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Installation
Instructions
(cont'd)
Combustion
Air and Ventilation
for Appliances Located in
Unconfined Spaces
Uncom°med Space is a space whose volume is not less than 50 cubic
feet per 1,000 Btu per hour of the aggregateinput rating of all appli-
ances installed in that space. Rooms communicating directly withthe
space in which the%.pphancesare installed, through openings not fur-
nished with doors, are considered a part of the unconfined space.
In unconfined spaces in buildings, infiltration may be adequate to
provide air for combustion, ventilation and dilution of flue gases.
However, in buildings of tight construction (for example, weather
stripping, heavily insulated, caulked, vapor barrier, etc.), additional air
may need to be provided using the methods described in Combustion
Air and Ventilation for Appliances Located in Confined Spaces.
Combustion Air and Ventilation
for Appliances Located in
Confined Spaces
Confined Space is a space whose volume is less than 50 cubic feet per
1,000 Btu per hour of the aggregate input rating of all appliances
installed in that space.
a. ALL AIR FROM INSIDE BUILDINGS:
(See Page 8 Figure 1, and Figure 5 below)
The confined space shall be provided with two permanent open-
ings communicating directly with an additional room(s) of suffi-
cient volume so that the combined volume of all spaces meets the
criteria for an unconfined space. The total input of all gas utiliza-
tion equipment installed in the combined space shall be considered
in making this determination. Each opening shall have a minimum
free areaof one square inch per 1,000 BTU per hour of the total
input rating of all gas utilization equipment in the confined space,
but not less than 100 square inches. One opening shall commence
within 12 inches of the top and one commencing within 12 inches
of the bottom of the enclosure.
Figure 5 ]
b. ALL AIR FROM OUTDOORS:
(see Figures 6-8)
The confined space shall be provided with two permanent open-
ings, one commencing within 12 inches of the top and one com-
mencing within 12 inches from the bottom of the enclosure.
The openings shaft communicate directly, or by ducts, with the
outdoors or spaces (crawl or attic) that freely communicate with
the outdoors.
Figure 6 ]
1. When directly communicating with the outdoors, each opening
shall have a minimum free area of I square inch per 4,000 BTU
_serhour of total input rating of all equipment in the endosure.
ee Figure 6.)
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 of total input rating of all equipment in
the enclosure. (See Figure 7.)
Figure 7 1
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LOU_
WA_R
....
,
,
,
,
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3. When communicating with the outdoors through horizontal
ducts, each openingshall have a minimum free area of 1 square
inch per 2,000 BTU per hour of total input rating of all equip-
ment in the enclosure.(See Figure8.)
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 mini-
mum short side dimension of rectangularair ducts shall not be
less than 3 inches. (SeeFigure 8.)
5. Louvers and Grilles: In calculating free area, consideration shall be
given to the blocking effect of louvers, grilles or screens protect-
ing openings. Screens used shall not be smaller than ¼ inch mesh.
If the free area through a design of louver or grille is known, it
should be used in calculating the size opening requiredto provide
the free area specified. If the design and free areais 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 fixed in the open position or inter-
locked with the equipment so that they are opened automatically
during equipment operation.
6. Special Conditions
Created by Mechanical Exhausting
or
Fireplaces:Operation of exhaust fans, ventilation systems, clothes
dryers or fireplaces may create conditions requiringspecial atten-
tion to avoidunsatisfactory operation of installed gas utilization
equipment.
11
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