Installation Instructions (cont'd)
Combustion Air and Ventilation
for Appliances Located in
Unconfined Spaces
Unconfined Spac¢ is a space whosevolume is not lessthan 50
cubic feet per 1,000 Btu per hour of the aggregateinput rating
of all appliancesinstalhd in that space. Roomscommunicating
directlywith the space in which the appliances are installed,
through openings not furnished with doors, are considereda
partofthe unconfinedspace
In unconfined spaces in buildings, infiltrationmay be adequate
to provide air for combustion, ventilationand dilution of flue
gases.However,in buildings of tight construction (forexample,
weather stripping, heavilyinsulated, caulked, vaporbarrier,etc.),
additional air may need to be provided using the methods
describedin Combustion Air and Ventilation for Appliances
Locatedin Confined Spaces,b.
Combustion Air and Ventilation
for Appliances Located in
Confined Spaces
Confined Spacc is a spacewhose volumeis lessthan 50 cubic
feet per 1,000 Btu per hour of the aggregateinput ratingof all
appliancesinstalled in that space.
a. ALL AIR FROM INSIDE BUILDINGS:
(SeePage9 Figure1,and Figure2 below)
The confined space shall be provided with two permanent
openingscommunicating directlywith an additional room(s)
of sufficient volume so that the combined volume of all
spacesmeets the criteria for an unconfined space. The total
input of all gas utilization equipment installed in the com-
bined spaceshallbe consideredin making this determination.
Eachopeningshall have a minimum free area of one square
inch per 1,000 BTU per hour of the total inputratingofafi
gasutilization equipment in the confined space, but not less
than 100squareinches. One openingshallcommencewithin
12 inches of the top and one commencing within 12 inches
of the bottom of the enclosure.
I Figure 2 ]
b. ALL AIR FROM OUTDOORS: (seeFigures3-5)
The confined space shall be provided with two permanent
openings,one commencing within 12 inchesof tee top and
one commencing within 12 inches from the bottom of the
enclosure. The openings shall communicate directly,or by
ducts,with the outdoorsor spaces (crawlor attic) that freely
communicatewith the outdoors.
I Figure 3 ]
1.When direcdycommunicating with the outdoors,each open-
ing shallhavea minimumflee areaof I square inchper 4,000
BTU per hour of total input raring of all equipment in the
enclosure.(SeeFigure3.)
2. When communicatingwith the outdoors through vertical
ducts, each opening shall have a minimum free area of 1
sc!uareinch per 4,000 BTU per hour of total input ratingof
all equipment in the enclosure.(SeeFigure 4.)
1o
Figure 4 ]
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 of total input rating of
all equipment in the endosure. (SeeFigure5.)
[el,-- ....
_i " ....... Ii f I
4.When ductsare used, they shallbe ofthe same cross-sectional
areaas the free area of the openingsto which they connect.
The minimum short side dimensionof rectangularair ducts
shallnot belessthan 3 inches.(SeeFigure5.)
5. Louversand Grilles: In calculating free area, consideration
shall be given to the blocking effect of louvers, grilles or
screensprotecting openings.Screensused shall not be smaller
than ¼inch mesh. If the_ee area through a desi_ of louver
orgrille is known, it should be used in calculating the size
opening recLuiredto provide the free area specified. If the
designand free area is not known, it may be assumed that
woodlouverswillbe 20-25 percent freeareaand metallouvers
and grilles will have 60-75 percent free area. Louversand
grillesshall be fixedin the openposition orinterlocked with
the .equipmentso.that they are openedautomaticallyduring
equipmentoperation.
6. Special Conditions Created by Mechanical Exhaustingor
Fireplaces:Operation of exhaust fans, ventilation systems,
clothesdryersor fireplacesmay create conditions requiring
specialattention to avoid unsatisfactoryoperationof installed
gasutilizationequipment.
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