Air Requirements; Unconfined Space; Confined Space - A.O. Smith BTH-120 Instruction Manual

air reQuirements

Breathing Hazard - Carbon Monoxide Gas
Install water heater in accordance with
the Instruction Manual and NFPA 54 or
CAN/CSA-B149.1.
To avoid injury, combustion and ventilation
air must be taken from outdoors.
Do not place chemical vapor emitting
products near water heater.
Breathing carbon monoxide can cause brain damage or
death. Always read and understand instruction manual.
For safe operation an adequate supply of fresh uncontaminated
air for combustion and ventilation must be provided.
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 and ventilation is brought
in to that space using the methods described in the Confined
Space section that follows.
Never obstruct the flow of ventilation air. If you have any doubts
or questions at all, call your gas supplier. Failure to provide the
proper amount of combustion air can result in a fire or explosion
and cause property damage, serious bodily injury or death.

unconfined space

An Unconfined Space is one whose volume Is NoT lEss THaN
50 cubic feet per 1,000 Btu/hr (4.8 cubic meters per 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.
makeup air requirements for the operation of exhaust fans,
kitchen ventilation systems, clothes dryers and fireplaces shall
also be considered in determining the adequacy of a space to
provide combustion, ventilation and dilution air.
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 (for
example, 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 (4.8 cm per 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
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.
exhaust fans
Where exhaust fans are installed, additional air shall 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.
louVers and grilles
The free areas of the fresh air openings in the instructions that
follow do not take in to account the presence of louvers, grilles or
screens in the openings.
The required size of openings for combustion, ventilation and
dilution air shall be based on the "net free area" of each opening.
Where the free area through a design of louver or grille or screen
is known, it shall be used in calculating the size of opening
required to provide the free area specified. Where the louver and
grille design 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.
18