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OUTDOOR COMBUSTION AIR MUST BE PIPED TO THE AIR INTAKE. NEVER PIPE COMBUSTION
AIR FROM AREAS CONTAINING CONTAMINATES SUCH AS SWIMMING POOLS AND LAUNDRY
ROOM EXHAUST VENTS. CONTAMINATED COMBUSTION AIR WILL DAMAGE THE BOILER
ANDMAYCAUSEPROPERTYDAMAGE,PERSONALINJURYORLOSSOFLIFEANDWILLVOID
THEMANUFACTURER’SWARRANTY.
V Air for Ventilation
Airforcombustionmustalwaysbeobtaineddirectlyfromoutdoors,howeversufcientairforventilationmust
stillbeprovidedintheboilerroom.Airforventilationisrequiredtokeepvariousboilercomponentsfromover-
heatingandisalwaysobtainedfromindoors.Toensureanadequateventilationairsupply,performthefollowing
steps:
Step1:Determinewhethertheboileristobeinstalledinaconnedspace-AconnedspaceisdenedbytheNa-
tional Fuel Gas Codeashavingavolumelessthan50cubicfeetper1000BTU/hrinputofallappliancesinstalled
inthatspace.Todeterminewhethertheboilerroomisaconnedspace:
1) TotaltheinputofallappliancesintheboilerroominthousandsofBTU/hr.Roundtheresulttothenext
highest1000BTU/hr.
2) Findthevolumeoftheroomincubicfeet.Thevolumeoftheroomincubicfeetis:
Length(ft)xwidth(ft)xceilingheight(ft)
Incalculatingthevolumeoftheboilerroom,considerthevolumeofadjoiningspacesonlyifnodoorsare
installedbetweenthem.Ifdoorsareinstalledbetweentheboilerroomandanadjoiningspace,donotconsider
thevolumeoftheadjoiningspace,evenifthedoorisnormallyleftopen.
3) DividethevolumeoftheboilerroombytheinputinthousandsofBTU/hr.Iftheresultislessthan50,the
boilerroomisaconnedspace.
Example:
A CHG225 and a water heater are to be installed in a room measuring 6ft – 3 in x 7ft with an 8 ft ceiling. The
water heater has an input of 30000 BTU/hr:
Total input in thousands of BTU/hr = (225000 BTU/hr + 30000 BTU/hr) / 1000 = 255 MBTU/hr
Volume of room = 6.25 ft x 7 ft x 8 ft = 350 ft3
350/255 = 1.37. Since 1.37 is less than 50, the boiler room is a conned space.
Step2a:Iftheboileristobeplacedinaconnedspace,providetwoopeningsintotheboilerroom,onenearthe
oorandoneneartheceiling.Thetopedgeoftheupperopeningmustbewithin12”oftheceilingandthebottom
edgeoftheloweropeningmustbewithin12”oftheoor(Fig5.1).Theminimumopeningdimensionis3inches.
• IftheCHGboileristheonlygas-burningapplianceintheboilerroom,theseopeningsmusteachhavea
minimumfreeareaof100squareinches.
• Ifothergas-burningappliancesareintheboilerroom,sizetheopeningsinaccordancewiththeappliance
manufacturer’sinstructionsortheNational Fuel Gas Code.Minimumopeningfreeareais100square
inchesevenifopeningrequirementsforotherappliancesareless.
• Ifthetotalvolumeofboththeboilerroomandtheroomtowhichtheopeningsconnectislessthan50
cubicfeetper1000BTU/hroftotalapplianceinput,installapairofidenticalopeningsintoathirdroom.
Connectadditionalroomswithopeningsuntilthetotalvolumeofallroomsisatleast50cubicfeetper
1000BTU/hrofinput.
• The“freearea”ofanopeningtakesintoaccounttheblockingeffectofmesh,grills,andlouvers.Where
screensareused,theymustbenonerthan¼”(4x4)mesh.