3.
4.
Figure 6 illustrate how to provide combustion and ventila-
tion air. A minimum of two permanent openings, one inlet
and one outlet, are required.
One opening MUST be within 12" of the floor and the se-
cond opening within 12" of the ceiling.
Size openings and ducts per Table 1.
5. Horizontal duct openings require 1" square offree area per
2,000 BTUH of combined input for all gas appliances in
area (see Table 1).
6. Vertical duct openings or openings directly to outside re-
quire 1" square of free area per 4,000 BTUH for combined
input of all gas appliances in area (see Table 1).
Outside Air (This is ONLY a guide. Subject to codes of country having jurisdiction.)
ThisinstallationNOTapprovedinCanada
GableVent_b.J
- OptionalInlet Air (t)
I II I -- I
_Air (t)
wate_
SoffitVent
Gable Vent
Air (t)
Inlet
Air (t]
Soffit Vent
MinimumOneInlet and One OutletAir Supply isRequired
May beinand CombinationShown
InletAir OpeningMust be Within12"of floor
OutletAir OpeningMustbeWithin12" of ceiling
(t) t SquareInch per4000 BTUH
(2)t SquareInch per2000 BTUH
Inlet
Air(t)
Inlet
Air (2)
MinimumFreeArea Requiredfor Each Opening
BTUH
input HorizontalDuct
Rating (2,000BTUH)
50,000 25 sq.in.
75,000 37.5sq. in.
100,000 50 sq.in.
125,000 62.5sq. in.
150,000 75 sq. in.
VerticalDuct oropenings Round
to outside Duct
(4,000BTUH) (4,000
BTUH)
12.5 sq.in. 4"
18.75sq. in. 5"
25 sq. in. 6"
31.25sq, in. 7"
37.5 sq. in. 7"
EXAMPLE: Determining Free Area
Appliance 1 Appliance 2 Total Input
100,000 + 30,000 = (130,000 + 4,000) = 32.5 Sq. In. Vertical
Appliance 1 Appliance 2 Total Input
100,000 + 30,000 = (130,000 + 2,000) = 65 Sq. In. Horizontal
One permanent opening, commencing within 12" of the top of the
enclosure, shall be permitted where the equipment has clear-
ances of at least 1" from the sides and back and 6" from the front
of the appliance. The opening shall directly communicate with the
outdoors or shall communicate through a vertical or horizontal
duct to the outdoors or spaces (crawl or attic) that freely communi-
cate with the outdoors, and shall have a minimum free area of:
• 1 sq. in per 3000 Btu per hr. of the total input rating of all
equipment located in the enclosure, and
• Not less than the sum of the areas of all vent connectors
in the confined space.
UnconfinedSpaceInstallation
Poison carbon monoxide gas Hazard,
Most homes will require additional air.
An unconfined space or homes with tight
construction may not have adequate air
infiltration for proper combustion and ventilation
of flue gases.
Failure to supply additional air by means of
ventilation grilles or ducts could result in death
and/or personal injury.
BTUH Input
Rating
50,000
78,000
114,000
155,000
An unconfined space is defined as an area having a minimum vol-
ume of 50 cubic feet per 1,000 Btuh total input rating for all gas
appliances in area. Refer to Table 2 for minimum area required.
I Unconfined Space
Minimum Area in Square Feet
Minimum Area in Square Feet
312
490
712
968
EXAMPLE: NOTE: Square feet is based on 8 foot ceilings,
28,000BTUH X 50CubicFt. = 1,400 = 175Sq. Ft.
1,000 8' Ceiling Height
44001 101004
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