Desa VTD-24N-PDG, VTD-24N-BTB Determining FRESH-AIR Flow for Appliance Location, Ventilation AIR

AIR FOR COMBUSTION AND VENTILATION Providing Adequate Ventilation (Cont.)

Determining Fresh-Air Flow for Appliance Location Ventilation Air

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AIR FOR COMBUSTION AND VENTILATION

Continued

Confined and Unconfined Space

The National Fuel Gas Code, ANSI Z223.1/NFPA 54 defines a confined space as a space whose volume is less than 50 cubic feet per 1,000 Btu per hour (4.8 m3 per kw) of the aggregate input rating of all appliances installed in that space and an unconfined space as a space whose volume is not less than 50 cubic feet per 1,000 Btu per hour (4.8 m3 per kw) of the aggregate input rating of all appli- ances installed in that 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.

*Adjoining rooms are communicating only if there are doorless passageways or ventilation grills between them.

DETERMINING FRESH-AIR FLOW FOR APPLIANCE 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 appliance 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 appliance		_____________ Btu/Hr
Gas water appliance*		_____________ Btu/Hr
Gas furnace		_____________ Btu/Hr
Vented gas appliance		_____________ 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:		40,000
Gas water appliance
		_____________ Btu/Hr
Vent-free appliance	+	33,000
		_____________ Btu/Hr
Total	=	73,000
		_____________ 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) 73,000 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 6.

B.Vent room directly to the outdoors. See Ventilation Air From Outdoors, page 6.

C.Install a lower Btu/Hr appliance, if lower Btu/Hr size makes room uncon- fined.

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

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

VENTILATION AIR

Ventilation Air From Inside Building

This fresh air would come from an adjoining unconfined space. When ventilating to an adjoining unconfined space, you must provide two permanent openings: one within 12" of the ceiling and one within 12" of the floor on the wall connecting the two spaces (see options 1 and 2, Figure 2). You can also remove door into adjoining room (see option 3, Figure 2). Follow the National Fuel Gas Code, ANSI Z223.1/NFPA 54, Section 5.3, Air for Combustion and Ventilation for required size of ventilation grills or ducts.

Ventilation Air From Outdoors

Provide extra fresh air by using ventilation grills or ducts. You must provide two permanent openings: one within 12" of the ceil- ing and one within 12" of the floor. Connect these items directly to

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