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Page 8
SECTION 2 Venting and
Combustion Air
WARNING
For indoor installations, as an additional
measure of safety, the manufacturer strongly
recommends installation of suitable Carbon
Monoxide detectors in the vicinity of this
appliance and in any adjacent occupied spaces.
AVERTISSEMENT
Pour des installations intérieures, el fabricante
recommande fortement, comme mesure
de sécurité supplémentaire, l'installation de
détecteurs de monoxyde de carbone adaptés
dans le voisinage de l'appareil et dans chacune
des pièces habitées adjacentes.
2.A Combustion Air
These boilers and water heaters must have
provisions for combustion and ventilation air in
accordance with the applicable sections addressing
requirements for air for combustion and ventilation of
the National Fuel Gas Code, ANSI Z223.1. In Canada,
the applicable sections of the Natural Gas and Propane
Installation Code (CSA B149.1) must be followed. In
all cases any and all applicable local installation codes
must also be followed.
This appliance may receive combustion air from
the space in which it is installed, or it can be ducted
directly to the unit from the outside. Proper ventilation
air must be provided in either case.
2.A.1 Combustion Air From Room
In the United States, the most common
requirements specify that the space shall communicate
with the outdoors in accordance with method 1 or 2,
which follow. Where ducts are used, they shall be of
the same cross-sectional area as the free area of the
openings to which they connect.
Method 1: Two permanent openings, one
commencing within 12 inches (30 cm) of the top
and one commencing within 12 inches (30 cm) of
the bottom, of the enclosure shall be provided. The
openings shall communicate directly, or by ducts,
with the outdoors or spaces that freely communicate
with the outdoors. When directly communicating
with the outdoors, or when communicating to the
outdoors through vertical ducts, each opening shall
have a minimum free area of 1 square inch per 4000
Btu/hr (5.5 square cm/kW) of total input rating of all
equipment in the enclosure. When communicating to
the outdoors through horizontal ducts, each opening
shall have a minimum free area of not less than
1 square inch per 2000 Btu/hr (11 square cm/kW) of
total input rating of all equipment in the enclosure.
Table 1
shows data for this sizing method, for each
LAARS Heating Systems
boiler or water heater.
Method 2: One permanent opening, commencing
within 12 inches (30 cm) of the top of the enclosure,
shall be permitted. The opening shall directly
communicate with the outdoors or shall communicate
through a vertical or horizontal duct to the outdoors
or spaces that directly communicate with the outdoors
and shall have a minimum free area of 1 square inch
per 3000 Btu/hr (7 square cm/kW) of the total input
rating of all equipment located in the enclosure. This
opening must not be less than the sum of the areas of
all vent connectors in the confined space.
Other methods of introducing combustion and
ventilation air are acceptable, providing they conform
to the requirements in the applicable codes listed
above.
In Canada, consult local building and safety
codes or, in absence of such requirements, follow CSA
B149.1, the Natural Gas and Propane Installation Code.
Boiler
Model
Square inches
200
300
400
*Net Free Area in Square Inches / Square cm
Area indicated is for one of two openings; one at floor level
and one at the ceiling, so the total net free area could be
double the figures indicated.
This chart is for use when communicating directly with the
outdoors. For special conditions and alternate methods, refer
to the latest edition of ANSI Z223.1.
Note: Check with louver manufacturers for net free area of
louvers. Correct for screen resistance to the net free area
if a screen is installed. Check all local codes applicable to
combustion air.
Table 3.
Combustion Air Openings.
Figure 3. Combustion Air and Vent Through Roof.
Each Opening*
Square cm
50
323
75
484
100
645
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