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Supply combustion air to the units as per the National Fuel Gas Code, ANSI Z223.1-
latest edition and in Canada, in accordance with the Natural Gas and Propane Installa-
tion Code CSA B149.1-latest edition.
Combustion Air
Openings supplying indoor air
H
W
H
W
• Provide two permanent openings to allow
circulation of combustion air.
• A minimum free area of each openings
• If the unit is installed in a mechanical closet,
a minimum of permanent clearance of 4" or
more in front of the unit is required. A 24" or
more clearance is recommended in order to
facilitate maintenance and repair.
• If combustion air will be provided through a
duct, size the duct to provide 63 cubic feet of
fresh air per minute.
• If the unit is installed in a mobile home, outdoor
air must be supplied. The usage of the "-SV"
conversion kit is prohibited.
Indoor make up
air is provided
Outdoor make up air is provided
Direct or
Vertical ducts Horizontal ducts
180 in
2
20" (W) x 9" (H)
45 in
2
10" (W) x 4 1/2" (H)
90 in
2
20" (W) x 4 1/2" (H)
Provide adequate combustion air so as to not create negative pressure within the building.
