Combustion Air Supply & Ventilation; Air Requirements; Unconfined Space; Unusually Tight Construction - Kenmore 153.331350 Use & Care Manual

Air Requirements
For safe operation an adequate supply of fresh,
uncontaminated air for combustion, dilution and
ventilation must be provided.
NOTE: Contaminated or dusty air may cause build-
up on the blower wheel resulting in nuisance shut
downs.
An insufficient supply of air can cause recirculation
of combustion products resulting in contamination
that may be hazardous to life. Such a condition
often will result in a yellow, luminous burner flame,
causing sooting of the combustion chamber,
burners and flue tubes and creates a risk of
asphyxiation.
Do not install the water heater in a confined space
unless an adequate supply of air for combustion,
dilution and ventilation is brought into that space
using the methods described in the "Confined
Space" section that follows.
Never obstruct the flow of combustion, dilution and
ventilation air. If you have any doubts or questions
at all, call your gas supplier. Failure to provide
the proper amounts of air can result in a fire or
explosion and cause property damage, serious
bodily injury or death. The combustion and dilution
air inlets are shown in Figure 2.
Unusually Tight Construction
In unconfined spaces in buildings, infiltration
may be adequate to provide air for combustion,
ventilation and dilution of flue gases. However,
in buildings of unusually tight construction (e.g.,
weather stripping, heavily insulated, caulked, vapor
barrier, etc.) additional air must be provided using
the methods described in the "Confined Space"
section that follows.
Confined Space
A Confined Space is one whose volume is less than
50 cubic feet per 1,000 Btu/hr (4.8m3/kW) of the
total input rating of all appliances installed in the
space.
Openings must be installed to provide fresh air for
combustion, ventilation and dilution in confined
spaces. The required size for the openings is
dependent on the method used to provide fresh
air to the confined space and the total Btu/hr input
rating of all appliances installed in the space.
Direct Vent Appliances
Other appliances installed in a Direct Vent
configuration that derive all air for combustion from
the outdoor atmosphere through sealed intake air
piping are not factored in the total appliance input
Btu/hr calculations used to determine the size of
openings providing fresh air into confined spaces.
IMPORTANT: Power Vented water heaters require
air for combustion and dilution air for the blower.
Adequate ventilation air is required to minimize heat
buildup around the heater.
Unconfined Space
An Unconfined Space is one whose volume is not
less than 50 cubic feet per 1,000 Btu/hr (4.8m3/kW)
of the total input rating of all appliances installed in
the space. Rooms communicating directly with the
space in which the appliances are installed, through
openings not furnished with doors, are considered
a part of the unconfined space.
Exhaust Fans
Where exhaust fans are installed, additional air
should be provided to replace the exhausted air.
When an exhaust fan is installed in the same space
with a water heater, sufficient openings to provide
fresh air must be provided that accommodate the
requirements for all appliances in the room and the
exhaust fan. Undersized openings will cause air to
be drawn into the room through the water heater's
vent system causing poor combustion. Sooting,
serious damage to the water heater and the risk of
fire or explosion may result. It can also create a risk
of asphyxiation.
Makeup air requirements for the operation of
exhaust fans, kitchen ventilation systems, clothes
dryers and fireplaces should also be considered
in determining the adequacy of a space to provide
combustion, ventilation and dilution air.
Fresh Air Openings For Confined Spaces
The following instructions should be used to
calculate the size, number and placement of
openings providing fresh air for combustion,
ventilation and dilution in confined spaces. The
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