Continued | Desa CGD3018PT/NT, CRL2718P/N, CRL3124P/N, CGD3924PT/NT

DETERMINING FRESH-AIR FLOW FOR HEATER LOCATION

AIR FOR COMBUSTION

AND VENTILATION

Continued

Unusually Tight Construction

The air that leaks around doors and windows may provide enough fresh air for combustion and ven- tilation. However, in buildings of unusually tight construction, you must provide additional fresh air.

Unusually tight construction is defined as construction where:

a.walls and ceilings exposed to the out- side atmosphere have a continuous water vapor retarder with a rating of one perm (6x10-11kg 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 ar- eas such as joints around window and door frames, between sole plates and floors, between wall-ceiling joints, be- tween 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 additional fresh air. See Ventilation Air From Outdoors, page 7.

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

Confined and Unconfined Space

National Fuel Gas Code, ANSI Z223.1/NFPA 54 defines a confined space as a space whose vol- ume 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 un- confined 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 ap- pliances installed in that space. Rooms communi- cating directly with the space in which the appli- ances are installed*, through openings not fur- nished with doors, are considered a part of the un- confined space.

*Adjoining rooms are communicating only if there are doorless passageways or ventilation grills be- tween them.

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 fireplace plus any adjoining rooms with doorless pas- sageways 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) = 2,560 cu. ft. (vol- ume of space)

If additional ventilation to adjoining room is sup- plied 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 = (Maxi-

mum Btu/Hr the space can support)

Example: 2,560 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 fireplace	_________ 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. Di- rect-vent draws combustion air from the outdoors and vents to the outdoors.

Example:		40,000
Gas water heater
	_____________ Btu/Hr
Vent-free fireplace	+	39,000
	_____________ Btu/Hr
Total	=	39,000
	_____________ 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)

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