Olsen OSW, Installation Instruction

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FIGURE 8
FIGURE 9
27516101 PAGE 7 REV: 1.1, February 2004
B. One permanent opening, commencing within 12 inches of the top of the enclosure,
shall be permitted where the equipment has clearances of at least 1 inch from the sides, 1
inch from the back, and 6 inches from the front of the boiler. 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. The
openings must have a minimum free area of 1 square inch per 3000 Btu per hour of the total
input rating of all equipment located in the enclosure. The free area must be no less than the
sum of the areas of all vent connectors in the confined space.
6. In calculating free area using louvers, grilles or screens for the above, consideration
shall be given to their blocking effect. Screens used shall not be smaller than 1/4 inch mesh.
If the free area through a design of louver or grill is known, it should be used in calculating
the size opening required to provide the free area specified. If the design and free area is
not known, it may be assumed that wood louvers will have 20-25% free area and metal
louvers and grilles will have 60-75% free area. Louvers and grilles should be fixed in the open
position or interlocked with the boiler so they are opened automatically during the boiler
operation.