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2.
Figure 5 illustrate how to provide combustion and ventila-
tion air. A minimum of two permanent openings, one inlet
and one outlet, are required.
Outside Air (This is ONLY a guide. Subject to codes of country having jurisdiction.)
Figure 5
Gable Vent
Gas Vent
Ventilated Attic
Top Above Insulation
Outlet Air (1)
Ventilated Crawl Space
alternate Inlet Air (1)
4.
Size openings and ducts per Table 1.
5.
Horizontal duct openings require 1 square inch of free 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 inch of free area per 4,000 BTUH for com-
bined input of all gas appliances in area (see Table 1).
Table 1
Minimum Free Area Required for Each Opening
BTUH
BTUH
Input
Horizontal Duct
Rating
(2,000 BTUH)
50,000
25 sq. in.
75,000
37.5 sq. in.
100,000
50 sq. in.
62.5 sq. in.
125,000
150,000
75 sq. in.
EXAMPLE:
Determining Free Area
Appliance 1 Appliance 2
100,000 + 30,000 = (130,000 ¸ 4,000) = 32.5 Sq. In. Vertical
Appliance 1 Appliance 2
100,000 + 30,000 = (130,000 ¸ 2,000) = 65 Sq. In. Horizontal
One permanent opening, commencing within 12² of the top of the
enclosure, shall be permitted where the equipment has clearances
of at least 1² from the sides and back and 6² from the front of the
appliance. The opening shall directly communicate with the out-
doors or shall communicate through a vertical or horizontal duct to
the outdoors or spaces (crawl or attic) that freely communicate 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.
8
This installation NOT approved in Canada
alternate Inlet Air (1)
Gas Vent
Soffit Vent
Inlet
Air (1)
Free Area
Vertical Duct or openings
Round Duct
to outside (4,000 BTUH)
(4,000 BTUH)
12.5 sq. in.
4²
18.75 sq. in.
5²
25 sq. in.
6²
31.25 sq. in.
7²
37.5 sq. in.
7²
Total Input
Total Input
3.
One opening MUST be within 12² of the floor and the second
opening within 12² of the ceiling.
Gable Vent
Ventilated Attic
Top Above Insulation
Soffit Vent
OutletAir (1)
Inlet
Air (2)
Unconfined Space Installation
!
CARBON MONOXIDE POISONING HAZARD
Failure to supply additional air by means of ventilation
grilles or ducts could result in death and/or personal
injury.
An unconfined space or homes with tight construction
may not have adequate air infiltration for proper
combustion and ventilation of flue gases.
Most homes will require additional air.
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 ap-
pliances in area. Refer to Table 2 for minimum area required.
Table 2
BTUH Input
Rating
50,000
78,000
114,000
155,000
EXAMPLE: NOTE: Square feet is based on 8 foot ceilings.
28,000 BTUH X 50 Cubic Ft. =
1,000
NOTE: Refer to definitions in section titled Unusually Tight
Construction. If any one of the conditions apply, the space MUST
be considered confined space regardless of size.
1.
Adjoining rooms can be considered part of an unconfined
area if there are openings without doors between rooms.
2.
An attic or crawl space may be considered an unconfined
space provided there are adequate ventilation openings di-
rectly to outdoors. Openings MUST remain open and NOT
have any means of being closed off. Ventilation openings to
outdoors MUST be at least 1² square of free area per 4,000
BTUH of total input rating for all gas appliances in area.
Gas Vent
Outlet
Air (1)
Inlet
Air (1)
Minimum One Inlet and One Outlet Air Supply is Required
May be in any Combination Shown
Inlet Air Opening Must be Within12² of floor
Outlet Air Opening Must be Within12² of ceiling
(1) 1 Square Inch per 4000 BTUH
(2) 1 Square Inch per 2000 BTUH
Unconfined Space
Minimum Area in Square Feet
Minimum Area in Square Feet
312
490
712
968
1,400
8¢ Ceiling Height
Outlet
Air (2)
Inlet
Air (2)
= 175 Sq. Ft.
440 01 1020 02
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