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The Differences Between a Wood Boiler, a Wood Burning Stove and a Gas Boiler
How does a wood burning boiler stove (or more commonly and shorter, a wood boiler) differ from a (or traditional wood burning stove) or a conventional oil or gas boiler?
The central and obvious difference between a wood burning stove and a wood boiler is the addition of a metal box containing water that uses heat from the wood burner to heat that water, which is then piped to household radiators and/or stored in a hot water cylinder for washing and so on. A wood stove boiler differs from a normal oil or gas boiler simply by virtue of the fact that it burns wood to produce heat with which to heat water.
For the record, the term boiler has its origins in the Steam Age of the Industrial Revolution, where water was indeed heated to boiling point in order to produce steam to power pistons and the like. Modern boilers do not in fact boil water and typically have safety devices to prevent this happening. Water heated in a “boiler” is typically in the range 50 to 70 degrees centigrade.
As ever in the world of wood burning appliances, there is a bewildering variety of styles, sizes and makes of wood burner to
confuse you choose from. Some look very much like the traditional woodburner – black metal with a glass window – we’re all familiar with while others more closely resemble a conventional gas boiler.
The differences in aesthetic styling are usually a function of the intended purpose and location of the wood boiler. If it is to be installed in a main room, say the lounge, then it is probable that it will also be required to provide space heating and to look like a typical wood burner stove.
If on the other hand the wood boiler is purely for the utilitarian purpose of heating water for radiators and bathing then most people prefer that it be fitted in a kitchen or utility room and that the wood boiler conforms to the expected outward appearance of a normal gas boiler.
How a Wood Boiler Works
Regardless of the apparently endless permutations in looks though, all wood boiler stoves perform the same function the same way by transferring heat from the wood burning stove to water in the “boiler”, which is then pumped to heat radiators or stored as domestic hot water.
The boiler is, as noted above, nothing more complicated than a water-filled metal box with a number of what are called “tappings” that permit water pipes to be attached. Obviously there is at least one input, providing cool water and one output for the heated water to flow away once it becomes hot enough (but before it actually boils). A common design of wood boiler involves replacing the firebricks that insulate the back of the firebox with the boiler itself – these being termed wood burning back boilers for self-evident reasons.
Connecting wood burner stoves to the household heating system is little different to installing conventional gas boiler systems, but even if you are capable of installing a conventional heating system you would still be well advised to consult a heating engineer experienced with wood boiler systems.
But in principle, connect an output tapping to the domestic radiator feed pipe and connect the radiator return pipe to an input tapping. If using under floor heating then you need to connect the wood boiler to a hot water tank (quite commonly an “accumulator” tank capable of keeping a large quantity of water hot for extended periods) and connect the underfloor heating system to the tank.
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