6
VENTILATION & COMBUSTION AIR
COMBUSTION AIR REQUIREMENTS
(Minimum Square Inches Requirement)
Model
No.
Unconned Area* Conned Area**
Inside
Combustion Air Outside
Combustion Air Outside Combustion Air
1 Sq. In./1000
Btu/Hr.
(Fig. #3)
1 Sq. In./5000
Btu/Hr.
(Fig. #4)
Vertical Ducts
1 Sq. In./4000
BTU/Hr.
Horizontal Ducts
1 Sq. In./2000
BTU/Hr.
15B045 100 10 13 25
15B070 100 15 19 38
15B096 100 20 25 50
15B120 125 25 32 63
15B145 150 30 38 75
15B175 175 35 44 88
15B195 200 40 50 100
15B245 250 50 63 125
15B295 300 60 75 150
* 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)
Air openings to combustion area must not be obstructed. By following the instructions below,
adequate combustion air can be maintained.
WARNING
!
Ventilation of the boiler room must be adequate to provide
1.
sufcient air to properly support combustion per the latest
revision of the National Fuel Gas Code, ANSI Z223.1.
Figure #1
CHIMNEY OR
TYPE B VENT PIPE
When a boiler is located in an unconned space in a
2.
building or conventional construction frame, masonry or
metal building, inltration 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 conned space.
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 unconned space in a
3.
building of tight construction, air for combustion and ven-
tilation 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 5000 Btu per hour of total input
rating of all appliances shall be provided. Ducts may be
used to convey makeup 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 ventilation is from inside
4.
buildings, the conned 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 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 sufcient
volume so that the combined volume of all spaces meets
the criteria for an unconned space. (Figure #1)
When the boiler is installed in a conned space and all air
5.
is provided from the outdoors the conned 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.
When installing two openings, one must commence with-A. 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.
