Need for Duct Leakage

8/13/2019 Need for Duct Leakage

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TESTINGFOR

DUCT

LEAKAGE

Engineered Air Balance Co., Inc.

Spring, Texas


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WhatShouldBeSpecifiedAssociatedAirBalance ASHRAE 2012DuctConstructionChapter

TypeofSystem Minimum

Test

Maximum

Allowable

System

Condition

TestPressure1,7

in.wc(Pa)

Allowabl

System

Pressure , Leakage Leakage

1.Fractionalhorsepowerfan

systems;fan

coils,

small

exhaust/supplyfans,andresidential

0.50WC

(125 pa)

2% Operating

System

Operating

Pressure

5%

systems

Construction

.

2.Smallsystems;splitDXsystems 1.00WC 2%

(940l/s),

and

residential

systems

1 Testpressureshouldnotexceedthepressureratingoftheduct.7Itisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureifthepossibility

o ans uo ex s se er n sys emsor nsys emsw smo e re ampercon ro .


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WhatShouldBeSpecified

AssociatedAirBalance ASHRAE 2012DuctConstructionChapterounc tan ar ystemsan qu pment an oo


TestPressure

Maximum

Allowable

System

Condition

TestPressure1,7,in.wc

Allowable

System1,7

Leakage (Pa) Leakage

3.VAVandCAVboxesand

associateddownstream

2

1.00WC

(250pa)

2% Operating

System

Not

Addressed

4.Singlezone,multizone,

returnducts,andexhaust

ducts stems

2.00WC

(500pa)

2% Operating

System

Operating

Pressure

5%

Durin 2.0 500 5%

Construction

1 Testpressureshouldnotexceedthepressureratingoftheduct.7Itisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureifthepossibilityoffanshutoff

.


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AssociatedAirBalanceCouncilAABCStandard ASHRAE 2012DuctConstructionChapterSystemsandEquipmentHandbook


Test

Pressure

1,7

Maximum

Allowable

Leakage

System

Condition

TestPressure1,7,

in.wc(Pa)

Allowable

System

Leakage. cons an vo ume uc s

inchasesandconcealed

spaces,mainreturnducts

onVAV8 andCAV8 systems

.

(745pa)

pera ng

System

o resse

During

Construction

NotAddressed

1 Testpressureshouldnotexceedthepressureratingoftheduct.7Itisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureifthe

possibilityoffanshutoffexistseitherinVAVsystemsorinsystemswithsmoke/firedampercontrol.8

.

outlet,thentheboxshouldbeincludedintheupstreamleakagetesting.


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WhatShouldBeSpecifiedAssociatedAirBalanceCouncilAABCStandard ASHRAE 2012DuctConstructionChapterSystemsandEquipmentHandbook

Typeof

System Minimum

Test

Pressure1,7

Maximum

Allowable

Leaka e

System

Condition

TestPressure

1,7,

in.wc(Pa)

Allowable

System

Leaka e

6.SupplyductsforVAV8 and

CAV

8

systemsVAVandCAVterminal

4.00WC

(995

pa)

1% Operating

System

Operating

Pressure

5%

boxestestedwith

upstreamductwork

Construction

4.0 (1000)

Downstream

Box: 1.0(250)

estpressure

s ou

not

excee

t e

pressure

rat ng

o

t e

uct.7Itisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureifthe

possibilityoffanshutoffexistseitherinVAVsystemsorinsystemswithsmoke/firedampercontrol.8 Itisassumedthattheprimaryairdamperislocatedattheterminalboxinlet. Ifinsteadthisdamperis

att eterm na oxout et,t ent eterm na oxs ou e nc u e nt eupstream ea agetest ng.


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AssociatedAirBalance ASHRAE 2012DuctConstructionChapterounc tan ar ystemsan qu pment an oo

TypeofSystem Minimum Maximum System TestPressure1,7, Allowable

Test

Pressure1,7Allowable

Leakage

Condition in.wc(Pa) System

Leakage

7.Dual

duct

systems,

both

6.00

WC 1% Operating

Operating

5%

o uc an co uc pa ys em ressure

During

Construction

6.0(1500) 5%

.

g

pressure

n u c on

system .

(1495pa) . pera ng

System pera ng

Pressure

During

Construction

6.0(1500) 5%

1 Testpressureshouldnotexceedthepressureratingoftheduct.

5 Largeinduction

systems

may

have

higher

pressure

requirements,

i.e.,

10

WC

(2490

pa)

7Itisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureifthe


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ounc an ar ys emsan qu pmen an ooTypeofSystem Minimum

Test

Maximum

Allowable

System

Condition

TestPressure1,7,

in.wc(Pa)

Allowable

System

Pressure1,7 Leakage Leakage

9.Manifoldedexhaustsystems

Exhaustsystems

for

labs

6.00WC6

(1495pa)

0.5% Operating

System

NotAddressed

During

Construction

NotA resse

10.Grease ductsystems 4.00WC

(995pa)

0% Operating

System

NotAddressed

DuringConstruction

NotAddressed

1 Testpressureshouldnotexceedthepressureratingoftheduct.6 Largemanifoldexhaustsystemsmayhavehigherpressurerequirements,i.e.,10WC(2490pa)7Itisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureifthe

possibilityof

fan

shut

off

exists

either

in

VAV

systems

or

in

systems

with

smoke/fire

damper

control.


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Typeof

System Minimum

Test

Pressure1,7

MaximumAllowable

Leakage

System

ConditionTest

Pressure

1,7,

in.WC(Pa)Allowable

System

Leakage

11.VAV8 andCAV8 return

systems

Not

Addressed

Operating

System

Operating

Pressure

5%

During

Downstream 5%

Construction box:3.0(750)

Upstreambox:

1.0(250)

1 Test ressureshouldnotexceedthe ressureratin oftheduct.

7Itis

recommended

that

the

pressure

rating

of

the

duct

be

equal

to

the

fan

shut

off

pressure

ifthe

possibilityoffanshutoffexistseitherinVAVsystemsorinsystemswithsmoke/firedampercontrol.8 Itisassumedthattheprimaryairdamperislocatedattheterminalboxinlet. Ifinsteadthisdamperis

attheterminalboxoutlet thentheterminalboxshouldbeincludedintheu streamleaka etestin .


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AssociatedAirBalance ASHRAE 2012DuctConstructionChapterCouncilAABCStandard SystemsandEquipmentHandbook


Test

Maximum

Allowable

System

Condition

TestPressure1,7,in.WC

Allowabl

eSystem

Pressure1,7

Leakage (Pa) Leakage

12.

Chilled

beam

primary

su l

2.00 WC

(500 pa)

1% Operating

S stem

Operating

Pressure

5%

During

Construction

4.0(1000) 5%

1 .

7ItisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureifthepossibilityoffanshutoffexistseitherinVAVsystemsorinsystemswithsmoke/firedampercontrol.


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ssoc a e r a anceCouncilAABCStandard

uc ons ruc on ap erSystemsandEquipmentHandbook


Test

Maximum

Allowable

System

Condition

TestPressure1,7,

in.wc(Pa)

Allowable

System

Pressure1,7 Leakage Leakage

Specified design

15.Airhandlingunits

.

(2500pa)

1%

Sitetest by

Manufacturer

pressure

Operating

Pressure

2.0(500)

1 .

7Itisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureifthe

possibility

of

fan

shut

off

exists

either

in

VAV

systems

or

in

systems

with

smoke/fire

damper

control.


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AssociatedAirBalanceCouncilAABCStandard ASHRAE 2012DuctConstructionChapterSystemsandEquipmentHandbook

Test

Pressure1,7Allowable

Leakage

Condition

1,7,in.wc(Pa)

System

Leakage

16.Multizone

supply

Item

4

2% Operating

Operating

5%

systems;Multizone

returnsystems;

Multizoneexhaust

above

2.00WC

(500Pa)

System Pressure

During

Construction

2.0(500) 5%

1 Testpressureshouldnotexceedthepressureratingoftheduct.7Itisrecommendedthatthepressureratingoftheductbeequaltothefanshutoffpressureif

the ossibilit offanshutoffexistseitherinVAVs stemsorins stemswithsmoke firedam er

control.


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ForAir

Handling

Units

(AHU)with

total

static

pressures

(TSP)

below

4WCIwouldsuggestthetestrequirementbe2xTSPnottoexceed

10 WC.Suggestpane e ection eteste uring t eAHU

pressuretest.

Instrumentationused

to

measure

the

pressure

across

the

orifice

tubemusthave.01WCresolution.


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DeflectionTesting

Deflectionlimit

of

L/250

shall

be

demonstrated.

Measurements

shallbetakenatmidpointofLusingdialindicatorsreadingin

1 1000t s. Mountingo ia in icatorss a ein epen ento t e

unitcasing. Multiplemeasurementsshallbemade. Dialindicator

shallbe

mounted

at

mid

point

of

L

on

the

seams.

L

is

defined

as

theheightofthelargestpanelonthesidesoftheAHU,widthofthe

largestpanelacrossthetopoftheAHU,andthesmallerofwidthor

heightofthelargestpanelfortheendsoftheAHU. Theseare

knownas

the

governing

panels.


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IssuesofSealingDucttoaLeakageClassandSealClass

Case1:PriortoSMACNAHVACAirDuctLeakageTestManual,1985two

ent ca p aseso aresearc u ngwere u t y erentcontractors.

TheAHUsystemsweredualduct.Phase1bycontractorArequired

increasingthe

RPM

and

loading

the

125HP

motors

(156

amps)to

maintain

.

requireddecreasingtheRPMwhichloweredtheampdraw(92amps)to

maintainthestaticpressureattheendofthesystem.


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Case2:

Two

identical

ten

story

office

buildings

were

built

by

the

same

contractors.Theoutsideair(OSA)andtoiletexhaustductrisersinthe

.

identicalsizesandhadthesamerateddesignairflow.Thespecification

requiredapressuretestof3.0andleakagetonotexceed2%.BuildingA

.

ductsealingbyteamBfailedmanytimesandfinallypassedafter3weeks

ofextrasealing.


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Case3:

A

96

x96

main

exhaust

duct

was

designed

for

180,000

CFM.

The

sealclasswasAandtheleakageclasswas6.Thespecificationsrequired

.

andfoundtheleakagetobebetween8%to15%.Theductwasinstalledin

aninterstitialspace andthetopoftheductranbetweenthebeams.An

andnotthetopandbottom.


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Case4:

Connection

of

plenum

boxes

to

diffusers.

On

ahard

ducted

systemthediffuserswereconnectedtoplenumboxes.Thediffusers

wereinsta e wit zipscrewsoneac si e.Ourtesting oun 15%

leakage.Theplenumboxeshadtobedisconnectedfromthebranch

ductand

the

diffuser

and

plenum

removed

to

properly

seal

the

connection.Afterthediffusersandplenumboxeswerereinstalled

noleakagewasdetected.


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ReportingDuctLeakage Job Number

Job

Name DescriptionofDuctTested

er orme yan nesses

Equipmenttagordesignationoftheprimarymover

DesignCFM

of

Test

Section

TestEquipmentOrificeSizeandCalibrationDate

RequiredSP ActualSP

AllowableLeaka einCFMDeterminedb %ofDuctBein Tested

ActualLeakage

CFM

Pass/Fail


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AnticipatedCost

Thesecostsarebasedontheassumptionthatbuildingsare

designedontheaverageof1CFM/Ft2 andthecostisapproximately$2.00/ Ft2

ShouldbeSpecifiedAbove CFM Cost/Year=Leak %

xCFMx$2.00

Construction ChapterCost/Year=Leak %xCFMx$2.00

1.&2.SmallSystems

(multiples)

2000 $80 $200

3.TerminalBox Downstream

Ductwork(multiples)1570 $62.80 $157.00

. , ,

VAV,CAV

. .


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AnticipatedCost

TypeofSystemFromWhatShouldbeSpecifiedAbove MaximumCFM AABC StandardsCost/Year=Leak % x CFM x

ASHRAE2012DuctConstructionCha ter Cost Year =

$2.00

Leak %xCFMx$2.00

5.DuctsinChases 50000 $1000 $5000

6.VAVandCAVSupplyDucts 80000 $1600 $8000

7.DualDuctS stems 150000 $3000 $15000

8.High

Pressure

Induction 100000 $1000 $10000

9.ManifoldExhaustSystem 200000 $2000 $20000

. rease uc s o resse

11.VAV&CAVReturnSystems 100000 $1000used1% $10000


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AnticipatedCost

TypeofSystemFromWhatShouldbeSpecifiedAbove MaximumCFM AABCStandardCost/Year=Leak %x CFM x 2.00

ASHRAE2012DuctConstructionCha ter Cost Year=Leak %xCFMx$2.00

12.ChilledBeam 20000 $200used.5% $2000

13.Supply&Returnlocated

Outdoors

30000 $0used0% $3000

14.Exhaust

Ductwork 200000 $4000

used

1% $8000

15.AHUs 150000 $3000 $3000

16. Multizone S stems 25000 1000 used 2% 2500


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AnticipatedCost

The$2.00

per

CFM

came

from

an

estimated

value

when

TC

5.2

was

analyzingterminalboxleakage.ThesamecostperCFMwasfound

to etrueina7400 t o icewit 5roo topsing ezoneunits.

ResearchbuildingoperatorshavestatedtheircostperCFMranges

between$4.00

to

$8.00

per

CFM

depending

on

how

many

100%

OSAsystemsareservingthebuildingandhowmanyspaceshave

highairchangerates.


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WhatDoesASHRAEStandard90.1Addendumcq add

6.4.4.2Ductwork

and

Plenum

Leakage

6.4.4.2.1DuctSealing.Ductworkandallplenumswithpressureclass

ratingsshallbeconstructedtosealclassA,asrequiredtomeetthe

requirementsofsection6.4.4.2.2,andwasstandardindustry

practice(see

Informative

Appendix

E).

.....

All

connections

shall

be

sealed,includingbutnotlimitedtospinins,taps,otherbranch

connections,accessdoors,accesspanels,andductconnectionsto

equipment.Sealingthatwouldvoidproductlistingsisnotrequired.

Spirallock

seems

need

not

be

sealed.

All

duct

pressure

class

ratings

shallbedesignatedinthedesigndocuments.


26/28

WhatDoesASHRAEStandard90.1Addendumcq add

6.4.4.2.2DuctLeakageTests.Ductworkthatisdesignedtooperateat

staticpressuresinexcessof3in.wcandallductworklocated

outdoorsshall

be

leak

tested

according

to

industry

accepted

test

rocedures seeInformativeA endixE .Re resentativesections

totalingnolessthan25%ofthetotalinstalledductareafor

designatedpressureclassshallbetested.Allsectionsshallbe

selected b the buildin owner or the desi nated re resentative of

thebuildingowner.Positivepressureleakagetestingisacceptable

fornegativepressureductwork.Themaximumpermittedduct

= 0.65 = max max

leakageCFM/100

ft2 duct

surface

area.

CL=for,ductleakageclass,

CFM/100ft2 ductsurfaceareaat1in.wc.P=testpressure,which

, .


27/28

Summary

Ihaveseenonseveralprojects sampleleakagetestingofthe

ductworkspecifiedandthesealingofthesampleducttobebetter

thanthe

remaining

ductwork.

Iwould

suggest

that

100%

of

the

ductworkbetested.

TosaveenergyIwouldsuggestthatductworkabove3WCbe

testedattheductratedpressureandnotexceed1%leakage.

e uc ra e pressures ou ew a era e ansys ems u

offpressurewouldbeifadamperfailed.Thestaticpressuresetting

forthelimitswitchesmustbesetbelowthemaximum test

pressure

o

t e

uct. Tonotpressuretestductworkandassumethesealantwillbe

appliedproperlyhassavedmoneyonthefrontendbutcostthe

ownerdearlythroughoutthelifeofthesystem.


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QUESTIONS

IT COULD BE WORSE

Need for Duct Leakage

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