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Aspen Woodburning Stove
30000369
Pipe & Chimney Layout
Every bend in the flue will act as a brake on the exhaust
as it flows from the firebox to the chimney cap. The
ideal pipe and chimney layout is straight up from the
stove through a completely straight chimney. Use this
layout if at all possible as it will promote optimum stove
performance and simplify maintenance.
If the stovepipe must elbow to enter a chimney, locate
the elbow about midway between the stove top and
the chimney thimble. This configuration lets the smoke
speed up before it must turn, keeps some pipe in the
room for heat transfer, and allows long-term flexibility
for installing a different appliance without relocating the
thimble.
There should be no more than eight feet of single-wall
stove pipe between the stove and a chimney. Longer
runs can cool the smoke enough to cause draft and
creosote problems. Use double-wall stove pipe for
longer runs.
Single Venting
Your stove requires a dedicated flue. Do not connect
the stove to a flue used by any other appliance. Chim-
ney draft is a natural form of energy and follows the
path of least resistance. If the stove is vented to a flue
that also serves an open fireplace or another appliance,
the draft will also pull air in through those avenues. The
additional air flow will lower flue temperatures, reduce
draft strength and promote creosote development; over-
all stove performance will suffer. The effect is similar
to that of a vacuum cleaner with a hole in the hose. In
some extreme instances, the other appliance can even
impose a negative draft and result in a dangerous draft
reversal.
Fuel
Even the best stove installation will not perform well if
poor fuel is used. I available, always use hardwood that
has been air-dried (‘seasoned’) 12-18 months. Soft-
wood burns more rapidly than hardwood and has a high
resin content conducive to creosote production. De-
cayed wood of any type has little heat value and should
not be used.
All unseasoned (‘green’) wood has a high moisture con-
tent. Much of its heat value will be used to evaporate
moisture before the wood can burn. This significantly
reduces not only the amount of energy available to
warm your home, but also the intensity of the fire and
temperature of the exhaust gas. Incomplete combustion
and cool flue temperatures promote creosote formation
and weak draft.
You can judge the moisture content of wood by its ap
-
pearance and weight or use a commercially available
moisture meter for an exact measurement. Unseasoned
wood will be a third heavier than dry wood. Also, look
for cracks (‘checking’) in the ends of the log that result
from contraction as the wood dries. The longer and
wider the cracks, the dryer the wood is. Purchase your
fuel from a reputable dealer.
Creosote
Creosote is a by-product of low-temperature stove
operations, weak draft or both. It is a tar that results
when unburned gases condense inside the flue sys-
tem at temperatures below 290°F. Creosote is volatile
and can generate chimney fire. All of the installation
characteristics that adversely affect chimney draft also
promote creosote condensation. Consequently, you can
minimize creosote accumulation with an effective chim-
ney design and the use of operational techniques that
encourage good draft and complete combustion.
Backpuffing
Backpuffing is a condition that results when the draft is
too weak to pull flue gases out of the chimney system
as fast as the fire is generating more. Volatile gases
build up within the firebox until reaching a density and
temperature at which they ignite. With this ignition, you
may hear a muffled popping sound and see a bit of
smoke forced out of the air inlets.
This condition is most likely to occur in the spring or fall
when moderate outdoor temperatures and low inten-
sity fires combine to inhibit draft strength. If your stove
backpuffs, open the damper to let the smoke rise to the
flue more quickly. Also, open the air inlets to induce a
livelier fire and speed airflow through the stove. Avoid
large loads of firewood at one time. You should always
see lively, dancing flames in the firebox; a lazy, smoky
fire is inefficient and will promote draft problems.
Draft Testing
An easy way to determine whether your chimney draft
is strong enough is to close the stove damper, wait a
few minutes to let the airflow stabilize, and then test
whether you can vary the strength of the fire by swing-
ing the air control open and closed. Results here are
not always instant; you may need to wait a few minutes
for a change in the air control setting to have an ef-
fect on the fire. If there is no change, the draft is not
yet strong enough to let you close the damper. You will
need to open it for awhile longer and manage the fire
with the air inlet until the draft strengthens. Keep a re-
cord of your operational habits and relate them to their
effects on the stove’s function. You will be rewarded
with safe and efficient performance.