Exposure to the following substances in the combustion air supply may also require outdoor air for combustion:
??Aerosols
??Permanent wave solutions
??Chlorinated waxes, bleaches and cleaners
??Cat litter
??
??Cleaning solvents
??Paint removers and varnishes
??Adhesives
??
??Most refrigerants
WARNING: Combustion air that contains chlorine, fluorine, bromine or iodine could cause corrosion in heat exchanger and may result in nausea or death by asphyxiation.
UNCONFINED SPACE INSTALLATION (non-direct vent)
The National Fuel Gas Code, ANSI Z223.1/NFPA 54 and CAN/CGA B149 Installation Codes do not require that you make special provisions for combustion and ventilation air when furnace is in an "unconfined space" and building is not of "unusually tight construction."
??"Unconfined spaces" have a volume of at least 50 cubic feet per 1000 Btu per hour combined input rating of all appliances installed in the space. For example: a 100,000 Btu/hr furnace and a 40,000 Btu/hr water heater would require a volume of at least 140,000 X 50 ÷ 1,000 or 7,000 cubic feet.
??"Unusually tight construction" means windows and doors are either tight fitting or are sealed construction and that walls are covered with a continuous, sealed vapor barrier and drywall or similar materials having sealed joints.
If you meet the volume requirements for unconfined space, the building is not of unusually tight construction and there are no airborne contaminants, as listed above, you may install this furnace without making special provisions for combustion and ventilation air. Otherwise, follow the instructions for "confined space installation" below or direct vent the furnace using two pipes.
CONFINED SPACE INSTALLATION (non-direct vent)
A
WARNING: You must provide permanent air openings to a confined furnace installation space from another area as described below. Failure to do so could cause inadequate combustion and ventilation air and may result in nausea or death by asphyxiation.
ALL COMBUSTION AND VENTILATION AIR FROM INSIDE THE BUILDING
The confined furnace space must be provided with two permanent openings to an additional room of sufficient volume so that the combined volumes of the spaces meet the criteria above for an unconfined space not of unusually tight construction. The total input of all gas appliances within the combined space must be considered in making this determination.
Each opening must have minimum free area of one square inch per 1,000 Btu per hour of the total combined input rating of all gas appliances within the confined furnace space, but not less than 100 square inches. One opening must be within 12 inches of the top and one opening within 12 inches of the bottom of the furnace space. The shortest side of each air opening must be at least 3 inches long. See Figure 9.
For example:
??A 90,000 Btu/hr furnace and a 40,000 Btu/hr water heater would require free area openings of 130,000 ÷ 1,000 or 130 square inches.
??A 54,000 Btu/hr furnace and a 40,000 Btu/hr water heater would require the minimum free area openings of 100 square inches.
Figure 9. Confined Space, All Air From Inside The Building.
ALL COMBUSTION AND VENTILATION AIR FROM OUTDOORS
The furnace space must be provided with two permanent air openings communicating directly, or by ducts, with the outdoors or spaces that freely access the outdoors. Well- ventilated attics or crawl spaces usually satisfy this requirement. These openings will give furnace free access to fresh air for combustion and ventilation.
Page 12 | Installer’s Information Manual |
