Ventilation & Combustion Air - Columbia MCB50 Installation, Operation & Maintanance Manual

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)
50 100
75 100
100 100
125 125
150 150
175 175
200 200
250 250
300 300
* 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)
1. Ventilation of the boiler room must be adequate to provide
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
2. When a boiler is located in an unconfined space in a
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.
3. When a boiler is installed in an unconfined space in a
building of tight construction, air for combustion and ven-
1 Sq. In./2000
tilation must be obtained from outdoors or from spaces
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
50
rating of all appliances shall be provided. Ducts may be
63
used to convey makeup air from the outdoors and shall
have the same cross-sectional area of the openings to
75
which they are connected.
88
4. When air for combustion and ventilation is from inside
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)
5. When the boiler is installed in a confined space and all air
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