10
440 01 1024 01
Specifications are subject to change without notice
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
Outside Air (This is ONLY a guide. Subject to codes of country having jurisdiction.)
Figure 6
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)
c.
Horizontal duct openings require 1 square inch of free
area per 2,000 BTUH (1,100 mm
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 (550 mm
2
/kW) for combined
input of all gas appliances in the space
(
see
Table 1).
3. When one permanent outdoor opening is used, the opening
requires:
a.
1 sq. in of free area per 3,000 BTUH (700 mm
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
″
of the top of the
enclosure. Appliances shall have clearances of at least 1
″
from the
sides and back and 6
″
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. Combination of Indoor and Outdoor Air shall have:
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
.
Table 1
Free Area
BTUH
Input
Rating
Minimum Free Area Required for Each Opening or Duct to Outdoors
Two Horizontal Ducts
(sq. in./2,000 BTUH)
Single Opening
(sq. in./3,000 BTUH)
Two Vertical Ducts or Openings
(sq. in./4,000 BTUH)
Round Duct
(sq. in. /4,000 BTUH)
40,000
20 sq. in.
13.3 sq. in.
10.0 sq. in.
4
″
50,000
25 sq. in.
16.7 sq. in.
12.5 sq. in.
4
″
60,000
30 sq. in.
20 sq. in.
15.0 sq. in.
4
″
75,000
37.5 sq. in.
25 sq. in.
18.75 sq. in.
5
″
80,000
40 sq. in.
26.7 sq. in.
20.0 sq. in.
5
″
100,000
50 sq. in.
33.3 sq. in.
25 sq. in.
6
″
125,000
62.50 sq. in.
41.7 sq. in.
31.25 sq. in.
7
″
EXAMPLE:
Determining Free Area
Furnace
100,000
Furnace
100,000
+
+
Water Heater
30,000
Water Heater
30,000
=
=
Total Input
(130,000
÷
4,000)
Total Input
(130,000
÷
2,000)
=
32.5 Sq. In. Vertical
=
65 Sq. In. Horizontal