Installation & Service Manual
1 Determine unit location (continued)
3. Combustion Air from an Interior Space
You can direct combustion air to this unit using air from an adjoining interior space. You must provide two openings from the boiler room to the adjoining room. Each of the two openings must have a net free area of one square inch per 1000 Btu input (22cm² per kW), but not less than 100 square inches (645cm²).
Figure 1-8_Combustion air from an interior space
All dimensions are based on net free area in square inches. Metal louvers or screens reduce the free area of a combustion air opening a minimum of approximately 25%. Check with louver manufacturers for exact net free area of louvers. Where two openings are provided, one must be within 12'' (30 cm) of the ceiling and one must be within 12'' (30 cm) of the floor of the equipment room. Each opening must have a minimum net free area as specified in TABLE 1B, page 12. Single openings shall be installed within 12'' (30 cm) of the ceiling.
Exhaust Fans
WARNING Any fan or equipment which exhausts air from the boiler room may deplete the
combustion air supply and/or cause a down draft in the venting system. Spillage of flue products from the venting system into an occupied living space can cause a very hazardous condition that must be corrected immediately. If a fan is used to supply combustion air to the boiler room, the installer must make sure that it does not cause drafts which could lead to nuisance operational problems with the boiler.
CAUTION
The combustion air supply must be completely free of any flammable vapors that may ignite or chemical fumes which may be corrosive to the appliance. Common corrosive chemical fumes which must be avoided are fluorocarbons and other halogenated compounds, most commonly present as refrigerants or solvents, such as Freon, trichlorethylene, perchlorethylene, chlorine, etc. These chemicals, when burned, form acids which quickly attack the heat exchanger finned tubes, headers, flue collectors, and the vent system. The result is improper combustion and a non- warrantable, premature unit failure.
15 
