No Draw/Insufficient Draw
Type of Stove?
of woodstoves have different needs as far as draw is concerned. Old
fashioned stoves which were not designed to be as efficient as newer
models would generally work well even with a weaker draw, newer
technology brought on by increased demand by the environmental
protection agency to produce cleaner burning woodstoves, as well as the
demand for more efficient use of wood fuel have brought about the
development of units which will burn wood with a high output while
giving a longer burn time and lesser emissions produced. These units
require a stronger draw as the features that make the unit burn more
efficiently create resistance to the pull of the chimney.
Type of Chimney?
The type of chimney used can have some bearing on what to look for
when draw is not present. The two types of chimneys used would be a
masonry (brick) chimney, and the premanufactured (pipe) chimney. The
masonry chimneys usually have "clean out" doors at the bottom of the
flue. This door would not effect function of older type stoves as they
do not create the resistance mentioned above, but the newer type stoves
do so and what happens is the chimney (which will pull from the path of
least resistance) will start to pull air through that clean out door as
well as any other air leaks in the flue or the stovepipe. This reduces
the amount of air pulled through the stove itself, causing the fire to
die when the door to the stove is closed. The premanufactured kit
chimney in some configurations will have a "clean out Tee"
if the chimney is run through the wall and up, the cap at the bottom of this
tee should have an airtight seal as well. Another common problem when
using a premanufactured chimney concerns the installation, if the chimney
is not installed with sufficient height as well as the proper
(see above) the flue will not generate enough draw to operate the unit.
Houses these days are generally built to hold heat much better than in
years past. This is obviously a good thing as it lowers the cost of
heating and cooling, however the less drafty a structure is, the harder
it is for a chimney to pull air from it. This condition is known as
"Negative Pressure" essentially when a home is under negative pressure,
the unit will burn only when the door is cracked open as there is no
resistance to draw, air can be pulled more easily through the doorway of
the unit straight up the flue. To correct this problem, attaching an
air intake from outside of the structure for the chimney to pull its air
through will take house pressure out of play as the air pressure would
be the same coming in the intake as it is going out the chimney.
Location in the home.
Air inside of a house behaves similarly to how it does in a chimney. Warm
air rises and cooler air descends. As this air is warmed and rises it becomes
trapped in the upper portions of the home. This actually causes the air
pressure inside the house to be higher close to the roof than it is in
the lower parts of the house, especially in the basement, which means
that the draw of the chimney has to work harder to pull air out of the
mild vacuum that is present in basements. this also means that the
higher in the house the stove is located in (upper floors) draw would be
stronger as the inside air pressure would be slightly higher than the outside pressure.
How New is House?
How is Stove Being Operated?
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