Wood is a renewable source of solid energy. Unlike other forms of solid energy such as coal, it is not a nett producer of carbon dioxide, a gas that some people believe is contributing to global warming or other detrimental environmental effects. Burning wood in a wood fire produces no more CO² than allowing the wood to rot in the forest.
Wood is a combination of solid and gaseous components. In order to burn properly, both components must be exposed to proper conditions. "Good wood" is a major contributing factor to the performance of a fire.
The solid component, basically the charcoal content, is the easiest to handle. Most controlled combustion wood firescan extract the heat from this quite readily. This charcoal component generally yields about 50% of the potential heating value of the wood. The gaseous components are harder to burn properly. If not burned properly, these gases can leave the fire as smoke, creosote and particles. Our engineers are now designing fires that extract as much of the usable heat out from the gases emitted by the fuel as possible and, by doing this,so limit the amount of emissions from the flue.
Use dry wood
The most important thing you can do to operate your wood fire correctly is to use the correct fuel.
Most types of seasoned natural wood may be used in your wood fire, but do not use chemically treated wood or wood with high sap content or salt-impregnated wood, such as driftwood. These may corrode the components of the wood fire and flue system. These materials may also emit toxic gases when burnt and will leave toxic residues in the ash and flue.
The moisture content of the wood affects the performance of the wood fire greatly. Well-dried wood is the best thing you can give your wood fire. This should be seasoned for at least 9-15 months to lower the moisture content to less than 25%. Use a Kent Moisture Gauge to measure the moisture content to make sure you are getting the greatest energy from your wood.
Kent wood fires are designed to burn soft wood. Both New Zealand softwoods and hardwoods burn well. Most hardwoods are denser than softwoods and will burn longer for an equal sized piece. All natural woods have approximately the same energy content per unit of dry weight. If hard wood is used as a fuel we recommend that it is mixed piece for piece with soft wood.
Poorly seasoned wood means more work. You will be carrying heavier loads, getting less output per load and your glass door is more likely to get covered in creosote. A wet piece of wood placed in a hot fire will burn but will spit and splutter, even causing water and creosote to be splattered on the glass. While these deposits will burn off, some of the potential performance of your wood fire will be lost. If you can see moisture bubbling off the ends of logs placed in a heater with a good hot ember bed, your wood is too wet.
Fossil fuels such as coal are not suitable. Do not burn garbage, or large quantities of paper, cardboard or similar materials. Do not use wood reclaimed from marshes or swamps. Do not use driftwood.
Use the proper amount of wood
As previously discussed, the best way to see if your wood fire is working properly is by the appearance of the flames. This means that the amount of wood that you use is important.
Wood is stored energy. If you want a large amount of heat to be produced by your fire, you should use a large amount of wood. If you want less energy, use less wood.
IN NORMAL OPERATION, YOU SHOULD NOT ATTEMPT TO REGULATE THE OUTPUT OF THE WOOD FIRE BY USING THE AIR CONTROL, BUT RATHER YOU SHOULD ADJUST THE AMOUNT OF FUEL USED.
On cold days, and when you need a large heat output from your wood fire, load the firebox fully after establishing the fire and you will be comfortable and warm. When comfort levels are reached, subsequent loading should be lesser amounts to maintain the heat level. Optimum efficiency will be achieved when you add only the amount of wood needed until the next time you are free to refuel. Many fires will even burn one log at a time once the stove has been well heated up and a good ember bed exists.
On warmer days, just burn smaller fires (less wood). Make sure you keep the air setting high enough for a clean burn. The cleanest burns will occur when large pieces of wood are placed on a good bed of glowing coals and the wood fire itself is at a high temperature.
Use wood of different sizes and shapes to promote good air flow around the pieces. You can load up to 2/3 the height of the firebox chamber. Avoid over-firing. If the top of the firebox is glowing, you are over-firing. This will damage the wood fire. Store your ready-to-use firewood well away from the wood fire while it is in use.
Preparing/storing wood for burning
To get the best possible heating value out of your wood, you will need to season it properly. This is best accomplished by planning ahead. Wood can take up to two years to dry out fully. A fresh cut tree can be up to 50% water, which means half of the weight of the log you are carrying is of no use to you. If stored well, after 12 months of seasoning, the moisture content may have dropped to between 10 and 20%, which will be ideal for getting the best performance out of your wood and fire.
The shorter the piece of wood and the greater the surface area exposed to the air, the faster it will dry. A good way to prepare your wood is to cut it to heater-sized lengths and split any pieces over 150mm (6 inches) diameter as soon as the tree is felled.