Fresh Air Openings For Confined Spaces; Outdoor Air Through Two Openings; Outdoor Air Through One Opening - A.O. Smith BT-100-LP Instruction Manual

and free area are not known, it shall be assumed that
wood louvers will have 25% free area and metal louvers
and grilles will have 75% free area. Non motorized
louvers and grilles shall be fixed in the open position.

FRESH AIR OPENINGS FOR CONFINED SPACES

The following instructions shall be used to calculate the
size, number and placement of openings providing fresh
air for combustion, ventilation and dilution in confined
spaces. The illustrations shown in this section of the
manual are a reference for the openings that provide
fresh air into confined spaces only. Do not refer to these
illustrations for the purpose of vent installation. See
(page 19) for complete venting instructions.
Venting

OUTDOOR AIR THROUGH TWO OPENINGS

FIGURE 13. FRESH AIR FROM TWO OPENINGS
The confined space shall be provided with two permanent
openings, one commencing within 12 inches (300 mm)
of the top and one commencing within 12 inches (300
mm) of the bottom of the enclosure. The openings shall
communicate directly with the outdoors. See
Each opening shall have a minimum free area of 1
square inch per 4,000 Btu/hr (550 mm
aggregate input rating of all appliances installed in the
enclosure. Each opening shall not be less than 100
square inches (645 cm ).
2

OUTDOOR AIR THROUGH ONE OPENING

Alternatively a single permanent opening, commencing
within 12 inches (300 mm) of the top of the enclosure,
shall be provided. See
The water heater shall have clearances of at least 1 inch
(25 mm) from the sides and back and 6 inches (150 mm)
from the front of the appliance. The opening shall directly
communicate with the outdoors or shall communicate
through a vertical or horizontal duct to the outdoors or
spaces that freely communicate with the outdoors and
shall have a minimum free area of the following:
1. One square inch per 3000 Btu/hr (733 mm
2. Not less than the sum of the areas of all vent
.
Figure 13
per kW) of the
2
17
FIGURE 14. FRESH AIR FROM ONE OPENING
Figure 14
of the total input rating of all appliances located in the
enclosure, and
connectors in the space.
.
per kW)
2