A.O. Smith 400A - Manual (Page 7)

7
CLEARANCES
These heaters are approved for installation on combustible flooring
in an alcove when the minimum clearances from any combustion
construction are followed as indicated in Figure 4.
In all installations the minimum combustible clearances from any
vent piping shall be 0". Vent piping passing through a combustible
wall or ceiling must be a continuous run (no joints).
A service clearance of 24" (61 cm) should be maintained from
serviceable parts such as relief valves, thermostats, cleanout
openings, drain valves and venting connections.
Always disconnect electrical power before servicing the unit.
*ILLUSTRATION OF MINIMUM COMBUSTIBLE CLEARANCES
IN AN ALCOVE.
FIGURE 4.
HARD WATER
Where hard water conditions exist, water softening or the threshold
type of water treatment is recommended. This will protect the
dishwashers, coffee urns, water heaters, water piping and other
equipment.
See MAINTENANCE section for details of tank cleanout procedure.
AIR REQUIREMENTS
KEEP APPLIANCE AREA CLEAR AND FREE OF COMBUSTIBLE
MATERIALS, GASOLINE AND OTHER FLAMMABLE VAPORS
AND LIQUIDS.
DO NOT OBSTRUCT THE FLOW OF COMBUSTION AND
VENTILATING AIR.
WARNING
FOR SAFE OPERATION PROVIDE ADEQUATE AIR FOR
COMBUSTION AND VENTILATION. AN INSUFFICIENT SUPPLY
OF AIR WILL 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
CARBONING OR SOOTING OF THE COMBUSTION CHAMBER,
BURNERS AND FLUE TUBES AND CREATES A RISK OF
ASPHYXIATION.
MECHANICAL EXHAUSTING OF ROOM AIR
Where an exhaust fan is installed in the same room with a heater,
sufficient openings for air must be provided in the walls. UNDERSIZED
OPENINGS WILL CAUSE AIR TO BE DRAWN INTO THE ROOM
THROUGH THE HEATER’S VENTING SYSTEM, CAUSING POOR
COMBUSTION. SOOTING MAY RESULT IN SERIOUS DAMAGE
TO THE HEATER AND RISK OF FIRE OR EXPLOSION. IT CAN
ALSO CREATE A RISK OF ASPHYXIATION.
UNCONFINED SPACE
In buildings of conventional frame, brick or stone construction,
unconfined spaces may provide adequate air for combustion and
ventilation.
If the unconfined space is within a building of tight construction
(buildings using the following construction: weather stripping,
heavy insulation, caulking, vapor barrier, etc.), air for combustion
and ventilation must be obtained from outdoors. The installation
instructions for confined spaces in tightly constructed buildings must
be followed to ensure adequate air supply.
CONFINED SPACE
When drawing combustion air from inside a conventionally
constructed building to a confined space, such a space shall be
provided with two permanent openings, ONE IN OR WITHIN
12 INCHES (31 cm) OF THE ENCLOSURE TOP AND ONE IN OR
WITHIN 12 INCHES (31 cm) OF THE ENCLOSURE BOTTOM. Each
opening shall have a free area of at least one square inch per 1000
Btuh (2,203mm /kW) appliances in the enclosure, but not less than
100 square inches (645 cm²).
If the confined space is within a building of tight construction, air
for combustion and ventilation must be obtained from outdoors.
When directly communicating with the outdoors through vertical
ducts, two permanent openings, located in the above manner,
shall be provided. Each opening shall have a free area of not
less than one square inch per 4000 Btuh (551mm /kW) of the
total input of all appliances in the enclosure. If horizontal ducts
are used, each opening shall have a free area of not less than one
square inch per 2000 Btuh (1,102mm /kW) of the total input of all
appliances in the enclosure.
CHEMICAL VAPOR CORROSION
WARNING
CORROSION OF THE FLUE WAYS AND VENT SYSTEM MAY
OCCUR IF AIR FOR COMBUSTION CONTAINS CERTAIN
CHEMICAL VAPORS. SUCH CORROSION MAY RESULT IN
FAILURE AND RISK OF ASPHYXIATION.
Spray can propellants, cleaning solvents, refrigerator and air
conditioning refrigerants, swimming pool chemicals, calcium
and sodium chloride, waxes, and process chemicals are typical
compounds which are potentially corrosive.
PRODUCTS OF THIS SORT SHOULD NOT BE STORED NEAR
THE HEATER. ALSO, AIR WHICH IS BROUGHT IN CONTACT
WITH THE HEATER SHOULD NOT CONTAIN ANY OF THESE
CHEMICALS. IF NECESSARY, UNCONTAMINATED AIR SHOULD
BE OBTAINED FROM REMOTE OR OUTSIDE SOURCES.