Desa GS38 Determining FRESH-AIR Flow for Heater Location, Confined and Unconfined Space

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 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 doorless passageways or ventilation grills between 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 22 ft. (length) x 18 ft. (width) x 8 ft. (ceiling height) = 3168 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 = (Maxi- mum Btu/Hr the space can support)

Example: 3168 cu. ft. (volume of space) x 20 = 63,360 (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	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: 63,360 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 maxi- mum 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 adjoin- ing 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 8.

B.Vent room directly to the outdoors. See Ventila- tion Air From Outdoors, page 8.

C.Install a lower Btu/Hr fireplace, 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 un- confined space. You will need no additional fresh air ventilation.

WARNING: If the area in which the fireplace 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/NFPA54 Section 5.3 or applicable local codes.

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