Combustion air requirements
Supply combustion air to the units as per the National
Fuel Gas Code, ANSI Z223.1 and in Canada, in
accordance with NSCNGPIC.
• Provide two permanent openings to allow circulation
of combustion air.
• Make each opening 180 square inches if they pro-
vide indoor air, and 100 square inches for outdoor
• If the unit is installed in a mechanical closet, provide
a 24" (600mm) clearance in front of the unit to the
• If combustion air will be provided through a duct, size
the duct to provide 60 cubic feet of fresh air per
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