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Installation
Instructions
(cont'd)
Combustion
Air and Ventilation
for Appliances
Located
in
Unconfined
Spaces
Unconfined
Space is a space whose volume 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
are installed,
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 Bru 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
openings
communicating
directly with an additional
room(s)
of 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
free 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.
1. When direcdy communicating with the outdoors, each open-
ing shall have a minimum free area of I square inch per 4,000
BTU per hour of total input rating 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
s,q[uareinch per 4,000 BTU per hour of total input rating of
all equipment in the enclosure. (See Figure 4.)
Figure 4 ]
3. When communicating
with the outdoors
through
hOrizontal
ducts,
each opening
shall have a minimum
free area of 1
s_uare inch per 2,000 BTU per hour of total input rating of
all equipment
in the enclosure. (See Figure 5.)
Figure 2 ]
b. ALL AIR FROM
OUTDOORS:
(see Figures 3-5)
The confined
space shall be provided
with 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 ]
Figure 5 ]
10
,
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.)
5.
Louvers and Grilles: In calculating
free area, consideration
shall be given to the blocking
effecr 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
opening
required
to provide
the free area specified.
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 fixed in the open position or interlocked
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
requiring
special attention to avoid unsatisfactory
operation of installed
gas utilization
equipment.
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