Watts Aerco Modulex EXT Series Technical Application Manual page 10

Modulex EXT Vent and Combustion Air Application Guide
3. When combustion air is brought from outside the building and the boiler room is provided with
two permanent openings, one shall commence 12 inches from the top and the other shall
commence within 12 inches from the bottom of the room (see Figure 5). The openings shall
communicate directly, or by ducts, freely with the outdoors. One of the following methods must
be made to provide adequate air for ventilation and combustion.
12" (305 mm)
MAKEUP AIR
MAKEUP AIR
12" (305 mm)
Figure 5: Combustion-Air Makeup-Air Vent Locations
o When directly communicating with the outdoors, each opening shall have a minimum free area
of 1 square inch per 4,000 BTU per hour of total input rating of all equipment in the room.
o When communicating with the outdoors by means of vertical ducts, each opening shall have a
minimum free area of 1 square inch per 4,000 BTU per total input rating of all appliances in the
room.
o If horizontal ducts are used, each opening and duct shall have a minimum free area of 1
square inch per 2,000 BTU per hour of total input rating of all appliances in the room.
4. When calculating free area using louvers and grilles, the required size of the openings for
combustion, ventilation, and dilution air shall be based on the total free area of each opening.
5. If the free area through a designed louver or grille is known, it shall be used in calculating the size
of the opening required to provide the free area specified.
6. If the louver and grille design free areas are not known, the following will be assumed for wooden
louvers a 25 percent free area, and for metal louvers and grilles a 75 percent free area opening.
Page 10 of 28
09/25/2017
AERCO International, Inc. • 100 Oritani Dr. • Blauvelt, NY 10913
Phone: 800-526-0288
TAG-0054-0F
GF-136-V