Combustion Air Requirements - TANKLESS EZ-101 User Manual

Combustion air requirements

Appliances located in unconfined spaces:
a) An unconfined space is one whose volume is greater than 50 cubic feet per 1000 Btu per hour
of the combined rating of all appliances installed in the space.
b) Installations in structures that have been tightly constructed (air infiltration rate of 0.40 ACH
or less) must be provided for combustion air per the National Fuel Gas Code. Consult a HVAC
specialist if your air infiltration rate is questionable.
Basic rules for Appliances located in confined spaces:
The confined space must be provided with two permanent openings, one commencing within 12
inches of the top and one commencing within 12 inches of the bottom of the enclosure. Each
opening must have a minimum free area of one square inch per:
. 1000 Btu/hr if all air is taken from inside the building.
. 2000 Btu/hr if all air is taken from the outside by horizontal ducts.
. 4000 Btu/hr if all air is taken from the outside by direct openings or vertical ducts. Or the
confined space must be provided with one permanent opening or duct that is within 12 inches of
the ceiling of the enclosure. This opening must have a minimum free area of one square inch per:
3000 Btu/hr if all air is taken from the outside by a direct opening or vertical duct.
Louvers, grills and screens have a blocking effect. If the effective free area is not known,
increase the sizes of your openings by 400% if your louvers are wood and by 135% if your
louvers are metal. Refer to the National Fuel Gas Code for complete information. In buildings of
tight construction all air should be taken from outside.