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Installation
Instructions
(cont'd)
Combustion
Air and Ventilation
for Appliances
Located in
Unconfined
Spaces
Uncunl_ed
Spac* is a space whose volum_ is not less than 50
cubic feet per 1,000 Btu per hour of the aggregate input rating
of all appliances installed in that space. Rooms communicating
directly with the space in which the appliances am installeff,
through openings not furnished 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, b.
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 9 Figure 1, and Figure 2 below)
The confined
space shall be provided
with two permanent
o_enings communicating
directly with an additional room(s)
or sufficient
volume
so that the combined
volume
of all
spaces meets the criteria for an unconfined
space. The total
input of all gas utilization
equipment
installed
in the com-
bined space shall be considered in making this determination.
Each opening shall have a minimum
flee area of 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.
b. ALL AIR FROM OUTDOORS:
(see Figures3-5)
The confined space shall be provided witl_ two permanent
openings, one commencing within 12 inches of the top and
one commencing within 12 inches 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.
Figure 3 ]
10
1. When directly communicating with the outdoors, each open-
ing shall have a minimum free area of 1 square inch per 4,000
BTU per hour of total input raring of all equipment in the
enclosure. (See Figure 3.)
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 ratin_of
all equ pment in the enclosure. (See Figure 4.)
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ot_1_1
OR OAS VEK'g
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tan OUTLET
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3. When communicating
with the outdoors
through
horizontal
ducts, each opening
shall have a minimum
free area of 1
_uare
inch per 2,000 BTU per hour of total input rating of
equipment
in the enclosure. (See Figure 5.)
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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. (See Figure 5.)
,
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 ¼ inch mesh. If the free area through a design of louver
or grille is known, it should be used in calculating
the size
o, p enin, g required
to .provide the free. area specified.
If the
aesLgn 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 fixed in the open position or interlocked with
the .equipment
so. that they are opened automatically during
eqmpment
operauon.
6. Special
Conditions
Created
by Mechanical
Exhausting
or
Fireplaces:
Operation
of exhaust
fans, ventilation
systems
domes
dryers or fireplaces may create conditions
requiring
special attention to avoid unsatisfactory operation of installed
gas utilization equipment.
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