Vermont Casting 1450 - Manual (Page 27)

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Encore 1450 Non-Catalytic Woodburning Stove
30002425
Creosote
Creosote is a by-product of slow wood-burning. It is an
organic tar that can condense in the flue if the exhaust
gases cool too much. Condensed creosote is volatile,
and can fuel chimney fires if it gets hot enough. All the
factors that affect chimney draft also affect creosote
condensation - so use installation features and opera-
tional steps that 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. Canadian law
requires a matching liner to serve any stove or insert
vented through a fireplace chimney; in the US, the Na-
tional Fire Protection Association recommends a liner if
the chimney is more than three times bigger (in square
area) than the outlet on the stove or insert. Some locali-
ties enforce the NFPA guidelines as part of their build-
ing 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 and is stored, covered from the
elements. Softwoods burn well, but not as long as hard-
wood. ‘Green’ wood has more moisture in it; it will burn,
but more of the heat from the fire is needed to drive the
extra moisture off 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 ap-
pearance 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.
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 until they
are dense enough and hot enough to ignite. If your
stove back-puffs, you should open the damper to direct
more heat up the chimney to allow the smoke to rise
to the flue more quickly, let more air into the firebox.
Smaller loads of wood, larger pieces of wood and
avoiding overly dry wood loaded into a very hot stove
may help this problem. If back-puffing persists, contact
your dealer or qualified chimney sweep to help diag-
nose the problem.
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.
Test chimney draft with a draft gauge.
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 com-
petition between the stove and other equipment that
removes air from the house - 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 equipment. 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, adapters are available to connect
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.