AIR for Combustion and Ventilation

AIR FOR COMBUSTION AND VENTILATION

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DETERMINING AIR FLOW FOR HEATER LOCATION

Determining if You Have a Confined or Unconfined Space

Use this worksheet 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 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 openings, add the volume of these rooms to the total volume of the space.

2.Divide the space volume by 50 cubic feet to determine the maximum BTU/Hr the space can support.

____________ (volume of space) ÷ 50 cu. ft. = (Maximum BTU/Hr

the space can support)
Example: 2560 cu. ft. (volume of space) ÷ 50 cu. ft. =	51.2 or 51,200 (maximum
BTU/Hr the space can support)

3. Add the BTU/Hr of all fuel burning appliances in the space.

Vent-free heater		___________________ 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
Example: Gas water heater		30,000		BTU/Hr
Vent-free heater	+		28,000	BTU/Hr
Total	=	58,000		BTU/Hr

*Do not include direct-vent gas appliances. Direct-vent draws combustion air from the outdoors and vents to the outdoors.

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)
58,000	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 10.

B.Vent room directly to the outdoors. See Ventilation Air From Outdoors, page 11.

C.Install a lower BTU/Hr heater, 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 unconfined space. You will need no additional fresh air ventilation.

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