A.O. Smith Water Heater - Manual (Page 11)

COMBUSTION AIR & VENTILATION
AWARNING
Carbon Monoxide Warning
Water heater must be vented to outdoors.
Vent must be installed by a qualified technician using
the installation instructions.
Examples of a qualified technican include: gas
technicians, authorized gas company personal, and
authorized service persons.
Failure to so do can result in death or carbon monoxide
poisoning.
IMPORTANT: Air for combustion and ventilation must not
come from a corrosive atmosphere. Any failure due to
corrosive elements in the atmosphere is excluded from
warranty coverage.
The following types of installation (not iimited to the
following) will require outdoor air for combustion due to
chemical exposure and may reduce but not eliminate the
presence of corrosive chemicals in the air:
•
beauty shops
• photo processing labs
• buildings with indoor pools
• water heaters installed in laundry, hobby, or craft
rooms
• water heaters installed near chemical storage areas
Combustion air must be free of acid-forming chemicals such
as sulfur, fluorine, and chlorine. These elements are found
in aerosol sprays, detergents, bleaches, cleaning solvents,
air fresheners, paint, and varnish removers, refrigerants,
and many other commercial and household products. When
burned, vapors from these products form highly corrosive acid
compounds. These products should not be stored or used
near the water heater or air inlet.
Combustion and ventilation air requirements are determined
by the location of the water heater. The water heater may
be located in either an open (unconfined) area or in a
confined area or small enclosure such as a closet or small
room. Confined spaces are areas with less than 50 cubic
feet for each 1,000 BTUH of the total input for all gas-using
appliances.
Unconfined Space
A water heater in an unconfined space uses indoor air for
combustion and requires at ieast 50 cubic feet for each
1,000 BTUH of the total input for all gas appliances. The
table below shows a few examples of the minimum square
footage (area) required for various BTUH inputs.
TABLE 3
BTUH Input
Minimum
Square
Feet with
8' Ceiling
Typical Room
with 8’ Ceiling
30,000 9 x 2 1
45,000 14 x20
60,000 1 5 x 2 5
75,000 15x 31
90,000 2 0 x 2 8
105,000 057 2 0 x 3 3
120,000 25x 30
135,000 2 8 x 3 0
IMPORTANT:
• The area must be open and be able to provide the
proper air requirements to the water heater. Areas that
are being used for storage or contain large objects
may not be suitable for water heater installation.
• Water heaters installed in open spaces in buildings
with unusually tight construction may still require out­
door air to function properly. In this situation, outside
air openings should be sized the same as for a con­
fined space.
• Modern home construction usually requires supplying
outside air into the water heater area.
Confined Space
For the correct and proper operation of this water heater,
ample air must be supplied for the combustion, ventilation,
and dilution of flue gases. Small enclosures and confined
areas must have two permanent openings so that sufficient
fresh air can be drawn from outside of the enclosure. One
opening shall be within 12 inches of the top and one within
12 inches of the bottom of the enclosure as shown in
Figure 4.
The size of each opening (free area) is determined by the
total BTUH input of all gas utilization equipment (i.e., water
heaters, furnaces, clothes dryers, etc.) and the method by
which the air is provided. The BTUH input can be found
on the water heater rating plate. Additional air can be
provided by two methods:
1. All air from inside the building.
2. All air from outdoors.
11