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9
Confined Space Installation
NOTE: A confined space is defined as an area with less than 50
cubic feet (1.4
3
M)per 1,000 BTUH (2.33 cm
2
/kW) input rating for
all gas appliances installed in the area.
Requirements
1. Provide the space with sufficient air for proper combustion
and ventilation of f lue gases using horizontal or vertical
ducts or openings.
2. Fig. 6 illustrates how to provide combustion and ventilation
air. A minimum of two permanent openings, one inlet and
one outlet, are required.
a. One opening MUST commence within 12″ (304.8mm)
of the floor and the second opening MUST commence
within 12″ (304.8mm) of the ceiling.
b. Size openings and ducts per Table 1.
c. Horizontal duct openings require 1 square inch of free
area per 2,000 BTUH (11 cm
2
/kW) of combined input
for all gas appliances in the space (see Table 1).
d. Vertical duct openings or openings directly
communicating with the outdoors require 1 square inch
of free area per 4,000 BTUH (5.5 cm
2
/kW) for
combined input of all gas appliances in the space (see
Table 1).
Minimum One Inlet and One Outlet Air Supply is Required
May be in any Combination Shown
Inlet Air Opening Must be Within12″of floor
Outlet Air Opening Must be Within12″ of ceiling
(1) 1 Square Inch per 4000 BTUH
(2) 1 Square Inch per 2000 BTUH
This installation NOT approved in Canada
Gas Vent
Gable Vent
Ventilated Attic
Top Above Insulation
Alternate Inlet Air (1)
Ventilated Crawl Space
Outlet Air (1)
Soffit Vent
Outlet
Air (1)
Inlet
Air (1)
Outlet
Air (2)
Inlet
Air (2)
Gas Vent
Inlet
Air (2)
Soffit Vent
Gas Vent
Gable Vent
Ventilated Attic
Top Above Insulation
Inlet
Air (1)
OutletAir (1)
alternate Inlet Air (1)
A07704
Fig. 6 -- Outside Air
(This is ONLY a guide. Subject to codes of country having jurisdiction).
3. One opening MUST be within 12″ (304.8mm) of the floor
and the second opening within 12″ (304.8mm) of the
ceiling.
a. 1 sq. in of free area per 3,000 BTUH (7 cm
2
/kW) for
combined input of all gas appliances in the space (see
Table 1)and
b. not less than the sum of the areas of all vent connectors
in the space.
The opening shall commence within 12″ (304.8mm) of the top of
the enclosure. Appliances shall have c learances of at least 1″
(25.4mm) from the sides and back and 6″ (152.4mm) from the
front. 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 communicate with the
outdoors.
4. Size openings and ducts per Table 1.
a. Indoor openings that comply with the Indoor
Combustion Air Method below and
b. Outdoor openings located as required in the Outdoor
Combustion Air Method above and
c. Outdoor openings sized as follows.
(1.) Calculate the Ratio of all Indoor Space volume
divided by required volume for Indoor
Combustion Air Method.
(2.) Outdoor opening size reduction Factor is 1 minus
the Ratio in 1) above.
(3.) Minimum size of Outdoor openings shall be the
size required in Outdoor Combustion Air Method
above multiplied by reduction Factor.
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
require 1 square inch of free area per 4,000 BTUH (5.5
cm
2
/kW) for combined input of all gas appliances in area
(see Table 1).
58HDV