State Industries A B C D E F 100 Water Heater User Manual


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afreeareaofonesquareinchper1000Btu/hr(22cm
2
/kW)ofthe
totalinputofallappliancesintheenclosure,butnotlessthan100
squareinches(645cm
2
).
Iftheconnedspaceiswithinabuildingoftightconstruction,airfor
combustion and ventilation must be obtained from outdoors. When
directlycommunicatingwiththeoutdoorsorcommunicatingthrough
verticalducts,twopermanentopenings,locatedintheabovemanner,
shallbeprovided.Eachopeningshallhaveafreeareaofnotless
thanonesquareinchper4000Btu/hr(5.5cm
2
/kW)oftotalinputofall
appliancesintheenclosure.Ifhorizontalductsareused,eachopening
shallhaveafreeareaofnotlessthanonesquareinchper2000Btu/
hr(11cm
2
/kW)ofthetotalinputofallappliancesintheenclosure.
A. ALL AIR FROM INSIDE BUILDINGS: (SeeFigure5and6)
Theconnedspaceshallbeprovidedwithtwopermanentopenings
communicatingdirectlywithanadditionalroom(s)ofsufcientvolume
sothatthecombinedvolumeofallspacesmeetsthecriteriaforan
unconnedspace.Thetotalinputofallgasutilizationequipmentinstalled
inthecombinedspaceshallbeconsideredinmakingthisdetermination.
Eachopeningshallhaveaminimumfreeareaofonesquareinch
per1,000Btuperhour(22cm
2
/kW)ofthetotalinputratingofallgas
utilization
equipmentintheconnedspace,butnotlessthan100square
inches(645cm
2
).Oneopeningshallcommencewithin12inches
(30cm)ofthetopandonecommencingwithin12inches(30cm)ofthe
bottom of the enclosures.
FIGURE 6.
B. ALL AIR FROM OUTDOORS:(SeeFigures7,8and9)
Theconnedspaceshallbeprovidedwithtwopermanentopenings,
onecommencingwithin12inches(30cm)ofthetopandone
commencingwithin12inches(30cm)fromthebottomoftheenclosure.
Theopeningsshallcommunicatedirectly,orbyducts,withtheoutdoors
orspaces(crawlorattic)thatfreelycommunicatewiththeoutdoors.
1. Whendirectlycommunicatingwiththeoutdoors,eachopeningshallhave
aminimumfreeareaof1squareinchper4,000Btuperhour(5.5cm
2
/kW)
oftotalinputratingofallequipmentintheenclosure,seeFigure7.
FIGURE 7.
2.Whencommunicatingwiththeoutdoorsthroughverticalducts,each
openingshallhaveaminimumfreeareaof1squareinchper4,000
Btuperhour(5.5cm2/kW)oftotalinputratingofallequipmentinthe
enclosure,seeFigure8.
3. Whencommunicatingwiththeoutdoorsthroughhorizontalducts,each
openingshallhaveaminimumfreeareaof1squareinchper2,000
Btuperhour(11cm2/kW))oftotalinputratingofallequipmentinthe
enclosure,seeFigure9.
FIGURE 8.
4. When ducts are used, they shall be of the same cross-sectional area
asthefreeareaoftheopeningstowhichtheyconnect.Theminimum
shortsidedimensionofrectangularairductsshallnotbelessthan3
inches(7.6cm),seeFigure9.
FIGURE 9.
5. Alternativelyasinglepermanentopeningmaybeusedwhen
communicatingdirectlywiththeoutdoors,orwithspacesthatfreely
communicatewiththeoutdoors.Theopeningshallhaveaminimum
freeareaof1squareinchper3,000BTUperhour(8.3cm2/kW)of
totalinputratingofallequipmentinenclosure.SeeFigure9A.
FIGURE 9.
6.LouversandGrilles:Incalculatingfreearea,considerationshallbegiven
to
theblockingeffectoflouvers,grillesorscreensprotectingopenings.Screens
usedshallnotbesmallerthan1/4inch(6.4mm)mesh.Ifthefreeareathrough
adesignoflouverorgrilleisknown,itshouldbeusedincalculatingthesize
openingrequiredtoprovidethefreeareaspecied.Ifthedesignandfreearea
isnotknown,itmaybeassumedthatwoodlouverswillbe20-25percentfree
areaandmetallouversandgrilleswillhave60-75percentfreearea.Louvers
andgrillesshallbexedintheopenpositionorinterlockedwiththeequipment
sothattheyareopenedautomaticallyduringequipmentoperation.
7.SpecialConditionsCreatedbyMechanicalExhaustingorFireplaces:
operationofexhaustfans,ventilationsystems,clothesdryersor
replacesmaycreateconditionsrequiringspecialattentiontoavoid
unsatisfactoryoperationofinstalledgasutilizationequipment.
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