Osburn Soho Installation and Operation Manual
_______________________________________________________________________________19
Although it is important to fire each new load hot to prepare for a clean burn, do not allow the fire
to burn at full intensity for more than a few minutes.
DO NOT LEAVE THE WOOD FIRE UNATTENDED WHILE A NEW LOAD IS BEING FIRED HOT.
When you burn a new load of wood hot to heat up the wood, the wood fire and the flue system,
the result will be a surge of heat from the wood fire. This heat surge is welcome when the room
temperature is a little lower than desirable, but not welcome if the space is already warm.
Therefore, allow each load of wood to burn down so that the space begins to cool off a little
before loading. Letting the space cool before loading is one of the secrets to clean burning and
effective zone heating.
4.3.5
TURNING DOWN THE AIR SUPPLY
Once the firewood, firebox and flue system are hot, you can begin to reduce the air supply for a
steady burn.
As you reduce the air supply to the fire, two
important things happen. First, the firing rate slows
down to spread the heat energy in the fuel over a
longer period of time. Second, the flow rate of
exhaust through the wood fire and flue slows down,
which gives more time for the transfer of heat from
the exhaust. You will notice that as you reduce the air
setting, the flames slow down. This is your indication
that the wood fire is burning at its peak efficiency.
If the flames get small and almost disappear when
you turn down the air, you have turned down the air
too early, or your firewood is wetter than it should
be. With good fuel and correct air control use, the
flames should slow down, but should stay large and
steady, even as the air supply is reduced.
4.3.6
BUILDING DIFFERENT FIRES FOR DIFFERENT NEEDS
Using the air control is not the only way to match the wood fire’s heat output to the heat demand.
Your house will need far less heat in April than in July to be kept at a comfortable temperature. If
you fill the firebox full in fall weather, you will either overheat the space or turn the wood fire
down so much that the fire will be smoky and inefficient. Here are some suggestions for building
fires to match different heat demand.
4.3.6.1
Small Fires to Take the Chill Off the House
To build a small fire that will produce a low heat output, use small pieces of firewood and load
them crisscross in the firebox. The pieces should be only 75 mm to 100 mm in diameter. After
raking the coals, you can lay two pieces parallel to each other corner to corner in the firebox and
lay two more across them in the other direction. Open the air control fully and only reduce the air
after the wood is fully flaming. This kind of fire is good for mild weather when you are around to
