Building Different Fires For Different Needs - HearthStone WFP-75 Owner's Manual

The fireplace can operate at three different
settings: Maximum combustion rate, medium
combustion rate and low combustion rate.
As the air intake is reduced, the burn rate
decreases. This has the effect of distributing the
thermal energy of the fuel over a longer period
of time. In addition, the flow rate of exhaust
through the appliance and flue pipe slows down,
which increases the duration of the energy
transfer of the exhaust gases. As the air intake
is reduced, the flame slows down.
If the flames diminish to the point of
disappearing, the air intake has been reduced
too early in the combustion cycle or the wood
used is too wet. If the wood is dry and the air
control is used properly, the flames should
decrease, but remain bright and stable.
On the other hand, too much air can make the
fire uncontrollable, creating very high
temperatures in the unit as well as in the
chimney and seriously damaging them. A
reddish glow on the unit and on the chimney
components indicates overheating. Excessive
temperatures can cause a chimney fire.

4.3.8 BUILDING DIFFERENT FIRES FOR DIFFERENT NEEDS

Using the air control is not the only way to match the fireplace's heat output to the heat demand. Your
house will need far less heat in October than in January 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 fireplace down so much that
the fire will be smoky and inefficient. Here are some suggestions for building fires to match different heat
demand.
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 3" to 4" 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 tend the fireplace and should provide enough heat for four
hours or more. Small fires like this are a good time to use softer wood species so there will be less chance
of overheating the house.
LONG LASTING LOW OUTPUT FIRES
Sometimes you will want to build a fire to last up to eight hours, but don't need intense heat. In this case
use soft wood species and place the logs compactly in the firebox so the pieces are packed tightly
together. You will need to fire the load hot for long enough to fully char the log surfaces before you can
turn the air down. Make sure the fire is flaming brightly before leaving the fire to burn.
HIGH OUTPUT FIRES FOR COLD WEATHER
When the heat demand is high during cold weather, you'll need a fire that burns steadily and brightly. This
is the time to use larger pieces of hardwood fuel if you have it. Put the biggest pieces at the back of the
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HearthStone Quality Home Heating Products, Inc ® WFP-75 Model 8411