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where:
I
= Input of appliances other than fan
other
assisted in Btu/hr
ACH = air change per hour (percent of the
volume of the space exchanged per
hour, expressed as a decimal)
For fan assisted appliances, calculate the required
volume of air using the following equation:
Required Volume
I
= Input of the fan assisted appliances in
fan
Btu/hr
Note: These calculations are not to be used for
infiltration rates greater than 0.60 ACH.
3. Indoor Air Opening Size and Location: Openings
connecting indoor spaces shall be sized and located
as follows:
a. Combining spaces on the same floor:
Provide two permanent openings communicating
with additional spaces that have a minimum free
2
area of 1 in
per 1000 Btu/hr (22 cm
of the total input rating of all gas fired equipment
but not less than 100 in
opening is to begin within 12 inches (305 mm)
from the top of the space and the other is to
begin within 12 inches (305 mm) from the floor.
The minimum dimension of either of these
openings shall be 3 inches (76 mm). See Figure
1.1 for an illustration of this arrangement.
Figure 1.1:
Air Openings – All Air from Indoors
on the Same Floor
b. Combining spaces on different floors:
Provide one or more permanent openings
communicating with additional spaces that have
a total minimum free area of 2 in
2
Btu/hr (44 cm
of all equipment. See Figure 1.2 for an
illustration of this arrangement.
⎛
15 ft
3
I
fan
⎜
=
fan
⎝
Btu
ACH
1000
/
hr
2
per 1000 W)
2
2
(645 cm
). One
2
per 1000
per 1000 W) of total input rating
⎝
⎜
⎛
Figure 1.2:
Air Openings – All Air from Indoors
on Different Floors
4. Outdoor Combustion Air: Outdoor combustion air is
to be provided through one or two permanent
openings. The minimum dimension of these air
openings is 3 inches (76 mm).
a. Two Permanent Opening Method: Provide
two permanent openings. One opening is to
begin within 12 inches (305 mm) of the top of
the space and the other is to begin within 12
inches (305 mm) of the floor. The openings are
to communicate directly or by ducts with the
outdoors or with spaces that freely communicate
with the outdoors. The size of the openings shall
be determined as follows:
i. Where communicating directly or through
vertical ducts with the outdoors each opening
shall have a minimum free area of 1 in
4000 Btu/hr (22 cm
input rating for all equipment in the space.
See Figure 1.3 for openings directly
communicating with the outdoors or Figure
1.4 for openings connected by ducts to the
outdoors.
Figure 1.3:
Air Openings – All Air Directly from
Outdoors
PREINSTALLATION
2
per
2
per 4000 W) of total
3
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