High Efficiency Gas Furnace Exhaust

Traditional gas fired forced air furnaces produce hot combustion exhaust gasses and therefore need metal vent pipes or chimneys.

High efficiency gas furnace exhaust.

In a great majority of cases plastic piping is used to vent high efficiency equipment. When exhaust gases discharged from a high efficiency furnace exhaust vent meets the cold air the air condenses faster than conventional furnaces because it is cooler. A high efficiency furnace uses a different type of venting system because it extracts the heat that remains in those combustion gases before venting the resultant mixture of water and carbon dioxide. In standard furnaces all these combustion gases including carbon monoxide are usually vented through chimneys or flues.

Condensing gas furnaces achieve their high levels of efficiency by adding another step to the fuel burning and venting process. The condensing furnace flue exhaust is relatively cool and can be vented with a plastic vent pipe without use of a metal chimney vent. This condensing process along with the one that occurs within the high efficiency furnace itself creates moisture that can collect and freeze around and inside exhaust pipes since it can t travel far enough away from the home before condensing. This residual liquid is highly acidic.

It is classified as type bh venting. High efficiency or condensing furnaces exhaust the combustion gases and bring in fresh air through pvc pipes to the outside usually routed through the sidewall of the house. If not installed correctly or checked regularly problems in these pipes can affect the operation of the furnace itself. Venting for high efficiency gas furnaces materials due to the condensing nature of a high efficiency furnace its venting must be made of a material that is resistant to corrosion.

A conventional furnace vents these combustion gases through a vertical exhaust system that is attached to the furnace. In contrast modern high efficiency condensing furnaces exhaust much cooler gasses and need only plastic pipe materials such as pvc cpvc or abs for their exhaust vents. It uses a venting system to extract that heat before venting. Some products like furnaces may also be affected by installation orientation horizontal upflow or downflow or even by the nozzle used in installation as is the case with boilers and oil furnaces.

Overall efficiency p efficiency within a model group will tend to vary by the size capacity of the unit. Some high efficiency furnaces also include a plastic pipe for intake area and all types use a third plastic pipe to drain away the corrosive condensation resulting from the combustion process. A high efficiency condensing furnace can achieve efficiency ratings of 90 or above. What is vented is a residual corrosive condensate of water and carbon dioxide.