Sears 153.33262 Manual De Usuario
18
12” Max.
Permanent
openings to
the outside or
additional
rooms within
the building
openings to
the outside or
additional
rooms within
the building
Closet
or other
confined
space
12” Max.
FIGURE 13.
All Air from the Building
When additional air is to be provided to the confined area
from additional room(s) within the building, the total volume of
the room(s) must be of sufficient size to properly provide the
necessary amount of fresh air to the water heater and other
gas utilization equipment in the area. If you are unsure that the
structure meets this requirement, contact your local gas utility
company or other qualified agency for a safety inspection.
Each of the two openings shall have a minimum free area of 1
square inch per 1,000 BTUH of the total input rating of all gas
utilization equipment in the confined area, but not less than 100
square inches (Figure 14).
from additional room(s) within the building, the total volume of
the room(s) must be of sufficient size to properly provide the
necessary amount of fresh air to the water heater and other
gas utilization equipment in the area. If you are unsure that the
structure meets this requirement, contact your local gas utility
company or other qualified agency for a safety inspection.
Each of the two openings shall have a minimum free area of 1
square inch per 1,000 BTUH of the total input rating of all gas
utilization equipment in the confined area, but not less than 100
square inches (Figure 14).
FIGURE 14.
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.
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.
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 15,
16, 17 and 18 are typical examples of each method.
method in which the air is to be provided. Refer to Table 4 to
calculate the minimum free area for each opening. Figures 15,
16, 17 and 18 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.
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.
the equipment so that they are opened automatically during
equipment operation.
Keep louvers and grilles clean and free of debris or other
obstructions.
obstructions.
TABLE 4
Minimum Free Area of Permanent Openings for Ventilation and
Combustion Air Supply - All Air from Outdoors Only.
Based on total BTUH input rating for all utilizing equipment
Based on total BTUH input rating for all utilizing equipment
within the confi ned space.
Opening Source
Minimum Free Area
Per Opening (sq. in.)
Reference Drawing
*Direct to outdoors
1 sq. in, per 4000 BTUH
Figure 15
Vertical Ducts
1 sq. in, per 4000 BTUH
Figure 16
Horizontal Ducts
1 sq. in, per 2000 BTUH
Figure 17
Single Opening
1 sq. in, per 3000 BTUH
Figure 18
Example: A water heater with an input rating of 50,000 BTUH using
horizontal ducts would require each opening to have a minimum free
area of 25 square inches.
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. in.
*
These openings connect directly with the outdoors through a venti-
lated attic, a ventilated crawl space, or through an outside wall.
lated attic, a ventilated crawl space, or through an outside wall.
Consult the local codes of your area for specific ventilation and
combustion air requirements.
combustion air requirements.
Confined
Space
Space
Permanent
Openings
Openings
1 Square
inch/1000
BTUH
(min. 100
sq. in.)
inch/1000
BTUH
(min. 100
sq. in.)