American Water Heater VG6250T76NV Series 100 Benutzerhandbuch

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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.

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 should also be

considered  in  determining  the  adequacy  of  a  space  to  provide 

combustion, ventilation and dilution air.

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 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.

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.

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 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.

The free areas of fresh air openings in instructions that follow do not take 

in to account presence of louvers, grilles or screens in 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 for the openings that provide 

fresh air into confined spaces only. Do not refer to these illustrations

for the purpose of vent installation. See Installation of Vent System on 

pages 18-27 for complete venting installation instructions.

The  confined  space  should  be  provided  with  two  permanent 

openings, one commencing within 12 inches (300 mm) of the top

and one commencing within 12 inches (300 mm) of the bottom of

the enclosure. The openings should communicate directly with 

the outdoors. See Figure 6.
Each opening should have a minimum free area of 1 square inch 

per 4,000 Btu/hr (550 mm

2

per kW) of the aggregate input rating

of all appliances installed in the enclosure. Each opening should 

not be less than 100 square inches (645 cm

2

).

Alternatively a single permanent opening, commencing within 12 

inches (300 mm) of the top of the enclosure, should be provided. See