Furnace Vent Pipe: Venting High Efficiency Appliances & AL29-4C Pipe

Which Pipe Should I Use When Venting My Furnace, Boiler, or Corn Appliance?

High efficiency appliances such as furnaces and boilers are a great way to cut down on your heating bills. The more efficient an appliance is the less fuel that is being used. Every appliance is given an efficiency rating. The efficiency rating is referred to as the amount of fuel that is being directly used to heat the home. High efficiency is obtained when heat from the flue is extracted before it is vented into the atmosphere. To classify an appliance as highly efficient, the efficiency rating is going to be 86% or higher.

When the sulfur and chloride concentrate found in natural gas condenses, it produces a very acidic solution. After repeated heating and condensing cycles, highly corrosive material can build upon the walls of the flue. Brick and mortar chimneys have mortar joints that will be eaten away pretty quickly by this material. Pitting will occur in normal 304 and 316 stainless steel chimney liners. AL29-4C stainless steel venting pipe is the premier liner to choose when venting a high efficiency appliance.

AL29-4C flexible venting pipes are installed the same way as the 316Ti stainless steel flexible liners. All the connections are made the same way; just the type of metal is different. No special gaskets are used in conjunctions with AL29-4C liners. The AL29-4C flexible venting pipes are only to be used with category 1 residential appliances.

What is AL29-4C?

AL29-4C is a combination of many materials where the "AL" stands for Allegheny Ludlum. AL29-4C alloy was developed to prevent corrosion and breakdown in flues venting high efficiency gas, oil, and corn burning appliances. AL29-4C is made up of carbon, manganese, phosphorus, sulfur, silicon, chromium, nickel, molybdenum, nitrogen, titanium, columbium, and iron. This blend of stainless steel will ensure a strong defense against high corrosive acids.

When TO and when NOT TO use AL29-4C Flue Liners

It is important to only use AL29-4C flue liners when venting an oil, gas, or corn burning appliance. These highly efficient appliances extract the heat from the flue before it enters the atmosphere. In doing this, the flue temperature is much lower compared to that of solid fuel burners. Solid fuel appliances such as wood, wood pellets and coal produce much higher flue temperatures. The AL29-4C liner cannot stand up to the extreme temperatures that wood, wood pellets and coal produce. AL29-4C stainless steel pipes should not exceed a flue temperature of over 600 degrees Fahrenheit. Wood, wood pellets and coal appliances should only be vented with a 316Ti stainless steel chimney liner.

If you have any questions about chimney liners, please feel free to call us at Rockford Chimney Supply — we're happy to help!