Lennox International Inc G50UH-48C-135, G50UH-48C-110, G50UH-60D-135, G50UH-36C-110 Acaution

Inthepast,therewasnoprobleminbringinginsufficientout- doorairforcombustionInfiltrationprovidedalltheairthat. wasneededIntoday'shomes,tightconstructionpractices.

makeit necessaryto bringin airfromoutsideforcombus- tion.Takeintoaccountthatexhaustfans,appliancevents, chimneys,andfireplacesforceadditionalairthatcouldbe usedforcombustionoutofthehouse.Unlessoutsideairis

broughtintothehousefor combustion,negativepressure (outsidepressureisgreaterthaninsidepressure)willbuild tothepointthatadowndraftcanoccurinthefurnacevent pipeorchimneyAsaresult,combustiongasesentertheliv.- ingspacecreating potentiallydangeroussituation.

Intheabsenceoflocalcodesconcerningairforcombus- tionandventilation,usetheguidelinesandproceduresin thissectiontoinstallG50UH(X)furnacestoensureefficient andsafeoperationYoumustconsidercombustionair. needsandrequirementsforexhaustventsandgaspiping. A portionof thisinformationhasbeenreprintedwithper- missionfromtheNationalFuelGasCode(ANSI-Z223.1). Thisreprintedmaterialisnotthecompleteandofficialposi- tionoftheANSIonthereferencedsubject,whichisrepre- sentedonlybythestandardin itsentirety.

In Canada,referto the standardCSAB149installation codes.

ACAUTION

ACAUTION

All gas-fired appliances require air for the combustion pro- cess. If sufficient combustion air is not available, the fur- nace or other appliances will operate inefficiently and un- safely. Enough air must be provided to meet the needs of all fuel-burning appliances and appliances such as exhaust fans which force air out of the house. When fireplaces, ex- haust fans, or clothes dryers are used at the same time as the furnace, much more air is necessary to ensure proper combustion and to prevent a downdraft. Insufficient air causes incomplete combustion which can result in carbon monoxide,

In addition to providing combustion air, fresh outdoor air dilutes contaminants in the indoor air. These contami- nants may include bleaches, adhesives, detergents, sol- vents and other contaminants which can corrode furnace components,

The requirements for providing air for combustion and ven- tilation depend largely on whether the furnace is installed in an unconfined or a confined space,

Unconfined Space

An unconfined space is an area such as a basement or large equipment room with a volume greater than 50 cubic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the com- bined input rating of all appliances installed in that space. This space also includes adjacent rooms which are not separated by a door. Though an area may appear to be un- confined, it might be necessary to bring in outdoor air for combustion if the structure does not provide enough air by infiltration. If the furnace is located in a building of tight construction with weather stripping and caulking around the windows and doors, follow the procedures in the air from outside section.

Confined Space

A confined space is an area with a volume less than 50 cu- bic feet (1.42 m3) per 1,000 Btu (.29 kW) per hour of the combined input rating of all appliances installed in that space. This definition includes furnace closets or small equipment rooms.

When the furnace is installed so that supply ducts carry air circulated by the furnace to areas outside the space contain- ing the furnace, the return air must be handled by ducts which are sealed to the furnace casing and which terminate outside the space containing the furnace, This is especially important when the furnace is mounted on a platform in a confined space such as a closet or small equipment room. Even a small leak around the base of the unit at the platform or at the return air duct connection can cause a potentially dangerous negative pressure condition, Air for combustion and ventilation can be brought into the confined space either from inside the building or from outside,

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