Desa VSGF36NTA, VSGF36PRA, VSGF36PTA, VSGF36NRA 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 door- less 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 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:

Gas water heater		40,000	Btu/Hr
Vent-free fireplace	+	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: 63,360 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 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 9.

B.Vent room directly to the outdoors. See Ventila- tion Air From Outdoors, page 9.

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 maxi- mum 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 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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