.0 67%
60% 9,000 9.81 55%
50% 7,500 8.0 45%
Discharge Dampers and Riding the Fan Curve
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Inlet Guide Vanes Configuration
Actuator Shaft(actuator not
shown)
Fan BearingLube Line for
Bearing
Inlet Vanes
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Inlet Guide Vanes bhp ChartEffect of Inlet Guide Vane Position on bhp
Airfoil Centrifugal Fan Horizontal Draw-Thru
cfm (x 1000)
Bra
keH
orse
pow
er(P
erce
ntof
Max
) SC
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Inlet Guide Vane Static Pressure ChartEffect of Inlet Guide Vane on Static Pressure
cfm (x 1000)
Stat
icPr
essu
re(P
erce
ntof
Max
)
SC
Airfoil Centrifugal Fan Horizontal Draw-Thru
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Variable Frequency Drive
USER INTERFACE
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Eddy Current Coupling
1. Eddy Current Coupling
2. Fan Motor
3. Special Cabinet Extension(as required to accommodateeddy current coupling)
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Legend- rpm - bhp MSE - Max. Static Eff. SC -System Curve RP - Rated Point
rpm = 2210 bhp = 18.8 Class II Max. rpm = 2442rpms (*100, L to R): 8 10 12 14 16 18 20 24 26bhps (L to R): 3 5 7.5 10 15 20 25 30 40Note: Shaded Area – Recommended Operating RangeMP – Minimum Point (VAV Applications) = 7500 cfm
Airflow (1000 cfm)
Tota
lSta
ticP
ress
ure
(in.w
g)
Speed Control Using a VFD
3 5
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Fan Modulation Methods
% Air flow Airflow(cfm)
SystemStatic
Pressure*Fan rpm
VFDbhp**VFD
% bhp***VFD
% bhpDischarge
Dampers andRiding the Fan
Curve
100% 15,000 4.0 2210 18.8 100% 100%
90% 13,500 3.525 2000 14.1 75% 88%
80% 12,000 3.1 1810 10.8 57% 75%
70% 10,500 2.725 1625 7.6 40% 67%
60% 9,000 2.4 1475 5.9 31% 55%
50% 7,500 2.125 1300 4.1 22% 45%
* System static is determined using the second fan law** bhp is from the fan curve*** % bhp is the percent as compared to the maximum bhp
Section 6 – Fan Volume Control
Copyright © Carrier Corp. 2005
Fan Modulation Methods
% Design Airflow
Riding the Fan Curve
Inlet GuideVanes
%D
esig
nbh
p
VFD Speed Control
Section 6 – Fan Volume Control
Discharge Dampers
Copyright © Carrier Corp. 2005
SECTION 7
Fan Stability
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
Typical VAV VFD Fan CharacteristicsFull cfm =15,000 (RP)
Min. cfm =7500 (MP)
Section 7 – Fan Stability
Legend- rpm - bhp MSE - Max. Static Eff. SC -System Curve RP - Rated Point
rpm = 2210 bhp = 18.8 Class II Max. rpm = 2442rpms (*100, L to R): 8 10 12 14 16 18 20 24 26bhps (L to R): 3 5 7.5 10 15 20 25 30 40Note: Shaded Area – Recommended Operating RangeMP – Minimum Point (VAV Applications) = 7500 cfm
Airflow (1000 cfm)
Tota
lSta
ticP
ress
ure
(in.w
g)
Copyright © Carrier Corp. 2005
Input Screen VAV Fan
Section 7 – Fan Stability
Copyright © Carrier Corp. 2005
Manual Plot of System Curve
% cfm cfm System and FanStatic Pressure (in. wg)
100 15,000 4.090 13,500 3.52580 12,000 3.170 10,500 2.72560 9,000 2.450 7,500 2.125
System Cooling Design: 15,000 cfmSystem Static Pressure: 4 in. wgMinimum Airflow: 7,500 cfmMinimum Static Pressure Set Point: 1.5 in. wg
Section 7 – Fan Stability
Copyright © Carrier Corp. 2005
SECTION 8
VFD Energy Savings in VAV Systems
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
The three fan laws state:• Airflow varies directly
with the fan speed
• Static pressure varies as thesquare of the fan speed
VFD Energy Savings
Section 8 – VFD Energy Savingsin VAV Systems
Horsepower varies as the• Horsepower varies as thecube of the fan speed
Copyright © Carrier Corp. 2005
SECTION 9
VAV Fan Control, Tracking,and Pressurization
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
VAV Fan Control
Section 9 – VAV Fan Control, Tracking,and Pressurization
1/2 to 2/3 Duct Length
Copyright © Carrier Corp. 2005
Supply and Return Fan – VAV System
ReturnDamper
Constant airflowdifferential ismaintainedbetween supplyand return fans.
Section 9 – VAV Fan Control, Tracking,and Pressurization
ExhaustDamper
OutdoorDamper
Copyright © Carrier Corp. 2005
Supply – Exhaust Fan VAV System
Inside SpacePressure Sensor
0.05 in. wg
Outside ReferencePressure Sensor
ReturnDamper
The insidespace pressuresensor, controlsthe exhaust fan tomaintain slightpositive pressure.
Section 9 – VAV Fan Control, Tracking,and Pressurization
ExhaustDamper
OutdoorDamper
Copyright © Carrier Corp. 2005
SECTION 10
Summary
FANS IN VARIABLEAIR VOLUME SYSTEMS
Copyright © Carrier Corp. 2005
Summary
• Explained the impact of fan regulation• Identified the types of fans used in VAV• Examined previous and current methods of
fan volume control• Utilized fan curves to demonstrate stable
fan selections• Compared fan volume control methods for
energy savings• Examined fan static pressure control,
tracking, and pressurization
Section 10 – Summary
Copyright © Carrier Corp. 2005
Work Session
Work Session
FANS IN VAV SYSTEMS
Work Session1. True or False? The drive losses in an eddy current coupling are less than that in a VFD.
____________________
2. Which fan type is best for VAV applications and why?__________________________________________________________________________________________________________________________________________________
3. True or False? VAV systems have the ability to track changes in building loads.____________________
4. Which method of volume control is the most cost effective and efficient?____________________
5. Discharge dampers are used with which type of fan?
Copyright © Carrier Corp. 2005
Technical Development Program
Thank YouThis completes the presentation.
TDP-613 Fans in Variable Air Volume SystemsArtwork from Symbol Library used by permission ofSoftware Toolboxwww.softwaretoolbox.com/symbols