Combustion and Ventilation AIR

When installed, this gas appliance must be provided with fresh air for combustion, ventilation, and dilution of hot flue gases. The minimum required volume of the area where the appliance is installed should be 50 cubic feet per 1,000 btu/hr.

If installed in an area of the home that is considered an unconfined space, the natural infiltration of air around windows and doors will be adequate. If the area is considered a confined space (less than 50 cubic feet per thousand btu), fresh air can be supplied by providing two permanent openings into adjoining rooms. Each opening shall have a minimum free area of one square inch per 1,000 btu per hour of the total input rating of all gas appliances in the confined space, but not less than 100 square inches. One of the openings shall be within 12 inches of the ceiling and one within 12 inches of the floor. See Figure A.

If the home is of unusually tight construction (new and remodeled homes), free air must be supplied through opening(s) to the outdoors. This can be accomplished by providing 2 permanent openings, one commencing within 12 inches of the ceiling and one within 12 inches of the floor. These openings shall communicate directly with the outdoors, or spaces that communicate freely with the outdoors, such as a ventilated attic and crawl space through galvanized or equivalent corrosion-resistant ducts. Exception: unobstructed stud and joist spaces are acceptable ducts provided that not more than one fire block is removed. Special provisions must be taken to insure that these stud and joist spaces cannot be blocked with insulation or other objects. Each of these openings using vertical ducts shall have a minimum free area of one square inch per 4,000 btu/hr of total input rating of all gas appliances. See Figure B and C. If horizontal ducts are used, the minimum free area shall be one square inch per 2,000 btu/hr of total input rating of all gas appliances.

Fresh make-up air can also be provided through a duct to one permanent opening commencing within 12 inches of the ceiling. The minimum free area of this opening shall be one square inch per 3,000 btu/hr of the total input rating of all gas appliances but not less than the sum of the areas of all vent connectors in the space. See Figure D.

When calculating the amount of fresh air needed you must include make-up air requirements for the operation of exhaust fans, kitchen ventilation systems, clothes dryers, and fireplaces.

Additional information can be found in the latest edition of ANSI Z223.1 (National Fuel Gas Code).

ALL COMBUSTION AIR FROM ADJACENT INDOOR SPACES THROUGH INDOOR COMBUSTION AIR OPENINGS

UL Listed Vent Cap

UL Listed Gas Vent

Opening

FIGURE A

ALL COMBUSTION AIR FROM OUTDOORS. INLET AIR FROM VENTILATED CRAWL SPACE AND OUTLET AIR TO VENTILATED ATTIC

UL Listed Vent Cap

UL Listed Gas Vent

Ventilation Louvers (each end of attic)

Outlet Air

Inlet Air

Ventilation

louvers for unheated crawl space

FIGURE B

ALL COMBUSTION AIR FROM OUTDOORS

THROUGH VENTILATED ATTIC

UL Listed Vent Cap

UL Listed Gas Vent

Ventilation Louvers (each end of attic)

	Inlet	Outlet Air
	Grille	Outlet Air
	Grille
	Inlet	Inlet Air Duct (Ends 1 Ft.
	Inlet	[300 mm] above floor)
	Grille

ALL COMBUSTION AIR FROM OUTDOORS

THROUGH SINGLE COMBUSTION AIR OPENING

UL Listed Vent Cap

UL Listed Gas Vent

Opening

Alternate opening location

FIGURE C

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Louisville Tin and Stove VC202A-H, VCR702A-H, VCR701A-H, VCR352A-H Combustion and Ventilation AIR