Vermont Castings • Dauntless FlexBurn Owner’s Manual_R3 • 2020 - ___ • 05/20
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Draft Testing
An easy way to test your chimney draft is to close the stove’s
damper, wait a few minutes to let the airflow stabilize, then see
whether you can vary the strength of the fire by swinging the
air control open and closed. Results are not always instant;
you may need to wait a few minutes for a change in the
air control setting to have an effect on the fire. If there’s no
change, then the draft isn’t strong enough yet to let you close
the damper, and you’ll need to open it for awhile longer and
manage the fire with the air inlet until the draft strengthens.
If you keep track of your burning habits and relate them to
their effects on the stove’s operation, you’ll be rewarded with
good performance and a safe system.
Conclusion:
Wood-burning is an art rather than a science.
Once the stove and chimney system are in place, you can
only vary your technique, mostly your timing, to achieve good
results. If you keep track of your burning habits and relate them
to their effects on the stove’s operation, you’ll be rewarded
with good performance and years of reliable heating.
H. Important Information
Creosote
is a by-product of slow wood-burning. It’s an
organic tar that can condense in the flue if it is present in the
exhaust, slow-moving, and cools to less than 290°F (130°C).
Condensed creosote is volatile, and can generate chimney
fires if it gets hot enough. All the features that affect chimney
draft also affect creosote condensation - so use whatever
combination of installation features and operational steps that
will encourage good draft and minimize creosote production.
Because letting the exhaust cool off and slow down is one of
the keys to creosote accumulation, it makes sense to line a
chimney to match the stove’s outlet size, for safety reasons
as well as performance. Canadian law requires a matching
liner to serve any stove or insert vented through a fireplace
chimney; in the US, the National Fire Protection Association
(NFPA) recommends a chimney liner if the flue is more than
three times bigger (in square area) than the outlet on the
stove or insert. Some localities enforce the NFPA guidelines
as part of their building codes.
Fuel:
Even the best stove installation will not perform well
with poor fuel. The best fuel is hardwood that has air-dried
12-18 months. Softwood burns, but not as long as hardwood.
‘Green’ wood contains a lot of moisture; it will burn, but some
of the heat potential is used to boil the extra moisture from
the wood. This reduces the amount of heat that reaches your
home and can contribute to a creosote problem. There are
moisture meters available for firewood; you can also judge
your wood by its appearance and weight (Moisture content
of 20% or less is best). If you get it green, lift a piece and get
a sense of its weight; it can lose a third or more of its weight
as it dries. Also look at the ends of a log; as it dries it shrinks
and often cracks. The more weathered and cracked a piece
is, the drier it is.
Dry wood burns readily with a good chimney draft. But with
modern stoves, wood can be too dry and too volatile. Smoke
and combustible gases can ‘gas out’ from the wood quickly
and densely enough to overload the combustion system. If
you hear a rumbling or roaring noise (like a propane torch)
from the stove, that is a sign that the stove is over-firing.
Back-puffing
results when the fire produces volatile gases
faster than the chimney draft pulls them out of the firebox.
The gases back up in the firebox until they are concentrated
enough and hot enough to ignite. If your stove back-puffs,
the stove needs to cool down. You should open the damper
to let the smoke rise to the flue more quickly, allow more air
into the firebox, avoid big loads of firewood and check that
the wood moisture is not too low.
