Crown Boiler AWR070 Installation Instructions Manual page 11

FIGURE 5.4: OUTDOOR COMBUSTION AIR METHOD: USING OPENINGS INTO BOILER ROOM
FIGURE 5.5: OUTDOOR COMBUSTION AIR METHOD: USING HORIZONTAL DUCTS INTO BOILER ROOM
1) Openings must be installed between the boiler room and the outdoors or a ventilated space, such as an attic or crawl
space, which communicates directly with the outdoors.
2) Two openings are required. The top edge of the upper opening must be within 12 inches of the ceiling. The bottom edge
of the lower opening must be within 12 inches of the floor.
3) Size openings and ducts as follows:
•
Vertical ducts or openings directly outdoors (Figure 5.2, Figure 5.3, and Figure 5.4) - Each opening must have a free
cross sectional area of 1 square inch per 4000 BTU/hr of the total input of all gas-fired appliances in the boiler room.
Minimum opening size is 3 inches.
•
Openings to outdoors via horizontal ducts (Figure 5.5) - Each opening must have a free cross sectional area of 1
square inch per 2000 BTU/hr of the total input of all gas fired appliances in the boiler room. Minimum opening size
is 3 inches.
•
The "free area" of an opening takes into account the blocking effect of mesh, grills, and louvers. Where screens are
used, they must be no finer than ¼" (4 x 4) mesh.
Using the Outdoor Combustion Air Method
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