Boilers are heating devices in residences and commercial buildings that generate heat using hot water and steam. For people living in large towns and cities, oil, electricity and natural gas are most commonly used as fuel for boilers and furnaces according to the U.S. Department of Energy (DOA). However, people living in rural areas may be more prone to use wood and propane as heating fuel. Combination wood and propane boilers can also be cheaper and more efficient options for occupants with only one chimney flue, or with older fossil fuel boilers that need to be replaced.
Combination wood and propane boilers allow users to switch between wood gasification and liquid propane heating mechanisms. While the wood portion derives heat value from combustible gases released from firewood, the fossil fuel portion generates heat from liquefied propane. These boilers contain separate combustion chambers and heat exchange tubes for each fuel type to ensure optimal energy efficiency. Combination wood and propane boilers are also appropriate for residents or businesses with basements that contain only one chimney flue for venting exhaust.
Purchasing a combination wood and propane gas boiler can be less costly than purchasing two separate boilers. They also require less space for equipment compared to multiple boilers. Moreover, gas boilers are estimated to be 85 percent efficient, while wood pellet fuel has an overall efficiency rating of 85 to 90, percent according to the DOA. In addition, recycled wood waste and propane are available throughout the United States. Using combination wood and propane boilers can be even more cost-effective if you can harvest and haul your own firewood.
Although harvested firewood is considered an efficient and clean energy source, it burns most efficiently when completely dry. Whereas a cord wood burned hot and dry has an equivalent fuel content of 150 gallons of oil, wet wood burned only has an equivalent fuel content of 60 gallons of oil, according to Energyworks. Likewise, select a wood and propane boiler that is properly sized for your building to ensure that it burns the cured wood at a high combustion efficiency. Also, compare the costs of wood and propane with how well combination boilers convert both fuels into useful heat. Heat distribution and delivery mechanisms should also be considered when choosing between a conventional boiler versus a combination or multi-fuel system.
Energyworks’ fall 2007 “Wood Boiler News” publication states that combination wood and propane boilers are a worthwhile investment if you need to replace an outdated or broken boiler. Though oil boilers are cheap, they can be inefficient during low heating seasons. On the other hand, combination wood and propane boilers operate both combustion chambers so that fuel is burned more efficiently at low outputs. This helps offset the higher cost of propane and increases your home’s overall energy-efficiency. Moreover, the DOA states that, “Burning natural gas, oil, propane, wood, or pellets in your home with a high-efficiency furnace or boiler can be a very efficient way to deliver heat to your home.”
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