LAARS Mighty Stack MS-080 (Sizes 199, 300, 399) - Install and Operating Manual - Manual (Page 7)

Mighty Stack Page 7
Figure 2. Combustion Air and Vent Through Roof.
SECTION 2.
Venting and Combustion Air
WARNING
For indoor installations, as an additional measure
of safety, Laars 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, Laars
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.
2.1 Combustion Air
Mighty Stack 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.
A Mighty Stack 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.
2.1.1 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 3 shows data for this sizing method, for each
Mighty Stack model.
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.
Size
Each Opening*
Square inches Square cm
199 50 323
300 75 484
399 100 645
*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.