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AIR FOR COMBUSTION AND VENTILATION

Determining Fresh-Air Flow For Heater Location

AIR FOR COMBUSTION AND VENTILATION

Continued

DETERMINING FRESH-AIR FLOW FOR HEATER LOCATION

Determining if You Have a Confined or Unconfined Space

Use this work sheet to determine if you have a confined or unconfined space.

Space: Includes the room in which you will install heater plus any adjoining rooms with doorless passageways or ventilation grills between the rooms.

1.Determine the volume of the space (length x width x height). Length x Width x Height = ___________ cu. ft. (volume of space)

Example: Space size 20 ft. (length) x 16 ft. (width) x 8 ft. (ceiling height) = 2560 cu. ft. (volume of space)

If additional ventilation to adjoining room is supplied with grills or open- ings, add the volume of these rooms to the total volume of the space.

2.Multiply the space volume by 20 to determine the maximum Btu/Hr the space can support.

__________ (volume of space) x 20 = (Maximum Btu/Hr the space

can support)

Example: 2560 cu. ft. (volume of space) x 20 = 51,200 (maximum Btu/Hr the space can support)

3.Add the Btu/Hr of all fuel burning appliances in the space.

Vent-free heater

 

_____________ Btu/Hr

Gas water heater*

 

_____________ Btu/Hr

Gas furnace

 

_____________ Btu/Hr

Vented gas heater

 

_____________ Btu/Hr

Gas fireplace logs

 

_____________ Btu/Hr

Other gas appliances* +

_____________ Btu/Hr

Total

=

_____________ Btu/Hr

*Do not include direct-vent gas appliances. Direct-vent draws com- bustion air from the outdoors and vents to the outdoors.

Example:

 

 

 

Gas water heater

 

40,000

Btu/Hr

Vent-free heater

 

39,000

 

+ _____________ Btu/Hr

Total

=

79,000

Btu/Hr

4.Compare the maximum Btu/Hr the space can support with the actual amount of Btu/Hr used.

__________________ Btu/Hr (maximum the space can support)

__________________ Btu/Hr (actual amount of Btu/Hr used)

Example: 51,200 Btu/Hr (maximum the space can support) 79,000 Btu/Hr (actual amount of Btu/Hr used)

The space in the above example is a confined space because the actual Btu/ Hr used is more than the maximum Btu/Hr the space can support. You must provide additional fresh air. Your options are as follows:

A.Rework worksheet, adding the space of an adjoining room. If the extra space provides an unconfined space, remove door to adjoining room or add ventilation grills between rooms. See Ventilation Air From Inside Building, page 7.

B.Vent room directly to the outdoors. See Ventilation Air From Out- doors, page 7.

C.Install a lower Btu/Hr heater, if lower Btu/Hr size makes room unconfined.

If the actual Btu/Hr used is less than the maximum Btu/Hr the space can support, the space is an unconfined space. You will need no additional fresh air ventilation.

WARNING: If the area in which the heater may be operated is smaller than that defined as an uncon- fined space or if the building is of unusually tight construction, provide adequate combustion and ven- tilation air by one of the methods described in the National Fuel Gas Code, ANSI Z223.1/NFPA 54 Sec- tion 5.3 or applicable local codes.

For..com

110021-01A

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Desa VRL24NT Determining FRESH-AIR Flow for Heater Location, Determining if You Have a Confined or Unconfined Space
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