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OPERATING HINTS
To get the best from your Kemlan heater it is essential that you use good firewood, and use it correctly Many people do not understand the
principle of using a w ood burning appliance and w e suggest that it w ill be w orth your while to study the follow ing extract fr om a w ell know n
American publication.
PRINCIPLES OF COMBUSTION: HOW WOOD BURNS
Technically, w ood does not burn. What burns is the volatiles and charcoal that are created. That is w hy wood will not catch on fire
immediately w hen you put a match to it; it has to first undergo the chemical changes that create the volatiles, and a match does not create
enough heat to activate the process. As kindling and paper evaporate the moisture in the w ood, the w ood absorbs heat. At a certain point,
gases are given off and w hen these volatiles reach 480 degrees F, or the "Flash point", as it is called, they w ill burst into flame if sufficient
oxygen is present. The volatiles give off more heat than does charcoal, w hich is w hy a fire w ith flames (which burn the volatiles) produces
more heat than one that is all charcoal.
Since the volatiles are gases and since heat rises, taking the gases w ith it, it is very easy to create a situation in w hich most of the volatiles go
up the chimney almost as soon as they are produced. This is w hat happens with a roaring fire and, to a lesser extent, w ith an open fire. One of
the reasons (but only one) that a freestanding w ood stove produces more heat than an open fire is that the volatiles are cont ained w ithin the
firebox and are not so quickly dissipated up the chimney. A stove that is baffled is merely one that has interior construction design to keep the
volatiles in the firebox longer; the longer they are in the firebox, the more completely they burn. The more completely they burn, the more heat
is produced. It's that simple.
Since the flames burn the volatiles and produce heat, the ideal situation is the longest possible flame path. As soon as w ood burners
understand this, they tried to devise w ays of making the flame path longer than in an ordinary open fire. Even though the role of oxygen in
combustion w as not under- stood in Ben Franklin's time, Franklin did realize the importance of more completely burned volatiles. His solution
w as to try to invent a dow ndraft stove
– one that sent the volatiles back dow n through the fire – but he never succeeded in getting it to w ork. A dow ndraft goes against the nature of
volatiles, w hich is to rise. In more recent times, there have been some successful downdraft – or partial dow ndraft – stoves created and some
of the fireplace stoves and units utilise this principle. Ideally, it w ould be best if the volatiles could be redirected dow n through the fire several
times, until they w ere al- most totally consumed. This w ould not only make the maximum use of the heat potential of the w ood; it w ould reduce
creosote build-up to almost zero. Perhaps someday an ingenious inventor w ill design a unit that does this; so far no has been able to.
MOISTURE AND COMBUSTION
As w e have seen, dry wood ignites faster and burns better – w ith higher heat production – than w et or green w ood. The difference between
the amount of heat produced by dry w ood and green w ood is so great that a dry softwood of good grade w ill produce more heat than green
hardw ood. Green w hite ash, for instance, is not as good a fuel as dry tamarack.
The reason for the superiority of dry w ood is easy to understand. Heat cannot be produced until moisture has been driven off. Since even so-
called seasoned dry w ood contains approximately 20 percent moisture, it takes time for any fire to begin producing useable heat. Wet w ood,
w hich can have a moisture content of over 100 percent (due to the w ay moisture is measured), w ill take that much longer to pr oduce heat.
Meanw hile, the fire w ill produce smoke and creosote and very little heat. This w as brought sharply to my attention w hen I installed my first
w ood heater. To my surprise and delight, I found it comfortably heated eight rooms, w here I had expected to heat only tw o or three. After
some time, w hen I had someone helping me run the fire, I suddenly noticed that the house w as chilly. We added more w ood and adjusted the
draft controls, but nothing w e did seemed to help. It finally occurred to me to check the w oodpile. My friend had been getting green w ood from
a stack that w as drying, instead of from the dry-wood stack. The difference the green w ood made w as so dramatic I w ill never for get it.
HOW TO TEST WOOD FOR DRYNESS
There are tw o easy ways for even a novice to spot dry w ood. Dry w ood tends to "check". Look at the log ends and you w ill see cracks radiating
from the centre of the log. If the logs have been split, the cracks w ill be harder to find because w ood tends to split along the cracks.
Another test for dry w ood is the sound it makes w hen two logs are banged against each other. Green w ood will make sort of a dull thud; dry
w ood makes a nice crisp, sharp sound. Once you have heard the tw o, you w ill remember the difference.
FROM THE ABOVE EXTRACT SEVERAL FACTS BECOME APPARENT:
1. It is vital that your firewood be dry and seasoned.
2. A good hot fire of kindling and smaller pieces of fuel must be established before adding larger logs.
3. The larger logs should be w ell alight before slow ing down the combustion by adjusting the air intake.
4. A hot bed of coals needs to be maintained to ensure continued combustion in the firebox.
5. When new timber is added to the firebox the air control should be opened until the fuel is w ell alight before damping it dow n again. This w ill
take from 10 to 20 minutes.
6. When setting the controls for overnight burn you w ill need to experiment w ith the settings to suit your particular type of fuel. Very dense
hardw ood requires more air to combust and over damping w ill result in charring and smoking causing the glass in the door to become dirty.
The same w ill apply w ith fuel w hich is not fully seasoned or is not dry enough. Kemlan have follow ed a policy since 1969 of c hecking on all
complaints about poor performance of their heaters and apart from a few instances of incorrect installation (mostly insufficient flue length) all
problems have been directly related to incorrect operation and/or poor fuel. We know you w ill experience many years of satisf action from your
heater if you follow the above advice.
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