Furnace Makeup Air Requirements

By glenn mathewson issue 287 kitchens baths.

Furnace makeup air requirements.

Several options are also available for the outdoor and indirect indoor make up air unit. Our duct furnaces can be ordered with several different options so they fit your specific requirements. A furnace must be supplied a specific amount of fresh air per cubic foot of gas burned. Department of energy a defining feature of high efficiency furnaces is sealed combustion a process by which outdoor makeup air is piped directly into the burner.

To burn 1 cubic foot of gas approximately 1 000 btu for natural gas requires 10 cubic feet of air for perfect combustion figure 2. Makeup air for kitchen exhaust. The real requirement is that makeup air must be provided if it s needed. Ten cubic feet of air contains 2 cubic feet of oxygen and 8 cubic feet of nitrogen and other gases combined with water vapor.

Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system. The makeup air system consists of a make up air damper mounted on the return air duct of an hvac system and an intake air hood installed through an exterior wall to allow outdoor air into the home with the two being typically connected by installer supplied standard 6 galvanized sheet metal pipe. If an exhaust fan rated over 300 cfm is installed makeup air might be needed and a calculation will need to be done. According to the u s.

Of air per minute require makeup air so they don t depressurize the home and draw combustion gases from the appliance into the living space. Makeup air shall be mechanically or naturally provided makeup air systems shall be equipped with not less than one damper gravity dampers electrically operated damper that automatically opens when the exhaust system operates 26 2015 requirements adopted in pa. In homes with naturally drafted fuel fired appliances like a boiler inside the envelope kitchen range hoods that exhaust more than 400 cu. This means the heating system wouldn t be required to work any harder than is necessary nor would it waste energy.

Likewise if the outside air temperature is 10 f then the ventilation fan is bringing in 10 f air. The minnesota mechanical code is a combination of chapters 2 to 15 of the 2006 international mechanical code and minnesota s amendments. With a make up air unit that same 10 f air can be tempered to 50 f.