Crown Boiler AWR Series Installation Instructions Manual page 13

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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.
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If motorized louvers are installed in the openings to the outdoors, they must be interlocked to prevent operation of
the fuel burning appliances in the boiler room unless the louvers are open.
A mechanical system may be used to bring all combustion air to the boiler which meets all of the following requirements:
1) The system must be manufactured specifically for this purpose.
2) Size the system to deliver combustion air at the rate prescribed by the system manufacturer's instructions, but no less
than 0.35 CFM for each 1000 BTU/hr of the combined input of all fuel burning appliances in the boiler room. If
exhaust fans are present within the building, additional capacity may be required to prevent the boiler room from being
depressurized.
3) The system must be interlocked to prevent operation of the fuel burning appliances in the boiler room if the system is not
operating.
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
Mechanical Combustion Air Supply
6" MAX
6" MAX
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6" MAX
6" MAX