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B. All Air from Outdoors: | The | confined | space | shall | be provided | with | two permanent | openings, | one | ||||||
commencing | within 12 | inches | of the | top | and | commencing | within |
| 12 | inches | of the | bottom of | the | ||
enclosure. | The | openings | shall | communicate | directly, | or | by ducts, | with the | outdoors | or spaces | (crawl or | ||||
attic) that | freely | communicate | with | the outdoors. |
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1.When directly communicating with the outdoors, each opening shall have a minimum free area of
one square inch per 4,000 Btu per hour of total input rating of all equipment in the enclosure.
2.When communicating with the outdoors through vertical ducts, each opening shall have a minimum
flee, area of one square inch per 4,000 Btu per hour of total input rating of all equipment in the enclosure.
3.When communicating with the outdoors through horizontal ducts, each opening shall have a
minimum free area of one square inch per 2,000 Btu per hour of total input rating of all equipment in the enclosure.
4.When ducts are used, they shall be of the same
which they connect. The minimum dimension of rectangular air ducts shall be not less than three inches.
FRESH
AIR
FRESH AIRDUCTCAPACITIESFORDUCTSSUPPLYINGFRESH_RTOBOILERINTIGHTLY
CONSTRUCTED HOUSES
Fresh | Air | ¼" Mesh Screen | Wood Louvers | Metal Louvers |
Duct | Size | (Btuh)* | (Btuh)* | (Btuh)* |
3J/2 '" x 12" | 144,000 | 36,000 | 108,000 | |
8" x 8" | 256,000 | 64,000 | 192,000 | |
8" x | 12" | 384,000 | 96,000 | 288,000 |
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8"x | 16" | 512,000 | 128,000 | 384,000 |
*Btuh = British Thermal Units per hour based on opening covered by ¼" mesh screen, wood louvers, or metal louvers.