Today’s Wood Stove – High Efficiency & User Friendly
A wood stove means different things to different people. Some think of it as ambiance – a romantic setting with the warm glow of the flame. Some make a hobby of cutting and tending the wood with the added benefit of healthy exercise. Still others view it as function – a means of heating the majority of the home. As great technological advances have positively affected home design, construction and appliances, the same is true with the wood stove.
By 1990 negotiations between the US Environmental Protection Agency (EPA) and the hearth industry resulted in lower emission standards for wood stoves – from 40 grams per hour to less than 6 gph. For EPA approval, manufacturers were forced to build a better stove. From that evolution, today’s wood stoves burn much cleaner and produce more efficient heat from a smaller firebox size. This also results in longer burn times. To understand how these benefits occur, some explanation of wood combustion is helpful.
Wood combustion is a complex physical-chemical process during which hydrogen and carbon in the fuel are chemically combined with oxygen to form combustion products and to release heat. This takes place in the four stages of combustion.
Stage 1: Moisture Evaporation – when wood is heated, contained moisture evaporates to form steam. In this stage, heat is absorbed, not given off.
Stage 2: Vaporization of Hydrocarbon Compounds – the chemical structure of the wood molecules begin to break down and hydrocarbons begin to vaporize. This vapor contains hydrocarbons in the form of liquid droplets (creosote) and other combustible gasses such as methane, carbon dioxide, carbon monoxide, and other combustible and non-combustible gasses. Heat is still being absorbed, not being given off.
Stage 3: Gas Vapor Ignition and Combustion – in this stage, the gasses mentioned in stage two are burned by injecting oxygen at the ceiling level of the stove, greatly reducing the emissions by about 85% and turning them into heat at the same time. In short, you’re efficiently burning your smoke!
Stage 4: Char Burning – basically the carbon in the charcoal is the only remaining combustible material. Charcoal burns with little or no flame and produces temperatures in excess of 1100° F. Stages three and four are the heat-producing stages. In the case of the older non-EPA stove, you don’t get the advantage of stage 3.
There are EPA exempt stoves still being sold in discount stores and farm stores. They are exempt because they are burning at a fuel to air ratio above 35 to 1. The characteristics of these non-EPA stoves are incomplete combustion resulting in hazardous creosote buildup, excessive fuel consumption and generally shorter stove life. They are cheaper up front but costlier in the long run.
The best advanced-combustion stoves or high-tech stoves have a single lever air control for easy operation. This lever is used to control the burn rate of the wood and heat output. The stove itself has an air manifold that injects a measured amount of air into the firebox. This supports the secondary combustion, main combustion, and the air wash for a clean viewing glass. It also provides the boost air at the base of the fire for speeding up the combustion process. These quality wood stoves have another important advantage. They are simpler to operate than a non-EPA wood stove.
As important as your choice of a high-tech wood stove, is your choice of the chimney pipe and overall installation. Any airtight wood stove depends on air being pulled through it to inject oxygen, fueling the fire. This is accomplished through the proper draft of the chimney. Wood burning experts agree that the chimney is the engine that runs the stove. A properly designed chimney, using high quality components and installed by an expert is your only assurance of the proper and efficient operation of your modern EPA wood stove.
It’s the complete system and expert installation you need to evaluate. To see these stoves burning and discuss options for freestanding stoves or wood burning inserts, stop by or call your NFI certified wood burning specialist today.