SBD TANK TYPE HEATERS
SERVICE HANDBOOK
MAKE-UP AIR
DIRECT COMMUNICATION
1 Square Inch Per 4,000 BTUH
A fresh supply of
-one within 12 inches of the top of the enclosure and one within twelve inches of the bottom of the enclosure. Each opening shall have a free area of not less than 1 square inch per 4000 BTUH of the total input of all appliances within the enclosure.
The lower opening is primarily providing combustion air. The upper opening is providing vent dilution air and acts as a relief opening for flue gases should the vent become obstructed or a downdraft condition occur. Additionally, when the heater is installed in a confined space and communicating with the outdoor air, one permanent opening, commencing within 12 in. (30 cm) of the top of the enclosure, shall be permitted where the equipment has clearances of at least 1 in. (2.5 cm) from the sides and back and 6 in. (16 cm) from the front of the appliance. The opening shall directly communicate with the outdoors and 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. in. per 3000 BTU per hr (7 cm2 per kW) of the total input of all equipment located in the enclosure, and
b.Not less than the sum of the areas of all vent connectors in the confined space.
Technical Training Department | 6 |
Ashland City, TN ©2003 |
