ZkWARNING I
AWARNING
Inthe past,therewas noproblemin bringinginsufticientout-
door airtorcembustien.Infiltrationprovidedalllie airthatwas
needed.Intoday'shomes,_ght _n p_ctJcesmakeit
necessary tobdnginairfrom outsideforcombustion.Takeinto
accountthat exhaustfans, appliancevents, chimneys,and
fireplaces forceadditionalairthat couldbeusedfor oombus-
tion outof the house.Unless outsideair is brm,'ghtintothe
houseforcombustion,negative pressure(outsidepressureis
greaterthan insidepressure)willbuildtothe pointthata down-
draft canoccurin_e fumacevent pipeorchimney.As a result,
cembustiongasesenterhe living spacecreatinga potentially
dangeroussituation.
In the absenceof localcodes concerning air forcombustion
and ventilation,use the guidelines and proceduresin his
sectionto installG24M furnaces to ensureefficientandsafe
operation.You mustconsidercombustionair needsand re-
quirementsfor exhaustventsend gaspiping.A portionof this
informationhasbeenreprinted withpermission from theNa-
tionalFuelGas Code(ANSI-7_'_3.1).Thisreprinted material
isnot the completeandofficialpositionof theANSIonthe ref-
erencedsubject,whichis representedonly bythe standardin
its entirety.
In Canada, refer to the standard CAN/CGA B149.1 and
B149.2 installationcodes.
,CAUTION
Allgas-firedappliancesrequire air forthe combustion pro-
cess. If sufficientcombustion air is not available,the fur-
nace or other appliance willoperate inefficientlyand un-
safely.Enoughair must be providedtomeetthe needsofall
fuel-burning appliances and apptiances such as exhaust
fans whichforce airout ofthe house. When fireplaces, ex-
haustfans, or clothesdryersare used at the same timeas
the furnace, much more air is required to ensure proper
combustionand to prevent a downdraft. Insufficientair
causesincompletecombustionwhichcan resultincarbon
monoxide.
Inadditionto providingcombustion air,freshoutdoorairdi-
lutes contaminants in the indoor air. These contaminants
may include bleaches, adhesives, detergents, solvents
and other contaminantswhichcan corrodefurnacecompo-
nents.
The requirementsfor providingair for combustionand ven-
tilationdependlargely onwhether the furnace is installedin
an unconfinedor a confinedspace.
Unconfined Space
An unconfinedspace is an area such as a basement or
largeequipmentroomwith a volume greaterthan50 cubic
feet (1.42 m3) per 1,000 Btu (.29 kW) perhourof the com-
binedinput ratingof all appliances installedinthatspace.
This space also includes adjacent roomswhich are not
separated bya door.Thoughan area may appear tobe un-
confined,it might be necessary to bdngin outdoorair for
combustion if the structuredoesnot provide enoughair by
infiltration.If the furnace is located in a building of tight
constructionwith weather stripping and caulkingaround
the windows and doors, followthe procedures in the air
from outsidesection.
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