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Air openings to combustion area must not be obstructed. By following the instructions below,
adequate combustion air can be maintained.
BTU/hr
Combustion Air 1 Sq.
Input
In./5000 BTU/hr
107,800
140,000
196,000
* A space whose volume is not less than 50 cubic feet per 1000 BTU/Hour of all appliances installed in that space (cubic feet of space = height x width x length)
** A space whose volume is less than 50 cubic feet per 1000 BTU/Hour of all appliances installed in that space (cubic feet of space = height x width x length)
Ventilation of boiler room must be adequate enough to
1.
provide sufficient air to properly support combustion
and venting.
When the boiler is located in an unconfined space in a
2.
building of conventional construction frame, masonry
or metal, infiltration normally is adequate to provide
air for combustion and ventilation. however, in any
building which has been altered to conserve energy
or to minimize infiltration, the boiler area should
be considered as a confined space. If there is any
doubt, install air supply provisions for combustion
and ventilation in accordance with section 5.3, Air
for Combustion and Ventilation, of the NFPA 54 1988
code, the recommendations that follow, or applicable
provisions of the local building codes.
When the boiler is installed in an unconfined space,
3.
in a building of unusually tight construction, air for
combustion and room ventilation must be obtained
from outdoors or from spaces freely communicating
with the outdoors. A permanent opening or openings
having a total free area of not less than 1 square inch
per 5,000 BTU per hour of total input rating of all
appliances shall be provided. Ducts may be used to
convey make-up air from the outdoors and shall have
the same cross-sectional area of the openings to which
they are connected.
When air for combustion and room ventilation is from
4.
inside buildings, the confined space shall be provided
with two permanent openings, one starting 12 inches
from the top and one 12 inches from the bottom of the
enclosed space. Each opening shall have a minimum
free area of 1 square inch per 1,000 BTU per hour of
the total input rating of all appliances in the enclosed
space, but must not be less than 100 square inches.
These openings must freely communicate with the
interior areas having adequate infiltration from the
outside. (Figure #3)
VENTILATION AND COMBUSTION AIR
COMBUSTION AIR REQUIREMENTS
(Minimum Opening Requirement)
Unconfined Area*
Outside
Combustion Air 1 Sq.
In./1000 BTU/hr
(Min. 100 Sq. In.)
(Step 4)
22
28
40
WARNING
Inside
Vertical Ducts 1 Sq.
In./4000 BTU/hr
(Figures 2 & 3)
108
140
196
When the boiler is installed in a confined space and
5.
all air is provided from the outdoors, the confined
space shall be provided with two permanent openings,
one commencing within 12 inches from the top and
one commencing 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. One of the
following methods must be used to provide adequate
air for ventilation and combustion.
A.
When directly communicating with the outdoors,
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. (Figure
#4)
B.
When communicating with the outdoors by means
of vertical ducts, each opening shall have a mini-
mum free area 1 square inch per 4,000 BTU per
hour of total input rating of all appliances in the
enclosed space. (Figure #5)
Figure #3
L TYPE VENT PIPE
BASEBOARD
VENT PIPE
5
Confined Area**
Outside Combustion Air
horizontal Ducts 1 Sq.
In./2000 BTU/hr
27
35
49
CHIMNEY
OR
12"
12"
(Figure 4)
54
70
98
VENTS
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