Equipment located in buildings of unusually tight construction shall be provided with air for combustion, ventilation, and dilution of flue gases using the methods described in example 2B or shall be specially engineered. The authority having jurisdiction must approve specially engineered installations.
PROCEDURE 2ÐBOILER LOCATED IN CONFINED SPACE
EXAMPLE 2A: ALL AIR FROM INSIDE THE BUILDING
The confined space shall be provided with two permanent openings communicating directly with an additional room(s) of sufficient volume so that the combined volume of all spaces meets the criteria for an unconfined space. The total input of all gas utilization equipment installed in the combined space shall be considered in making this determination. Each opening shall have a minimum free area of one square inch per 1,000 Btu per hour of the total input rating of all gas utilization equipment in the confined space, but not less than 100 square inches. One opening shall be within 12 inches of the top and one within 12 inches of the bottom of the enclosure. The minimum dimension of air openings shall not be less than 3 inches.
EXAMPLE 2B: ALL AIR FROM OUTDOORS
The confined space shall communicate with the outdoors in accordance with examples 1 or 2. The minimum dimension of air openings shall not be less than 3 in. Where ducts are used, they shall be of the same
1.Two permanent openings, one commencing within 12 inches of the top, and one commencing within 12 inches of the bottom of the enclosure shall be provided. The openings shall communicate directly, or by the ducts, with the outdoors or spaces (crawl or attic) that freely communicate with the outdoors
a.Where directly communicating with the outdoors or where communicating to the outdoors through vertical ducts, each opening shall have a minimum free area of 1 sq. in. per 4000 Btu per hour of total input rating of all equipment in the enclosure. (See Table 3A.)
b.Where communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 sq. in. per 2000 Btu per hour of total input rating of all equipment in the enclosure. (See Table 3B.)
2.One permanent opening commencing with 12 inches of the top of the enclosure shall be permitted where the equipment has clearance of at least 1 inch from the sides and back and 6 inches from the front of the appliance. 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 and shall have a minimum free area of:
a.1 sq. inch per 3000 Btu per hour of the total input of all equipment located in the enclosure (see Table 3C), and
b.Not less than the sum of the areas of all vent connectors in the confined space.
Table 3AÐFresh Air Duct Capacities for Vertical Ducts (Btuh)*
| 100% FREE AREA | 75% FREE AREA | 25% FREE AREA |
Fresh Air | Metal | Wood | |
Duct Size (In.) | Screen | Louvers | Louvers |
3" X 12" | 144,000 | 108,000 | 36,000 |
|
|
|
|
8" X 8" | 256,000 | 192,000 | 64,000 |
|
|
|
|
8" X 12" | 384,000 | 288,000 | 96,000 |
512,000 | 384,000 | 128,000 | |
|
|
|
|
* 1 Square Inch per 4,000 Btuh
Table 3BÐFresh Air Duct Capacities for Horizontal Ducts (Btuh)*
| 100% FREE AREA | 75% FREE AREA | 25% FREE AREA |
Fresh Air | Metal | Wood | |
Duct Size (In.) | Screen | Louvers | Louvers |
|
|
|
|
3" X 12" | 72,000 | 54,000 | 18,000 |
|
|
|
|
8" X 8" | 128,000 | 96,000 | 32,000 |
8" X 12" | 192,000 | 144,000 | 48,000 |
|
|
|
|
256,000 | 192,000 | 64,000 | |
|
|
|
|
* 1 Square Inch per 2,000 Btuh
Table 3CÐFresh Air Duct Capacities for Vertical or Horizontal Ducts (Btuh)*
| 100% FREE AREA | 75% FREE AREA | 25% FREE AREA |
Fresh Air | Metal | Wood | |
Duct Size (In.) | Screen | Louvers | Louvers |
3" X 12" | 108,000 | 81,000 | 27,000 |
8" X 8" | 192,000 | 144,000 | 48,000 |
|
|
|
|
8" X 12" | 288,000 | 216,000 | 72,000 |
|
|
|
|
384,000 | 288,000 | 96,000 | |
|
|
|
|
* 1 Square Inch per 3,000 Btuh
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