Desa VFRMV24NA, VFRMV18NA, VFRMV18PA Determining FRESH-AIR Flow for Appliance Location

AIR FOR COMBUSTION AND VENTILATION

Providing Adequate Ventilation (Cont.)

Determining Fresh-Air Flow for Appliance Location

5

AIR FOR COMBUSTION AND

VENTILATION

Continued

Unusually tight construction is defined as construction where:

A.Walls and ceilings exposed to the outside atmosphere have a con tinuous water vapor retarder with a rating of one perm (6 x 10-11kg per pa-sec-m2) or less with openings gasketed or sealed and

B.weather stripping has been added on openable windows and doors and

C.caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between wall-ceiling joints, between wall panels, at penetrations for plumbing, electrical, and gas lines, and at other openings.

If your home meets all of the three criteria above, you must provide ad ditional fresh air. See Ventilation Air From Outdoors, page 5.

If your home does not meet all of the three criteria above, proceed to Determining Fresh-Air Flow For Appliance Location, below.

Confined and Unconfined Space

The National Fuel Gas Code,ANSI Z223.1/NFPA54 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 appliances 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 odorless 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 odorless 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 openings, 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 combustion air from the outdoors and vents to the outdoors.

Example:

Gas water appliance		40,000	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 unconfined.

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 oper- ated 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.

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