Gas Furnace Venting

Most old gas furnaces use the direct mechanism.

Gas furnace venting.

These tables are from the american gas association aga which co publishes them with the national fire protection association nfpa. In a mid efficiency furnace below 90 afue the combustion gases that are vented out are in the form of a gaseous vapor. This ensures that those in the building are not harmed by toxic gases and other byproducts of combustion. The design btuh british thermal units per hour capacity of the vent plus the furnace input and efficiency are factors affecting the temperature of the flue gases.

Install according to both the appliance manufacturer s and venting system manufacturer s instructions seal all seams under positive pressure no mixing with natural venting must have safety built in to shut off gas to burners if venting system is not working 24. This structure generally uses the furnace vent pipe through roofbecause the b venting pipe is designed in vertical manner. When the vent is withdrawing air from the house it expels the gas outside through the vent. The first is the direct vent which directly throws all the air into the atmosphere.

Modern furnaces use type b pipes which are more environmentally safe. The flue is also a safeguard against fire. The exhaust system typically uses metal venting often routed into a chimney stack to exhaust the combustion gases created in the furnace fire chamber. Gas furnace fumes are moist so if you notice sweat on your windows this is a sign that your furnace isn t venting correctly.

The vent pipe or flue is a vital component of the furnace that transmits emissions from the combustion process out of the building. When venting your gas furnace you need to know the different kinds of vents that can be installed. Also known as the type b this vent is operating on the natural air convection. Since hot vapor naturally rises the flue that s attached to the heat exchanger points upwards and extends all the way up and out of the roof.

Another clue could be rust on the grillwork on the front of your. Higher btuh furnaces produce higher flue gas temperatures. When your furnace comes on in the morning if it is venting into your house rather than outdoors moisture will condense on the cold glass.