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TABLE 3
BTUH Input
Minimum
Square
Feet with
8’ Ceiling
Typical Room
with 8’ Ceiling
30,000 188 9 x 21
45,000 281 14 x 20
60,000 375 15 x 25
75,000 469 15 x 31
90,000 563 20 x 28
105,000 657 20 x 33
120,000 750 25 x 30
135,000 844 28 x 30
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 un-
usually tight construction may still require outdoor air to func-
tion properly. In this situation, outside air openings should be
sized the same as for a confined space.
• Modern home construction usually requires supplying out-
side 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 13.
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.
COMBUSTION AIR & VENTILATION
WARNING
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 personel, 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 limited 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 least 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.