JUCA Materials, Construction
Since NORMAL woodstoves are meant to be operated near red hot for
maximum radiated heat, they should be constructed of cast-iron or
extremely thick steel in order to have a decent lifetime.
If the walls of a steel stove are allowed to get red-hot and then
cooled down, microscopic flakes of metal 'pop off' the surface.
This is called "spalling." After this happens few hundred
times, enough metal has left to produce a hole in 18 gauge steel.
This is a relatively common problem in 'Heatilator-type' built-in
fireplaces that often use 18 gauge steel. (This is also why the
old "barrel-stoves" would burn out in a couple months).
If thin steel units are operated so that they do NOT often get
red-hot, they can last almost indefinitely. This is part of the
premise of the JUCA products. We arrange so that most of the metal
surfaces that are exposed to the fire are forced-air cooled from the
other side. Conventional fires just can not heat the metal fast
enough to get it red-hot under these conditions. This effect will
allow long useful lifetimes for our products as long as they are
Generally, the hottest areas of steel in a JUCA operate at about 450°F.
Most woodstoves are intended to RADIATE most of their heat, and 450°F
is just no where near hot enough to create huge radiant heat. It turns
out that the amount of radiant energy given off goes up as the FOURTH
POWER of the temperature! When potbelly or Franklin or modern cast
iron woodstoves operate at a dull red hot (750°F), they radiate
huge amounts of energy to the immediate area. Since JUCAs are designed
NOT to be radiant heaters (they primarily use heat exchangers to
capture the heat in warmed air) they can stay at the designed 450°F
for an extremely long lifetime.
A second reason we are confident in our products' durability is
that we use the heaviest materials we can while still allowing the
units to be moved. (most of our units weigh 400-600 pounds.) We
feel that the heat exchanger tubes are subject to the greatest
punishment since they are in the direct path of the flame--tips
which is the hottest part of a fire. Therefore, we use 10 gauge
(1/8") tubing. We use 10 and 11 gauge for the rest of the firebox
of the unit, much thicker than the common 18 gauge used by some other
fireplace companies. Our doors are made of 3/16" thick material.
A further reason for an extended lifetime is the size of fire
commonly necessary for house heating. The fact that our units are
so efficient and capable of distributing the heat evenly in the
house allows most owners to use a much smaller fire than one would
normally expect. The smaller fire is less likely to affect the
structure of the unit. The very large firebox also keeps most of
the steel surfaces far enough away from the actual flame tips.
As to the construction safeguards we employ, we use unique
assembly techniques that minimize the chance of any future problems.
The heat exchanger tubes pass through precision holes in the body and
are securely fillet welded ON THE OUTSIDE so there is no possibility
of a tube pulling out. Of course, the units are inspected several times.
There is another built-in safeguard in the JUCA units. If someday
a flaw would ever develop and result in a hole in the firebox
chamber, smoke would still not get into the warm air system. The
unit is designed to have a very slight vacuum (i.e. lower than
atmospheric pressure) in the firebox. The warm air chambers have a
slight pressure (i.e. higher than atmospheric pressure) when the
blower is operating. Even if a flaw developed, the net effect
would generally just be to lose a little warm house air up the chimney.
You can see that our units are safety-oriented. Sturdy
materials, quality construction and a design that doesn't require
a roaring fire; all contribute to a product that will serve you
long and well.
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