Outdoor wood-fired boiler

The outdoor wood boiler is a variant of the classic wood stove adapted for set-up outdoors while still transferring the heat to interior buildings.

Technology

The outdoor wood boiler is a variant on the indoor wood, oil or gas boiler. An outdoor wood boiler or outdoor wood stove is a unit about 4-6 feet wide and around 10 feet long. It is made up of three main parts, the firebox, which can be either round or square, the water jacket, and the exhaust heat reclaiming system. The fire box ranges from 2 to 5 feet long and can be as tall as 4 feet. It is fit lengthwise inside the outer shell and is surrounded by the water jacket. The water Jacket is a second shell around the fire box which is filled with water, which is circulated through insulated underground lines to the house, where the heat can be transferred from the water to the existing heating system. After the wood is burned, the smoke is passed through the water jacket to reclaim much of the heat in the exhaust. Many companies now manufacture various models. Several such manufacturers are Heatmaster SS, Heatmor, Central Boiler, Portage and Maine, Crown Royal, Taylor, Woodmaster, Hawkin, American Royal and many more.

Standard outdoor wood boilers

Standard outdoor wood boilers heat the firebox and the smoke goes out the exhaust straight. If not run hot enough, the exhaust gas will be thick and black, and the resulting ash will not be fully rendered.[1] While functional, these models take more work and are far less efficient[2] than some newer more efficient models.

Catalytic outdoor wood boilers

Some newer outdoor wood boilers have a catalytic converter installed, to allow for a more efficient burn and treatment of the exhaust before it leaves the unit. There is a considerable difference in cost between these and standard units.[1]

Secondary combustion wood boilers

There is a new breed of wood boilers that use naturally occurring secondary combustion to burn additional wood gases. The most sophisticated systems use computer controls to direct air at different stages of the burn process at variable volume.

Opinion: Outdoor wood boilers are a topic of environmental controversy.[3] An improperly used or built outdoor wood boiler can produce great amounts of wood smoke and waste material. There are efforts among governments, citizens, and manufacturers to try to ensure that the technology is produced and regulated right while it is still in relative infancy.

One of the largest problems now is that there are no one set of standards regarding the manufacture of outdoor wood boilers or their allowed emissions. In the United States, the EPA has established a voluntary program to qualify outdoor wood boilers that meet certain emission standards.[2] However, as of February 2012, in the United States only 8 states have adopted this voluntary standard and only allow the installation of these cleaner, EPA qualified outdoor boilers.[2][4] Two states — Washington and Oregon — effectively ban them altogether. The EPA is in the process of making new regulations and will establish a national standard that all outdoor wood boilers have to be certified to meet emission standards.[2]

The only truly effective test that exists now is to measure the plume data of the chimney exhaust.[5] Currently, very few outdoor wood boilers have been submitted to this test, making it harder for the consumer to make informed environmental choices.

See also

References

Sources

External links

http://outdoorwoodfurnaceinfo.com