A.O. Smith VB/VW- 750 User Manual

11

                        

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.

This boiler MUST NOT be installed on carpeted floors. This boiler

is approved for installation on combusti ble 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 er

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.

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.

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.

In buildings of conventional frame, brick or stone construction, 

unconfined spaces may provide adequate air for com bustion.
If the unconfined space is within a build ing of tight construction

(build ings  using  the  following  construction:  weath er  strip ping,

heavy insulation, caulk ing, vapor barrier, etc.), air for com bus tion,

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 fined spaces in tightly con structed 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.

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.

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