Operating instructions

2. Wherecommunicatingwiththeoutdoorsthroughhorizontalducts(seeFigure 3D), each opening shall have a minimum free area
of 1 area ofsq. in. per 2000 Btu per hour of total rating of all equipment in the enclosure.
Figure 3D - Horizontal Ducts Communicating to the Outdoors
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
8 ½"x16" 256,000 192,000 64,000
Louver Allowance
The free areas of openings means the area after reduction for any
installed louvers or grilles. Be sure to consider this reduction when
sizing the air openings.
Method B:One permanent opening commencing within 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 to a crawl space or attic that freely com-
municate with the out doors, and shall have a minimum free area off
1. 1 sq. inch per 3000 Btu per hour of the total input of all equipment located in the enclosure (see chart below).
2. Not less than the sum of the areas of all vent connectors in the confined space.
3"x12" 108,000 81,000 27,000
8"x 8" 192,000 144,000 48,000
8"x12" 288,000 216,000 72,000
8 ½"x 16" 384,000 288,000 96,000
Louver Allowance
The free areas of openings means the area after reduction for any
installed louvers or grilles. Be sure to consider this reduction when
sizing the air openings.