Although many parts of a wood-burning furnace, such as the ductwork and blower assembly, are the same as for a gas furnace, the systems themselves are very different. For instance, wood fires burn constantly while gas furnaces have burners that turn on and off, depending on the temperature, so the combustion chambers have different requirements. In addition, each system needs a different type of chimney and draft. Only a few companies sell wood-burning furnaces that work with LP gas backup.
Charmaster’s combination wood/gas furnace is really two furnaces attached together at the bottom of the wood furnace jacket. This means that if you decide you don’t want the 80-percent efficient LP gas furnace the company provides, you can purchase its Wood/Controls furnace and hook it into the same ductwork as your own gas furnace. Charmaster combination furnaces come in two different sizes that heat either 2,000 or 5,000 square feet. Two separate chimneys are required: an 8-inch inside-diameter Class “A” chimney for the wood stove and a 4-inch inside-diameter Class “B” chimney for the gas stove. At the time of publication, these furnaces cost between $5,000 and $8,000 and came with a limited 20-year warranty.
Mahoning’s multi-fuel furnace is an outdoor furnace, which means smoke, fuel odors and carbon monoxide don’t enter your house. In addition to burning wood and LP gas, the furnace can burn a variety of other fuels and also can switch automatically between them when needed. The furnace connects to any forced air, hot water or in-floor radiant heating system and comes with a three-year warranty. Contact the dealer for information about prices.
Tarm’s multi-fuel furnace, the Excel 2200, consists of two furnaces in one chassis. One furnace burns wood, and the other burns LP gas. Although each furnace has its own combustion chamber and heat exchanger, both furnaces can be vented up the same flue. If the furnace runs out of wood, it will automatically switch over to the propane backup. The Excel 2200 has a maximum efficiency of 86 percent and comes with a limited 20-year warranty. At the time of publication, it cost between $12,500 and $14,000.
The Yukon-Eagle multi-fuel furnace will burn either coal or wood in one firebox and LP gas in the other. Dual thermostats allow the gas to come on when the fuel source burns out. When you put more wood or coal in, the gas will ignite it automatically. Yukon’s multi-fuel furnace is approved by Underwriter Laboratories and only requires one properly constructed chimney flue. The furnace also is approved as a gravity-flow wood/coal furnace, which means you can use the wood/coal furnace when the power goes out. The gas furnace is certified to be 80.1 percent efficient. The Yukon-Eagle comes with a 30-year limited warranty and costs between $5,000 and $7,000 at the time of publication.
- Inspectapedia: Combination Wood Burning or Coal-Burning Boilers, Furnaces, Fireplaces, Woodstoves
- Charmaster & Chalet: Forced Air Wood/Gas Furnaces – Indoor
- Charmaster: Chimney
- Mahoning Outdoor Furnaces: Why Buy a Mahoning Outdoor Furnace?
- Yukon-Eagle: Wood Trivia - Why Buy a Yukon-Eagle Multi-Fuel?
- Tarm Biomass: Multi-Fuel Boilers
- Tarm Biomass: HS Tarm Excel
- Yukon-Eagle: Thank You Letter