20
Encore Woodburning Stove
30003842
Creosote
Creosote is a by-product of slow wood-burning. It’s an
organic tar that can condense in the flue if it’s dense in
the smoke, and slow-moving, and cools off to less than
143° C (290° F). 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 installa-
tion features and operational steps will encourage good
draft and minimize creosote production.
Because letting the smoke cool off and slow down is
one of the keys to creosote production, it makes sense
to line a chimney to match the stove’s outlet size, for
safety reasons as well as performance. Consult a quali-
fied installer and check local and national codes for
recommended chimney size.
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. Fairly ‘green’ wood has a good amount of
moisture in it; it will burn, but some of the heat potential
is used to drive the remaining moisture off the wood.
This reduces the amount that reaches your home and
can contribute to a creosote problem. There are mois-
ture meters available for firewood; you can also judge
your wood by its appearance and weight. 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, especially catalytic ones, the wood
can be too dry. While extra-dry wood has little creosote
in it, the remainder can ‘gas out’ from the wood quickly
and densely enough to overload the catalytic burner.
If you hear a rumbling or roaring noise, like a propane
torch, from the stove, that is a sign the catalyst is seri-
ously overfiring. The catalyst is a platinum film on a
ceramic base; the metal can get to higher temperatures
than the ceramic can take, and overfiring the catalyst
can break it. Dry wood can also burn out faster than
you want. If your dry wood burns out too quickly or
overloads the catalyst you can mix in greener wood to
slow the fire down.
Back-puffing
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 till they’re
dense enough and hot enough to ignite. If your stove
back-puffs, you should open the damper to let the
smoke rise to the flue more quickly, let more air into the
firebox, and avoid big loads of firewood. You should
always see lively, dancing flames in the firebox; a lazy,
smoky fire is inefficient, can lead to back-puffing, and
can contribute to creosote buildup in the chimney.
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 a while 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.
In many cases, local or national codes require the
installation of permanently open air vents, particularly
with larger appliances (i.e. above 5 kW). Refer to these
codes to determine specific requirements for your
installation.
Negative Pressure
Good draft also depends on a supply of air to the stove;
a chimney can’t pull in more air than is available to it.
Sluggish draft results when a house is tight enough to
prevent the ready flow of air to the stove, or by competi-
tion between the stove and other equipment that sends
indoor air outside - especially power-driven equipment
like range hoods, clothes dryers, etc. If the chimney
draws well with all other equipment turned off (or
sealed, in the case of fireplaces and/or other stoves),
then you simply need to be careful with timing the use
of the other gear. If you need to crack a nearby window
or door to enable the chimney to pull well, that’s a sign
that you should install an outside-air intake to bring
combustion air directly to the stove. For most of our
stoves we carry adapters to attach to the stove to con-
nect an air duct for outdoor combustion air.
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 a safe
system.
