PREINSTALLATION
i.Where communicating directly or through vertical ducts with the outdoors each opening shall have a minimum free area of 1 in2 per 4000 Btu/hr (22 cm2 per 4000 W) of total input rating for all equipment in the space. See Figure 1.4 for openings directly communicating with the outdoors or Figure 1.5 for openings connected by ducts to the outdoors.
Figure 1.4: Air Openings – All Air Directly from Outdoors
Figure 1.6: Air Openings – All Air from Outdoors through Horizontal Ducts
b.One Permanent Opening Method: Provide one permanent opening beginning within 12 inches (305 mm) of the top of the space. The opening shall communicate directly with the outdoors, communicate through a vertical or horizontal duct, or communicate with a space that freely communicates with the outdoors. The opening shall have a minimum free area of 1 in2 per 3000 Btu/hr of total rated input for all appliances in the space and not less than the sum of the cross-sectional areas of all vent connectors in the space. The gas-fired equipment shall have clearances of at least 1 inch (25 mm) from the sides and back and 6 inches (150 mm) from the front of the appliance. See Figure 1.7 for this arrangement.
Figure 1.5: Air Openings – All Air from Outdoors through Vertical Ducts
ii.Where communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 in2 per 2000
Btu/hr (22 cm2 per 2000 W) of total rated | Figure 1.7: Air Openings – All Air from Outdoors |
input for all appliances in the space. See | through One Opening |
Figure 1.6. |
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