A.O. Smith BTX-80 SERIES 100 Water Heater User Manual


  Open as PDF
of 40
 
13
Such a condition often will result in a yellow, luminous burner
flame, causing sooting of the combustion chamber, burners and
flue tubes and creates a risk of asphyxiation.
Donotinstallthewaterheaterinaconnedspaceunlessan
adequate supply of air for combustion and ventilation is brought in
tothatspaceusingthemethodsdescribedintheConnedSpace
section that follows.
Neverobstructtheowofventilationair.Ifyouhaveanydoubtsor
questions at all, call your gas supplier. Failure to provide the proper
amountofcombustionaircanresultinareorexplosionandcause
property damage, serious bodily injury or death.
UNCONFINED SPACE
AnUnconnedSpaceisonewhosevolumeisnotlessthan50cubic
feetper1,000Btu/hr(4.8cubicmetersperkW)ofthetotalinput
rating of all appliances installed in the space. Rooms communicating
directly with the space, in which the appliances are installed, through
openings not furnished with doors, are considered a part of the
unconnedspace.
Makeup air requirements for the operation of exhaust fans, kitchen
ventilationsystems,clothesdryersandreplacesshallalsobe
considered in determining the adequacy of a space to provide
combustion, ventilation and dilution air.
UNUSUALLY TIGHT CONSTRUCTION
Inunconnedspacesinbuildings,inltrationmaybeadequateto
provideairforcombustion,ventilationanddilutionofuegases.
However,inbuildingsofunusuallytightconstruction(forexample,
weatherstripping,heavilyinsulated,caulked,vaporbarrier,etc.)
additional air must be provided using the methods described in the
ConnedSpacesectionthatfollows.
CONFINED SPACE
AConnedSpaceisonewhosevolumeislessthan50cubicfeet
per1,000Btu/hr(4.8cubicmetersperkW)ofthetotalinputrating
of all appliances installed in the space.
Openings must be installed to provide fresh air for combustion,
ventilationanddilutioninconnedspaces.Therequiredsizeforthe
openings is dependent on the method used to provide fresh air to
theconnedspaceandthetotalBtu/hrinputratingofallappliances
installed in the space.
DIRECT VENT APPLIANCES
AppliancesinstalledinaDirectVentcongurationthatderiveall
air for combustion from the outdoor atmosphere through sealed
intake air piping are not factored in the total appliance input Btu/hr
calculations used to determine the size of openings providing fresh
airintoconnedspaces.
EXHAUST FANS
Where exhaust fans are installed, additional air shall be provided
to replace the exhausted air. When an exhaust fan is installed in
thesamespacewithawaterheater,sufcientopeningstoprovide
fresh air must be provided that accommodate the requirements for
all appliances in the room and the exhaust fan. Undersized openings
willcauseairtobedrawnintotheroomthroughthewaterheater’s
vent system causing poor combustion. Sooting, serious damage to
thewaterheaterandtheriskofreorexplosionmayresult.Itcan
also create a risk of asphyxiation.
LOUVERS AND GRILLES
The free areas of fresh air openings in instructions that follow do not take
in to account presence of louvers, grilles or screens in openings.
The required size of openings for combustion, ventilation and dilution
airshallbebasedonthe“netfreearea”ofeachopening.Wherethe
free area through a design of louver or grille or screen is known, it
shall be used in calculating the size of opening required to provide the
freeareaspecied.Wherethelouverandgrilledesignandfreearea
are not known, it shall be assumed that wood louvers will have 25%
free area and metal louvers and grilles will have 75% free area. Non
motorizedlouversandgrillesshallbexedintheopenposition.
FRESH AIR OPENINGS FOR CONFINED SPACES
The following instructions shall be used to calculate the size, number
and placement of openings providing fresh air for combustion,
ventilationanddilutioninconnedspaces.Theillustrationsshownin
this section of the manual are a reference for the openings that provide
freshairintoconnedspacesonly.Donotrefertotheseillustrations
for the purpose of vent installation. See Installation of Vent System on
pages 19-26 for complete venting installation instructions.
OUTDOOR AIR THROUGH TWO OPENINGS
FIGURE 6.
The confined space shall be provided with two permanent
openings,onecommencingwithin12inches(300mm)ofthetop
andonecommencingwithin12inches(300mm)ofthebottom
of the enclosure. The openings shall communicate directly with
the outdoors. See Figure 6.
Each opening shall have a minimum free area of 1 square inch
per4,000Btu/hr(550mm
2
perkW)oftheaggregateinputrating
of all appliances installed in the enclosure. Each opening shall
notbelessthan100squareinches(645cm
2
).
OUTDOOR AIR THROUGH ONE OPENING
FIGURE 7.
Alternatively a single permanent opening, commencing within 12
inches(300mm)ofthetopoftheenclosure,shallbeprovided.See
 previous next