Unconfined Space; Confined Space; Venting Installation; Venting - AO Smith BTR120 Manuel D'instructions

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 cubic meters 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.

VENTING

THE INSTRUCTIONS IN THIS SECTION ON VENTING MUST
BE FOLLOWED TO AVOID CHOKED COMBUSTION OR
RECIRCULATION OF FLUE GASES. SUCH CONDITIONS CAUSE
SOOTING OR RISKS OF FIRE AND ASPHYXIATION.
Heater must be protected from freezing downdrafts.
Remove all soot or other obstructions from the chimney that will retard
a free draft.
Type B venting is recommended with these heaters. For typical venting
application see TECHNICAL DATA VENTING on pages 19 and 20.
This water heater must be vented in compliance with all local codes,
the current revision of the National Fuel Gas Code (ANSI-Z223.1) and
with the Category I Venting Tables.
If any part of the vent system are exposed to ambient temperatures
below 40°F it must be insulated to prevent condensation.
• Do not connect the heater to a common vent or chimney with solid
fuel burning equipment. This practice is prohibited by many local
building codes as is the practice of venting gas fired equipment to
the duct work of ventilation systems.
• Where a separate vent connection is not available and the vent pipe
from the heater must be connected to a common vent with an oil
burning furnace, the vent pipe should enter the smaller common
vent or chimney at a point above the large vent pipe.

VENT REDUCER

Model BTR 120 is shipped with a 6" to 5" flue outlet adapter. Models
BTR 250, 251 and 275 are shipped with a 8" to 6" flue outlet adapter.
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.

VENTING INSTALLATION

Each adapter fits on top of the installed flue damper. Use only vent
reducers supplied with the unit. The venting must comply with the
current editions of the NATIONAL FUEL GAS CODE, ANSI Z223.1/
NFPA 54 or NATURAL GAS AND PROPANE INSTALLATION CODE
CAN/CSA-B149.1
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FIGURE 11.
FIGURE 12.