Wood needs to be stored for two reasons, firstly it would be impracticable to fell a tree whenever the stove needed lighting and secondly, wood as a living plant, contained water which is the last thing we should be trying to burn. Storing wood to dry may be tedious but it costs nothing and you will be rewarded with a stove that operates safely, attractively and more economically.
During combustion chemicals are broken apart and are reformed differently. The two prominent ones being formed are carbon dioxide, which is being formed constantly, and water, which is being formed when the volatile gasses are burning. This water is produced within the flame in the form of steam and within a properly running stove and lined flue this should remain as a vapour until venting into the atmosphere and cause no problems. It will only become a problem when the stove is run at a very low setting and the flue is allowed to cool, when the water vapour will condense on the flue walls. The Plexus was designed to burn off the volatiles first, when the stove is operating normally and the temperature of the flue will be at its hottest, leaving the charcoal, which does not make water, to be used for very slow burning.
No stove has ever been designed to burn wet wood because burning wet wood is a waste of energy and potentially dangerous. The loss of energy when burning wet wood is usually given as the amount of heat needed to heat and boil off the water from the wood. Given that a loading of wet wood will contain a kettle full of water, the energy lost will be all too apparent to anyone who has waited for a kettle to boil will realise that boiling a kettle dry would use a considerable amount of energy. Unfortunately, the energy used boiling off water is only the easily calculated heat loss, to make a quantitative prediction of the heat lost because of the affect the steam and water vapour has on the combustion of the volatiles is impossible.
Water is a far better conductor of heat than wood and so putting a wet log onto a fire immediately cools both the space in which the volatiles are burning and the fire beneath. Putting several wet logs on the fire may reduce temperatures to the point were some of the volatiles’ temperatures are reduced below their ignition temperature and extinguish. Volatiles impinging against the cold wet logs will certainly be extinguished.
Water is such a good conductor of heat that it is possible to boil water in a paper bag over a flame
because the water conducts heat away from the paper, keeping it below its ignition temperature.
Do not attempt to do this experiment yourself.
What happens to the wet log as it heats up is yet more wasted heat. As the outer layer of wood begins to warm it will begin to emit volatiles but behind the volatiles will be more steam and water vapour being driven
from the wood.
Water in a true vapour form, rather than a mist of water droplets, is water that is invisible, has expanded up to one and a half thousand times its original volume and contains no air. Not only will this be mixing with the volatiles to prevent them reaching ignition temperature it will also prevent air from being able to mix with them if they are heated sufficiently elsewhere in the stove. The heat loss of these supplementary effects of water on the combustion are will vary and are incalculable but they are significant.
Because the stove is being cooled with water it will never reach its operating temperature and will allow some of the unburned volatiles to condense back onto the stove’s glass as a dark brown tar. Those unburned volatiles that escape both the stove and the flue will do so as smoke. Almost all smoke is visible proof that the stove is allowing fuel to escape and provides you with a simple guide as to how well you are operating the stove. You might argue that if it is cold enough to have lit the stove it is too cold to stand outside watching the chimney pot for the sake of a little efficiency but it is not just efficiency, it is your ecological responsibility to make the best use of natural resources and not be a cause of pollution.
Having discussed efficiency we move on to the safety aspects of burning wet wood. If you were to boil pans of water on the stove top you would expect to find the room becoming very damp and by burning wet wood the flue will become similarly wet, allowing undesirable conditions to develop. Firstly the gasses entering the flue are cooler than they should be and because the temperature difference between the flue way and outside air is reduced the flue gasses will travel slower causing an already struggling stove to be operating with reduced draught.
Detailed information about seasoning wood
