Chemical Vapor Corrosion; Installtion Clearances; Leveling; Air Requirements - A.O. Smith VB-500, VB-750 Instruction Manual

CHEMICAL VAPOR CORROSION

Boiler corrosion and component failure can be caused by the
heating and breakdown of airborne chemical vapors. Spray can
propellants, cleaning sol vents, refrigerator and air conditioning
refrig erants, swimming pool chemicals, calcium and sodium
chloride (water softener salt), waxes, and process chemicals are
typical compounds which are potentially corrosive. These materials
are corrosive at very low con centration levels with little or no odor
to reveal their presence.
Products of this sort should not be stored near the boiler. Also, air
which is brought in contact with the boiler should not contain any
of these chemicals. If necessary, uncontaminated air should be
obtained from remote or outside sources. Failure to observe this
requirement will void the warranty.

INSTALLTION CLEARANCES

This boiler MUST NOT be installed on carpeted floors. This boiler
is approved for installation on combusti b le flooring in an alcove with
minimum clearances to combustibles of:
4" (102mm) Rear; 0" (0mm) Top and Sides; 6" (152mm) Vent. 2" (51mm)
clearance is allowable from combustible construction for hot water pipes.
Sufficient area should be provided at the front and rear of the unit for prop e r
servicing. Service clearances of 24" (610mm) in front, rear, top and sides
are recommended. In a utility room installa tion, the door opening shall be
wide enough to allow the boiler to enter or to permit the replacement of
another appli ance such as a boiler.

LEVELING

Each unit should be checked after in stal lation to be certain
that it is level.
If the unit is not level, obtain and insert shims under the feet at the
frame base to correct this condition.

AIR REQUIREMENTS

Breathing Hazard - Carbon Monoxide Gas
Install appliance 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.
FIGURE 8.

UNCONFINED SPACE

In buildings of conventional frame, brick or stone construction,
unconfined spaces may provide adequate air for com b ustion.
If the unconfined space is within a build i ng of tight construction
(build i ngs using the following construction: weath e r strip p ing,
heavy insulation, caulk i ng, vapor barrier, etc.), air for com b us t ion,
venti lation, and draft hood di lu tion must be obtained from outdoors
or spaces freely communicating with the outdoors. The installation
instructions for con fi ned spaces in tightly con s tructed buildings
must be followed to ensure adequate air supply.
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 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
appliance vent system causing poor combustion. Sooting, serious
damage to the appliance 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 should 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 should 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 should 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
should be fixed in the open position.

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
illustrations shown in this section of the manual are a reference
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