Installation, Operation & Maintenance Manual
E
coer
96%
A
F
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Gas Furnace
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E
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07-2021
Data subject to change
Air Supply Openings and Ducts
1.
An opening may be used in lieu of a duct to provide the outside air supply
to an appliance unless otherwise permitted by the authority having
jurisdiction. The opening shall be located within 12” (30.5 cm) horizontally
from the burner level of the appliance.
2.
The duct shall be either metal or a material meeting the class 1
requirements of CAN4-S110 Standard for Air Ducts.
3.
The duct shall be at least the same cross-sectional area as the free area of
the air supply inlet opening to which it connects.
4.
The duct shall terminate within 12 in (30.5 cm) above, and within 24 in
(61 cm) horizontally from, the burner level of the appliance having the
largest input.
5.
A square or rectangular shaped duct shall only be used when the required
free area of the supply opening is 9 in 2 (58.06 cm 2 ) or larger. When a
square or rectangular duct is used, its small dimension shall not be less than
3 in (7.6 cm).
6.
An air inlet supply from outdoors shall be equipped with a means to prevent
the direct entry of rain and wind. Such means shall not reduce the required
free area of the air supply opening.
7.
An air supply inlet opening from the outdoors shall be located not less than
12 in (30.5 cm) above the outside grade level.
Combustion Air Source from Outdoors
1.
Two permanent openings, one within 12 in (305 mm) of the top and
one within 12 in (305 mm) of the bottom of the con
fi
ned space, shall
communicate directly or by means of ducts with the outdoors, crawl spaces
or attic spaces.
2.
One permanent opening, commencing within 12 in (305 mm) of the top of
the enclosure shall be permitted where the equipment has clearances of
at least 1 in (25.4 mm) from the sides and back and 6 in (152.4 mm) from
the front of the appliance. The opening shall communicate directly with the
outdoors and shall have a minimum free area of:
a. 1 square inch per 3000 Btu per hour (734 mm2/kW) of the total
input rating of all equipment located in the enclosure.
b. Not less than the sum of all vent connectors in the con
fi
ned space.
3.
The duct shall be at least the same cross-sectional area as the free area of
the air supply inlet opening to which it connects.
4.
The blocking effects of louvers, grilles and screens must be given
consideration in calculating free area. If the free area of a speci
fi
c louver or
grille is not known, refer to Table 21 ,“Estimated Free Area” to estimate free
area.
Wood or Metal Louvers or Grilles
Wood 20-25%, Metal 60-70%
Screens
1/4” mesh or larger 100%
Table 12
Estimated Free Area
8.6.4 Ventilated Combustion Air
The ventilated attic space or a crawl space from which the combustion air is taken
must comply with the requirements speci
fi
ed in “
Combustion Air Source from
Outdoors
” in this instruction or in Section 7.4, Air for Combustion and Ventilation
of the National Fuel Gas Code, ANSI Z223.1 (latest edition). This type in stallation
requires two properly sized pipes. One brings combustion air from a properly
ventilated attic space or crawl space and a second pipe that extends from the
furnace vent connection (top right of unit) to the exterior of the building.
