a.One opening MUST commence within
b.Size openings and ducts per Fig. 7 and Table 2.
c.TWO HORIZONTAL DUCTS require 1 square inch of free area per 2,000 Btuh (1,100 mm2/kW) of combined input for all gas appliances in the space per Fig. 7 and Table 2.
d.TWO OPENINGS OR VERTICAL DUCTS require 1 square inch of free area per 4,000 Btuh (550 mm2/kW) for combined input of all gas appliances in the space per Fig. 7 and Table 2.
3.ONE OUTDOOR OPENING requires:
a.1 square inch of free area per 3,000 Btuh (734 mm2/kW) for combined input of all gas appliances in the space per Table 2 and
b.Not less than the sum of the areas of all vent connectors in the space.
The opening shall commence within 12” (300 mm) of the ceiling. Appliances in the space shall have clearances of at least 1” (25
mm)from the sides and back and 6” (150 mm) from the front. The opening shall directly communicate with the outdoors or shall communicate through a vertical or horizontal duct to the outdoors or spaces (crawl or attic) that freely communicate with the outdoors.
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| 1 SQ IN. |
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| DUCTS |
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| PER 4000 |
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| BTUH* |
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| TO |
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| OUTDOORS |
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(305mm) 12″ MAX |
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| D | 12″ | (305mm) |
1 SQ IN. |
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| VENT | MAX | |
PER 2000 | B |
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| THROUGH | F |
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BTUH* | CIRULATINGC | AIR DUCTS |
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| ROOF | 1 SQ IN. |
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| PER |
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| 4000 |
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| BTUH* |
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DUCTS |
| OF COMBUSTION AIR | OPENINGS SHALL BE |
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| OUTDOORS |
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TO |
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OUTDOORS |
| AT LEAST 3 IN. |
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| 1 SQ IN. |
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| PER |
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| 4000 |
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1 SQ IN. |
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| BTUH* |
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| E | G |
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PER 2000 | A |
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BTUH* | RONTLEARANCINCEF | mm)(76 | 12″ | (305mm) | |||
(305mm) 12″ MAX |
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| C | MAX | |
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| 12″ MAX |
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| (305mm) |
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CIRCULATING AIR DUCTS | DUCT | 1 SQ IN. |
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| TO | PER 4000 |
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| OUTDOORS | BTUH* |
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*Minimum dimensions of 3 in. (76 mm).
NOTE: Use any of the following combinations of openings: A&B, C&D, D&E, F&G
A03174
Fig. 7 - Air for Combustion, Ventilation, and Dilution from
Outdoors
Indoor Combustion Air - NFPA & AGA
Standard and Known-Air-Infiltration Rate Methods
Indoor air is permitted for combustion, ventilation, and dilution, if the Standard or
!WARNING
CARBON MONOXIDE POISONING HAZARD
Failure to follow this warning could result in death and/or personal injury.
Many homes require air to be supplied from outdoors for furnace combustion, ventilation, and dilution of flue gases. The furnace combustion air supply must be provided in accordance with this instruction manual.
The Standard Method:
1.The space has no less volume than 50 cubic feet per 1,000 Btuh of the maximum input ratings for all gas appliances installed in the space and
2.The air infiltration rate is not known to be less than 0.40 air changes per hour (ACH).
The Known Air Infiltration Rate Method shall be used, if the infiltration rate is known to be:
1.Less than 0.40 ACH and
2.Equal to or greater than 0.10 ACH
Infiltration rates greater than 0.60 ACH shall not be used. The minimum required volume of the space varies with the number of ACH and shall be determined per Table 3 or Equations 1 and 2. Determine the minimum required volume for each appliance in the space and add the volumes together to get the total minimum required volume for the space.
Table
1.For other than
Volume | = | 21ft3 | I other | |
ACH | 1000 Btu/hr | |||
Other |
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A04002
2.For
Volume | = | 15ft3 | I fan | |
ACH | 1000 Btu/hr | |||
Fan |
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A004003
If:
Iother = combined input of all other than
Ifan = combined input of all
The following requirements apply to the Standard Method and to the Known Air Infiltration Rate Method.
1.Adjoining rooms can be considered part of a space if:
a.There are no closable doors between rooms.
b.Combining spaces on same floor level. Each opening shall have free area of at least 1 in.2/1,000 Btuh (2,000 mm2/kW) of the total input rating of all gas appliances in the space, but not less than 100 in.2 (0.06 m2). One opening shall commence within 12” (300 mm) of the ceiling and the second opening shall commence within 12” (300 mm) of the floor. The minimum dimension of air openings shall be at least 3 in. (80 mm). (See Fig. 8.)
c.Combining space on different floor levels. The volumes of spaces on different floor levels shall be considered as communicating spaces if connected by one or more permanent openings in doors or floors having free area
58PHA
9