A.O. Smith BL-100 - Vent Pipe Requirements

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If the water heater is being installed as a replacement for an
existingheaterinpre-existingventing,athoroughinspectionof
existingventingsystemmustbeperformedpriortoanyinstallation
work.
VENT DAMPERS - Any vent damper, whether it is operated
thermallyorotherwisemustberemovedifitsuseinhibitsproper
draftingofthewaterheater.
ThermallyOperatedVentDampers:thisgas-firedwaterheater
has a thermal efficiency at or above 80%which mayproduce
arelativelylowflue gas temperature.Suchtemperaturesmay
not be high enough to properly open thermally operated vent
dampers.Thiswouldcausespillageofthefluegasesandmay
cause carbon monoxide poisoning. Vent dampers must bear
evidenceofcertificationascomplyingwiththecurrenteditionof
theAmericanNationalStandardANSIZ21.66CGA6.14(cover ing
electrically and mechanically actuated vent dampers). Before
installationofanyventdamper,consultthelocalgasutilityfor
furtherinformation.
Toinsureproperventingofthisgas-firedwaterheater,thecorrect
ventpipediametermustbeutilized.Anyadditionsordeletions
ofothergasappliancesonacommonventwiththiswaterheater
mayadverselyaffecttheoperationofthewaterheater.Consult
yourgassupplierifanysuchchangesareplanned.
Forproperventingincertaininstallations,alargerdiametervent
pipemaybenecessary.Consultyourgassuppliertoaidyouin
determiningtheproperventingforyourwaterheaterfromthevent
tablesinthecurrenteditionoftheNationalFuelGasCodeANSI
Z223.1/NFPA 54 or the Natural Gas and Propane Installation
Code CAN\CSA B 149.1.
Periodicallychecktheventingsystemforsignsofobstructionor
deteriorationandreplaceifneeded.
Thecombustionandventilationairflowmustnotbeobstructed.
The water heaterwithdraft hoodinstalledmustbe connected
toachimneyorlistedventpipesystem,whichterminatestothe
outdoors. Never operate the water heater unless it is vented to the
outdoorsandhasadequateairsupplytoavoidrisksofimproper
operation, explosion or asphyxiation.
Alignthelegsofthedrafthoodwiththeholesprovided.Insert
the legsand securethedraft hoodto thewaterheater’stop
withthefourscrewsprovidedasshowninFigure13.Donot
alterthedrafthoodinanyway.Ifyouarereplacinganexisting
waterheater,besuretousethenewdrafthoodsuppliedwith
the water heater.
Obstructed or deteriorated vent systems may present serious
health risk or asphyxiation.
DRAFT HOOD
SHEET METAL SCREWS (FOUR PROVIDED)
LEGS
HOLE
INSTALL THE DRAFT HOOD WITH
THE FOUR SCREWS PROVIDED.
JACKET TOP
HOLE
LEGS
FIGURE 13.
The vent pipe from the water heater must be no less than the
diameter of the draft hood outlet on the water heater and must
slopeupwardatleast1/4inchperlinearfoot(21mmpermeter).
SeeFigure14.
Allvent gases mustbe completely vented to theoutdoors of the
structure(dwelling).Installonlythedrafthoodprovidedwiththe
newwaterheaterandnootherdrafthood.
Ventpipesmustbesecuredateachjointwithsheetmetalscrews.
FIGURE 14.
Theremustbeaminimumof6”(153mm)clearancebetweensingle
wall vent pipe and any combustible material.  Fill and seal any
clearancebetweensinglewallventpipeandcombustiblematerial
withmortarmix,cement,orothernoncombustiblesubstance.For
other than single wall, follow vent pipe manufacturer’s clearance
specications.Toinsureatighttoftheventpipeinabrickchimney,
sealaroundtheventpipewithmortarmixcement.
Failure to have required clearances between vent piping and
combustiblematerialwillresultinarehazard.
Be sure vent pipe is properly connected to prevent escape of
dangerousuegaseswhichcouldcausedeadlyasphyxiation.
Chemicalvaporcorrosionoftheflueandventsystemmayoccur
ifairforcombustioncontainscertainchemicalvapors.Spraycan
propellants,cleaningsolvents,refrigeratorandairconditioner
refrigerants,swimming pool chemicals, calcium and sodium
chloride,waxes, bleach and process chemicals are typical
compoundswhicharepotentiallycorrosive.