Specifications

10
VI Air for Ventilation
WARNING
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.
  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overheating
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National
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:
• 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.
• 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.
• 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
FCM120andawaterheateraretobeinstalledinaroommeasuring6ft–3inx7ftwithan8ftceiling.The
waterheaterhasaninputof30000BTU/hr:
TotalinputinthousandsofBTU/hr=(120000BTU/hr+30000BTU/hr)/1000=150MBTU/hr
Volumeofroom=6.25ftx7ftx8ft=350ft
3
350/150=2.33.Since2.33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(Figure6.1).Theminimumopeningdimensionis3inches.
• IftheFCM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.
Step2b:Iftheboileristobeplacedinanunconnedspacethenaturalinltrationintotheboilerroomwillprovide
adequateairforventilationwithoutadditionalopeningsintoboilerroom.