9
fore lighting the stove each time to prevent the gradual build up of
deposits.
Small, hot fires are more efficient than large slumbering fires. Most
of the energy in burning wood is released as a bright flame. The tur-
bulence in the flames creates good mixing between the combustion
air and the gases that are released from the wood as it heats up. The
heat of the fire ignites and burns these gases. In contrast, the dense
smoke from a slow, smouldering fire is potential heat energy that es-
capes up the chimney and either clings to the chimney flue as creo-
sote or pollutes the outdoor air. Therefore, to gain the most heat from
each load of firewood, the wood should be flaming throughout the
burn cycle until it is reduced to ash.
If you do a fair bit of slow wood burning, it is good practice to burn a
good, hot stove at regular intervals to keep your chimney dry and
prevent the build up of tar.
When refuelling, place wood towards the back of the stove where it
will burn hotter and more efficiently. Try to place logs length ways
so that any spitting from the end grain does not go onto the glass
window. The fuel should not be stacked higher than the top of the
back fire brick. Once the stove is hot and running steady, it should be
possible to maintain the nominal output by refuelling approximately
once an hour.
Notes on wood burning
Wood burns most efficiently when the air for combustion is supplied
from above the fire bed rather than below. The air supplied above the
fire bed provides the oxygen necessary for the volatile gases
(smoke), given off by the wood as it heats, to combust. This ensures
that the gases are burnt and used to heat the appliance instead of be-
ing wasted up the chimney or condensing and forming tarry deposits
inside the stove, the flue pipe or on the door glass. Running the
stove with only the bottom air control open in a Vesta stove does not
supply air to the base of the fire but adds oxygen to the top of the fire
at the back of the stove. This helps to draw the fire into the back of
