Vermont Casting 1610CE 사용자 설명서

19

A stove is part of a system, which includes the chimney, 
the operator, the fuel, and the home. The other parts of 
the system will affect how well the stove works. When 
there is a good match between all the parts, the system 
works well. 
Wood stove or insert operation depends on natural 
(unforced) draft. Natural draft occurs when the exhaust 
is hotter (and therefore lighter) than the outdoor air at 
the top of the chimney. The bigger the temperature 
difference, the stronger the draft. As the hot gases rise 
through the chimney they provide suction or ‘draw’ that 
pulls air into the stove for combustion. A slow, lazy fire 
with the stove’s air inlets fully open indicates a weak 
draft. A brisk fire, supported only by air entering the 
stove through the normal inlets, indicates a good draft. 
The stove’s air inlets are passive; they regulate how 
much air can  enter the stove, but they don’t move air 
into it. 
Depending on the features of your installation - steel or 
masonry chimney, inside or outside the house, matched 
to the stove’s outlet or oversized - your system may 
warm up quickly, or it may take a while to warm up and 
operate well. With an ‘airtight’ stove, one which restricts 
the amount of air getting into the firebox, the chimney 
must keep the stove’s exhaust warm all the way to the 
outdoors in order for the stove to work well. Some chim-
neys do this better than others. Here’s a list of features 
and their effects.

Masonry is a traditional material for chimneys, but it can 
perform poorly when it serves an ‘airtight’ stove. Mason-
ry is a very effective ‘heat sink’ - it absorbs a lot of heat. 
It can cool the chimney gases enough to diminish draft. 
The bigger the chimney, the longer it  takes to warm up. 
It’s often very difficult to warm up an outdoor masonry 
chimney, especially an oversized one, and keep it warm 
enough to maintain an adequate draft. 

Most factory-made steel chimneys have a layer of 
insulation around the inner flue. This insulation keeps 
the chimney warm. The insulation is less dense than 
masonry, so a steel  chimney warms up more quickly 
than a masonry chimney. Steel doesn’t have the good 
looks of masonry, but it performs much better. 

Because the chimney must keep the smoke warm, it’s 
best to locate it inside the house. This uses the house 
as insulation for the flue and allows some heat release 

into the home. An indoor chimney won’t lose its heat 
to the outdoors, so it takes less heat from the stove to 
heat it up and keep it warm.

The common wisdom tells us that a taller flue draws 
better than a short one. This isn’t necessarily so. If a 
chimney is tall enough to meet the safety requirements 
of the 2/3/10 foot rule, then adding more height isn’t the 
right answer to a draft problem. In fact it could make the 
problem worse by adding more mass to the chimney 
system, which must be warmed up, a distance from the 
heat source (the stove). Don’t make a chimney taller 
unless you must in order to meet the safety rules, or un-
less there’s some nearby feature causing a downdraft. 
Even then, there are downdraft-preventing chimney 
caps available, which are probably the smarter choice. 

The inside size of a chimney for an ‘airtight’ stove 
should match the size of the stove’s flue outlet. When 
a chimney serves an airtight stove, more is not better; 
in fact, it can be a disadvantage. Hot gases lose heat 
faster as they travel slower through a chimney; if we 
vent a stove with a 152mm (6”) flue collar [181 sq cm 
(28 sq in area) into a 254 x 254 mm (10 x 10”) flue, the 
gases slow to one third their original speed. This allows 
the gases to cool more rapids, which weakens draft 
strength. If an oversized flue is also outside the house, 
the heat it absorbs gets transferred to the outdoor air 
and the flue usually stays cool. 
It is common for a masonry flue, especially one serving 
a fireplace, to be oversized for the stove. It can take 
quite a while to warm up such a flue, and the results 
can be disappointing. The best solution to an oversized 
flue is an insulated steel chimney liner, the same diam-
eter as the stove or insert’s flue outlet; the liner keeps 
the exhaust warm, and the result is a stronger draft. An 
uninsulated liner is a second choice - the liner keeps 
the exhaust restricted to its original size, but the hot 
gases still must warm up the air around the liner. This 
makes the warm-up process take longer.

Every turn the exhaust must take as it travels to the 
chimney top will slow it down. The ideal pipe and chim-
ney layout is to vent vertically into a completely straight 
and vertical chimney. If you are starting from scratch, 
use this layout if possible. If the stovepipe must elbow 
to enter a chimney, locate the thimble about midway 
between the stove top and the ceiling. This achieves 
several goals: it allows the gases to speed up before