All Air From Outdoors; Louvers And Grilles - Whirlpool Gas Water Heater High Efficiency Atmospheric Vent Installation Instructions And Use & Care Manual

All Air from Outdoors

Outdoor fresh air can be provided to a confined area either
directly or by the use of vertical and horizontal ducts. The
fresh air can be taken from the outdoors or from crawl or
attic spaces that freely communicate with the outdoors.
Attic or crawl spaces cannot be closed and must be
properly ventilated to the outside.
Ductwork must be of the same cross-sectional area as
the free area of the opening to which they connect. The
minimum dimension of rectangular air ducts cannot be less
than three inches.
The size of each of the two openings is determined by the
method in which the air is to be provided. Refer to Table
4 to calculate the minimum free area for each opening.
Figures 6, 7, 8A and 8B are typical examples of each
method.

Louvers and Grilles

In calculating free area for ventilation and combustion
air supply openings, consideration must be given to the
blocking effect of protection louvers, grilles, and screens.
These devices can reduce airflow, which in turn may
require larger openings to achieve the required minimum
free area. Screens must not be smaller than 1/4" mesh. If
the free area through a particular design of louver or grille
is known, it should be used in calculating the specified free
area of the opening. If the design and free area are not
known, it can be assumed that most wood louvers will allow
20 - 25% of free area while metal louvers and grilles will
allow 60 - 75% of free area.
Louvers and grilles must be locked open or interconnected
with the equipment so that they are opened automatically
during equipment operation.
Keep louvers and grilles clean and free of debris or other
obstructions.
Table 4
Minimum Free Area of Permanent Openings for Ventilation and
Combustion Air Supply - All Air from Outdoors Only.
Based on the total BTUH input rating for all gas utilizing equipment
within the confined space.
Minimum Free Area
Opening
Source
Direct to 1 Square inch per 4000
outdoors
Vertical ducts
1 Square inch per 4000
Horizontal ducts 1 Square inch per 2000
Example: A water heater with an input rate of 50,000 BTUH using
horizontal ducts would require each opening to have a minimum
free area of 25 square inches.
Minimum free area = 50,000 BTUH x 1 sq. in. / 2000 BTUH = 25
Sq. Inches.
These openings connect directly with the outdoors
*
through a ventilated attic, a ventilated crawl space, or
through an outside wall.
Consult the local codes of your area for specific ventilation and
combustion air requirements.
Reference
Per Opening
Drawing
(sq. in.)
Figure 6
BTUH
Figure 7
BTUH
Figure 8
BTUH
Confined Confined
Space Space
Alternate Alternate
Air Inlet Air Inlet
1 sq. inch per 1 sq. inch per
4000 BTUH 4000 BTUH
Figure 6 Figure 6
All Air from Outdoors; Inlet Air from Ventilated All Air from Outdoors; Inlet Air from Ventilated
Crawl Space/Outlet Air to Ventilated Attic Crawl Space/Outlet Air to Ventilated Attic
Confined Confined
Space Space
Figure 7 Figure 7
All Air from Outdoors All Air from Outdoors
Through Ventilated Attic Through Ventilated Attic
Confined Confined
Space Space
Figure Figure 8 8A
All Air from Outdoors All Air from Outdoors
Using Horizontal Ducts Using Horizontal Ducts
9
Gable vent Gable vent
to outdoors to outdoors
Install above Install above
insulation insulation
Outlet Outlet
air to attic air to attic
1 Sq. inch per 1 Sq. inch per
4000 BTUH 4000 BTUH
Inlet air Inlet air
from the from the
crawl crawl
space space
Open Open
Foundation Foundation
Vent Vent
Gable vent Gable vent
to outdoors to outdoors
Install above Install above
insulation insulation
Outlet air Outlet air
to attic to attic
1 Sq. inch per 1 Sq. inch per
4000 BTUH 4000 BTUH
Inlet air duct Inlet air duct
1 sq. inch per 1 sq. inch per
4000 BTUH 4000 BTUH
12" maximum 12" maximum
1 sq. inch 1 sq. inch
per per
2000 BTUH 2000 BTUH
Outlet Outlet
Outdoor Outdoor
Air Ducts Air Ducts
Inlet Inlet
1 sq. Inch 1 sq. Inch
per per
2000 BTUH 2000 BTUH