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17
Carbon Monoxide Warning
Follow all the local and state codes or, in the absence of
local and state codes, the “National Fuel Gas Code”,
ANSI Z223.1 (NFPA 54)- current edition to properly
install vent system.
Failure to do so can result in death, explosion, or
carbon monoxide poisoning.
WARNING
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.
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
COMBUSTION AIR SUPPLY & VENTILATION
TABLE 3
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
unusually tight construction may still require outdoor air
to function properly. In this situation, outside air openings
should be sized the same as for a confined 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 12.
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.
12” MAXIMUM
PERMANENT
OPENINGS TO
T
HE OUTSIDE OR
ADDITIONAL
ROOMS WITHIN
THE BUILDING
CLOSET
OR
OTHER
CONFINED
SPACE
12” MAXIMUM
FIGURE 12.
All Air from Inside 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