We at JUCA have always thought that was foolish. Why not have a much
bigger firebox (nearly 5 times as big) and then all the numbers above
are 5 times as big, too! There is around 600,000 Btu of heat in the
wood for heating the home. By using it at 60,000 Btu/hr, there is a
nice constant 10 hours of heat, to heat the WHOLE house, for an ENTIRE
night. If you think about it, NO product with a 2 or 3 cubic firebox
could realistically do that!
Huge JUCA Firebox
JUCAs have always been known for their huge fireboxes. Where competing
wood-burners often have 2 or 3 cubic foot fireboxes, a JUCA B-3B
has a 9.5 cubic foot firebox! The built-in Model F-9A has a
12.3 cubic foot firebox! (The picture shows an
18 inch long ruler amd some 26" long, 8" diameter logs in
a JUCA B-3B.)
This huge firebox allows several benefits:
Of course, it allows you to burn much bigger pieces of wood, pretty
much anything you could carry! (An 8" diameter, 24" long
hardwood log weighs about 30 pounds.) So convenience is a result.
But there are more important results, as well.
It allows you to put enough wood IN it to be able to produce substantial
heat for many hours. Each pound of wood has available about 6,000
Btu of heat in it. A competing 2 cubic foot firebox, can realistically
contain about 30 pounds of small pieces of wood. In other words, about
180,000 Btu. If that competing product is 70% efficient, that means
about 125,000 Btu of heat for the home. That's it! No more! By setting
the draft control, it is possible to gain this heat as 50,000 Btu/hr
for 2.5 hours, OR as 12,000 Btu/hr for 10 hours. Either enough to heat
much of the house, if you are willing to load it every 2.5 hours, OR
enough to heat a single good sized room for a full night!
The large firebox allows having the heat exchanger areas substantially
above the fire. THIS IS REALLY IMPORTANT! If it was closer, as in
many competing products, the (relatively) cool metal surfaces of the
exchangers can "chill" the flames themselves and thereby affect the
completeness of the burning process. This effect is one of the
reasons why many competing products create a lot of creosote and pollution,
and why they therefore need catalytic combustors and/or secondary air
to try to solve these problems. Since JUCA design allows extremely
complete combustion IN THE FLAME TIPS, there is no need to try to
"re-process" the smoke later.
Another result of the JUCA's large firebox is that THICK logs can
be burned. It turns out that wood (or anything else) can only
burn (or oxidize) at its surface, where it can interact with the
oxygen in the air. As that surface wood burns and disappears (or
falls away), new wood is exposed which can then burn.
Thick pieces of wood therefore burn gradually (and evenly) for
a long time. With this fact in mind, a combustion system can be
designed (as in the JUCAs) where plenty of oxygen is available
around the fire area. As each particle of wood burns, there is
plenty of oxygen present to ensure extremely complete combustion.
Therefore, VERY high combustion efficiency exists and very little
pollution or creosote is created in the smoke. At the same time,
the thickness of the wood pieces causes a rather constant AREA of
wood pieces to be on fire, therefore making heat PRODUCTION (and output)
very constant for a very long time. All the desired characteristics
of a perfect wood-burner!
Most competing products have smallish fireboxes. This then requires
small, split pieces of wood to be burned. These sized pieces of wood
would burn up very quickly in the presence of a lot of air, as they
did in the old Potbelly stoves and Franklin stoves. Those (non-air-tight)
units burned reasonably cleanly, but created heat for only an hour or so,
and too much during that hour! Therefore, nearly all manufacturers
(except us!) stayed with the tiny firebox, and turned
to limiting the amount of air available to the fire, the so-called
Air-Tight design concept. They DID accomplish their goal of longer
burn time and more even heat production, but at the cost of rather incomplete
burning due to insufficient oxygen present for all the chemical reactions
which need to occur in complete combustion. Therefore, they are forced
to try to complete these reactions later, either in a catalytic combustor
or by adding heated secondary combustion air later. Life is very
complicated for designers of such devices, only because the basic
premise of Air-Tight operation has such a major flaw.
(Interestingly enough, as those products developed a VERY bad reputation
for creating a lot of creosote and pollution, one of the approaches
that became popular was to convince customers to buy the very smallest
air-tight product that might do the job, so that it would generally
operate "wide open" and avoid air-tight operation!)
JUCAs NON-Air-Tight design allows such complete combustion
in the original flame tips, that our NORMAL operation is better than
that when Air-Tight products are operated at their optimum.
For more technical info, Click here
The JUCA Home Page is at:
E-mail to: JUCA1@mb-soft.com