As a final note, the four basic stages of wood burning are:

a)Up to 212o F the wood is boiling of the moisture.

b)Near 575o F gasification of the solid wood fuel occurs. The wood will simply seem to disappear. Very little energy is released in these first two stages and external energy must be applied to sustain any combustion that is occurring.

c)Somewhere between 900o F and 1100o F the wood fuel particles have combined with oxygen molecules and released the majority of the available energy. Some gases will still not have reached ignition temperature and at this critical stage, if too much heat is removed from the combustion chamber, no more fuel will be burnt. All remaining fuel will simply exhaust through the system as unburned material.

d)At temperatures around 1500o F the remaining gases and tars will burn off in the combustion chamber. This final combustion yields an additional 10 to 20% additional heat energy and gives a very clean final exhaust from the product.

Wood pellets, as compared to wood logs, enhance the amount of energy released during the burn cycle because of the uniformity of product, the reduced moisture content, and the variation in materials used to produce the wood pellet. These variations allow the turbulence in the burn system to ensure a better agitation of fuel with air and a more rapid and efficient burn. As other biomass fuels are utilized, optimum mixes of pellets will ensure clean burning, reduced emission system are available that compete favorably in the consumer market.

The service technician must be aware that as technology evolves, all stove manufacturers will strive to control more of the variables that might adversely affect the combustion process. In addition, stove manufacturers will strive to optimize the efficiency of the products burn process. It is the service technician’s responsibility to understand not only the particular product but also how environmental issues beyond the control of both the manufacturer and the service technician can affect a product’s burn process. This understanding will make trouble diagnosis less time consuming and more accurate for all parties involved in maintaining the product in a reliable manner to the satisfaction of our mutual customers.

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