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Air openings to combustion area must not be obstructed. By following the instructions below,
adequate combustion air can be maintained.
COMBUSTION AIR REQUIREMENTS
(Minimum Square Inches Requirement)
Unconfined Area*
Inside
Model
Combustion Air
Combustion Air
No.
1 Sq. In./1000
1 Sq. In./5000
Btu/Hr.
(Fig. #3)
15B045
100
15B070
100
15B096
100
15B120
125
15B145
150
15B175
175
15B195
200
15B245
250
15B295
300
* A space whose volume is not less than 50 cubic feet per 1000 BTU per 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 per hour of all
appliances installed in that space (cubic feet of space = height x width x length)
Ventilation of the boiler room must be adequate to provide
1.
sufficient air to properly support combustion per the latest
revision of the National Fuel Gas Code, ANSI Z223.1.
CHIMNEY OR
TYPE B VENT PIPE
When a boiler is located in an unconfined space in a
2.
building or conventional construction frame, masonry or
metal building, infiltration normally is adequate to provide
air for combustion and ventilation. However, if the equip-
ment is located in a building of tight construction (See the
National Fuel Gas Code, ANSI Z223.1 latest revision), the
boiler area should be considered as a confined space.
VENTILATION & COMBUSTION AIR
Confined Area**
Outside
Outside Combustion Air
Vertical Ducts
Horizontal Ducts
Btu/Hr.
1 Sq. In./4000
(Fig. #4)
BTU/Hr.
10
13
15
19
20
25
25
32
30
38
35
44
40
50
50
63
60
75
Figure #1
WARNING
!
In this case air for combustion and ventilation shall be
provided according to Step 5. If there is any doubt, install
air supply provisions in accordance with the latest revision
of the National Fuel Gas Code.
When a boiler is installed in an unconfined space in a
3.
building of tight construction, air for combustion and ven-
tilation must be obtained from outdoors or from spaces
1 Sq. In./2000
BTU/Hr.
freely communicating with the outdoors. A permanent
25
opening or openings having a total free area of not less
38
than 1 square inch per 5000 Btu per hour of total input
rating of all appliances shall be provided. Ducts may be
50
63
used to convey makeup air from the outdoors and shall
75
have the same cross-sectional area of the openings to
which they are connected.
88
When air for combustion and ventilation is from inside
4.
100
buildings, the confined space shall be provided with two
125
permanent openings, one starting 12 inches from the
150
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 1000 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 directly with other spaces of sufficient
volume so that the combined volume of all spaces meets
the criteria for an unconfined space. (Figure #1)
When the boiler is installed in a confined space and all air
5.
is provided from the outdoors the confined space shall be
provided with one or two permanent openings according
to methods A or B. When ducts are used, they shall be
of the same cross sectional area as the free area of the
area of the openings to which they connect. The minimum
dimension of rectangular air ducts shall be not less than 3
x 3 inches or 9 square inches.
A.
When installing two openings, one must commence with-
in 12 inches from the top and the other 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. One of the following methods must be used to
provide adequate air for ventilation and combustion.
5
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