Vermont Castings Savannah SSI30 Owner's Manual page 10

SSI30 Wood Insert
It is common for a masonry flue to be oversized for the
insert. Such a chimney can take quite a while to warm up,
and the insert performance will likely be disappointing. The
best solution to an oversize flue problem is the installation
of an insulated steel chimney liner of the same diameter
as the appliance flue outlet. The liner keeps the exhaust
gas warm and the result is a stronger draft. An uninsulated
liner is a second choice—although the liner will keep the
exhaust restricted to its original volume, the air around the
liner will require time and heat energy to warm up.
Check your local codes. You may be required to install a
flue liner in any oversize masonry flue.
Masonry Chimney
Although masonry is the traditional material used for
chimney construction, it can have distinct performance
disadvantages when used to vent a controlled combustion
wood insert. Masonry forms an effective "heat sink"—that
is, it absorbs and holds heat for long periods of time.
The large mass however, may take a long time to become
hot enough to sustain a strong draft. The larger the
chimney (in total mass) the longer it will take to warm up.
Cold masonry will actually cool exhaust gases enough
to diminish draft strength. This problem is worse if the
chimney is located outside the home or if the chimney
flue has a cross-sectional volume much larger than the
insert outlet.
10
pipe and 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 insert
through completely straight chimney. Use this layout if at
all possible, as it will promote optimum insert performance
and simplify maintenance.
If the insertpipe must elbow to enter a chimney, locate
the elbow about midway between the inserttop 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 insert pipe
between the insert and a chimney. Longer runs can cool
the smoke enough to cause draft and creosote problems.
Use double-wall insert pipe for longer runs.
Single venting
Your insert requires a dedicated flue. Do not connect the
insert to a flue used by any other appliance. Chimney draft
is a natural form of energy and follows the path of least
resistance. If the insert is vented to a flue that also serves
open replace or another appliance, the draft will also pull
air through those avenues.
The additional airflow will lower the flue temperatures,
reduce draft strength and promote creosote development;
overall insert 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 appliances can even impose
a negative draft and result in a dangerous draft reversal.
ChIMNEY ClEARANCES
63D4004