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Econoburn Technical FAQ
Revised 2-11-10
1)
Where can I install my
new Econoburn Gasification wood boiler?
Wherever it is most convenient… the Econoburn boiler is
much more versatile than traditional wood stoves or wood boilers.
Indoor Model:
Installation of the indoor Econoburn is not limited to just the basement.
The Indoor boiler also installs easily in a garage or outbuilding, all the
while using far less wood than a traditional outdoor wood boiler.
Outdoor Model:
The outdoor Econoburn boiler is designed for installation on any stable
surface (i.e. concrete). Its specially designed air intake system
pre-warms the combustion air to ensure complete gasification.
2) Which installation is less
expensive… indoor or outdoor?
If you have a suitable chimney inside your home, an indoor
installation will likely be less expensive than an outdoor installation.
An outdoor installation requires insulated underground pex tubing, a
concrete pad, and a trench for the piping (though no plate heat exchanger
is required). On the other hand, if you do not have a suitable chimney
inside the home, the cost of relining an existing chimney or building a
new chimney from scratch may outweigh the costs of an outdoor
installation. Of course, replacing an existing outdoor wood
furnace with a new Econoburn Outdoor boiler is the LEAST expensive type of
installation!
3) Which installation is more
efficient… indoor or outdoor?
Both an indoor and outdoor Econoburn boiler will be far
more efficient than the typical outdoor wood furnace. However, if glycol
(antifreeze) is used, it will reduce the heat transfer rate of water by
around 7% to 10%. Another factor to consider is the heat loss of any part
of the boiler or piping that is exposed to unconditioned (outside) air.
4) How
can I justify the extra cost of a gasification wood boiler over a
conventional outdoor wood boiler?
Econoburn boilers are the best-built, most-efficient wood
fired boilers anywhere! Though Econoburn boilers may cost slightly more
than conventional outdoor wood boilers, their superior efficiency quickly
makes up the difference with reduced wood consumption. Also, unlike
open-system wood furnaces, there is no need to install a plate heat
exchanger (saving hundreds of dollars). Plus, because the Econoburn
boiler operates as a pressurized vessel, it often has a life expectancy
that is 2-1/2 times longer than conventional wood furnaces. Lastly,
further reducing the cost difference, Econoburn boilers are eligible for a
$1,500 Federal tax credit!
5) How long are the burn times on
an Econoburn wood boiler?
Though burn times vary by application (and by wood species
and moisture content), you can expect burn times ranging from 6-8 hours on
a cold day for a properly-sized system. What’s more, if you install
thermal storage, you may only need to fire the boiler once per day for (5
-10 hours at a time) to charge the tank.
6) Do I
have to burn dry seasoned wood in my new Econoburn wood boiler?
This is a question that we hear often. The bottom line
about firewood quality is this: No matter what stove, boiler, insert, or
other wood burning device you are using... the dryer the wood is, the more
heat you will get out of it, and the less of it you will burn.
Good, quality fuel is critical to achieve maximum output
from the Econoburn boiler. Seasoned hardwood (between 15 -22% average
moisture content) will yield the most output. Water in the wood does not
burn… it boils. And in order to get water hot enough to boil, it consumes
a substantial amount of heat from the wood – heat that is not available to
the system. Indeed, extremely high moisture content can even prevent the
wood from burning at all. Wood with 15% moisture content is about as dry
as wood gets by air drying, and 22% moisture content can be achieved in as
little as 6 weeks of summertime air drying, depending on species. While
it is possible to burn wood with a moisture content of up to 35 or 40%
(completely green depending on species and season), we don't recommend it
as the efficiency and output fall dramatically. For reference, wood that
is rotten or punky (decaying) will also reduce output and shorten burn
times. Punky wood holds vastly lower BTU’s per unit of volume compared to
high quality seasoned firewood, and can also hold more moisture than even
fresh-cut green wood.
7) Is it OK to over-size an
Econoburn?
Prior to selecting boiler size, a heat loss calculation for
the system is critical. Under-sizing a boiler can result in a system
unable to maintain an indoor temperature of 70 degrees; plus, a too-small
boiler will shorten burn times. On the other hand, over-sizing a
boiler slightly is acceptable and will lengthen burn times on systems
without thermal storage. Please note, however, at some point
during the heating season, any boiler without thermal storage will be
oversized for its application. An over-sized boiler will likely spend
more time idling and less time gasifying. Excessive idling will reduce
the efficiency and cause creosote to build up in the combustion chamber
and heat exchanger. To maximize efficiency and reduce creosote, only fill
the firebox enough to maintain a fire until the next refueling time is
feasible. This will force the boiler into gasification more often by
reducing the portion of the heat load satisfied by the upper chamber
alone.
8) How
efficient is an Econoburn gasification wood boiler in comparison to other
boilers?
The Econoburn boiler achieves an amazing 87% thermal
efficiency! Conventional style wood furnaces (OWB’s) consisting of
nothing more than a firebox and a chimney, produce efficiencies of just
25- 30%. OWB’s allow vast amounts of smoke and gas to escape out of the
chimney unburned. The Econoburn reclaims what would normally be lost up
the chimney as wasted energy and pollution, saving you time and money.
9) Does
it matter what species of wood I burn in my Econoburn wood boiler?
Yes, though any type of wood (including pine) can be burned
in an Econoburn, choice of species will greatly influence burn times. For
example, pine will burn much more quickly than hard maple. Below is an
estimate for the energy content of common wood species – the more energy
(BTU’s), the longer the burn time. Figures are based on 20% moisture
content.
|
Species |
Million BTU's per cord(4’x4’x8’) |
Weight
per cord (lbs) |
|
Shagbark Hickory |
28.0 |
4,330 |
|
Eastern Hornbeam |
27.5 |
4,250 |
|
Ironwood |
27.1 |
4,015 |
|
Black
Birch |
26.8 |
3,895 |
|
Black
Locust |
26.7 |
3,830 |
|
Bitternut Hickory |
26.7 |
3,830 |
|
Apple |
26.5 |
4,115 |
|
White
Oak |
25.8 |
4,020 |
|
Sugar
Maple |
24.2 |
3,800 |
|
Red
Oak |
24.0 |
3,685 |
|
White
Ash |
23.6 |
3,690 |
|
Yellow
Birch |
23.5 |
3,655 |
|
Red
Elm |
21.6 |
3,110 |
|
Paper
Birch |
20.3 |
3,180 |
|
White
Birch |
20.3 |
3,180 |
|
Black
Walnut |
20.2 |
3,192 |
|
Cherry |
20.0 |
3,120 |
|
Green
Ash |
19.9 |
2,880 |
|
American Elm |
19.6 |
3,150 |
|
Black
Ash |
19.2 |
3,065 |
|
Red
Maple |
18.8 |
3,035 |
|
Hemlock |
15.9 |
2,480 |
|
Quaking Aspen |
14.5 |
2,290 |
|
White
Pine |
14.3 |
2,240 |
10) What is thermal storage and
how is it used?
Thermal storage is heat energy in the form of hot water.
The objective is to fire the boiler at full throttle for a few hours, and
store – in 500-1,000 gallon water tanks – all excess heat not needed by
the heating system. Afterwards, your system draws heat from the storage
tanks to provide heat for your home. Burning wood this way ensures that
the combustion is as efficient as possible by keeping your boiler in its
gasification mode for the entire run time. Plus, it provides more
flexibility with regard to when you have to fire your boiler. For
example, in the shoulder seasons (early fall and late spring), you may
only have to fire the boiler once every few days in order to charge the
thermal storage tanks.
11) Some
gasifiers need thermal storage to operate... does the Econoburn?
No. Econoburn was designed to be flexible. With proper
operation and maintenance, there is no need for thermal storage beyond the
water that the boiler itself holds. That said, thermal storage does
present some advantages – see #10 above.
12) How
much maintenance is there on an Econoburn wood boiler?
Clean boilers are more efficient than dirty ones.
Fortunately, the Econoburn runs very cleanly and is designed to operate
with minimal maintenance. Just follow these steps:
A)
Econoburn’s turbulators and heat exchange tubes will need
to be cleaned once per season.
B)
The bottom chamber should be cleaned twice per week during
steady use. (Ash in the lower chamber can reduce thermal transfer
through the lower refractory mass.)
C)
The upper chamber should be kept clean by letting the
boiler burn down to coals several times per week and raking the ash though
the nozzle into the bottom chamber for removal.
D)
Excess ash and loose soot should be removed as soon as the
boiler is shut down for the season.
13) The
Econoburn wood boilers are made from carbon steel... won't they rust?
No! Unlike traditional outdoor wood furnaces, the
Econoburn boiler is a closed loop system (the water inside the boiler is
not open to the outside air). With no oxygen in the system, no rust can
occur! Note: do not use pex tubing that does not have an oxygen
barrier.
14) Why
purchase a carbon steel Econoburn wood boiler over a stainless steel wood
boiler?
Carbon steel is the best
material for building a wood boiler. Carbon steel has about half the
thermal expansion rate of 300 series stainless steel. While carbon steel
is stable under extreme temperatures, stainless steel has a tendency to
"stretch," causing what is known as
Stress Corrosion Cracking.
Secondly, Carbon steel has a much higher thermal conductivity rating than
stainless steel. This means that the heat produced in your boiler gets
into the water faster, resulting in less heat loss through your chimney.
A more efficient, longer lasting boiler means less wood, less work, and
less expense!
15)
Does the Econoburn boiler produce any smoke?
There are a couple times during a burn cycle that an
Econoburn will produce a small amount of smoke. After lighting a new
fire, it will take a few minutes to establish a coal bed large enough to
raise the temperature of the refractory to a point where the wood gas will
combust. This generally takes between 10 and 30 minutes during which time
your boiler will produce a little smoke. Once a coal bed is established,
the smoke is burned before it is allowed to exit the stack, sending a
clean, colorless, and nearly odorless gas up your chimney. Another time
your boiler will produce a little smoke is immediately after the boiler
comes out of an idle state. During idle, the coal bed and refractory cool
down somewhat. It generally takes a minute or two for the blower to fan
the coals and generate the heat required to again begin combustion of the
wood gas.
16) Is the Econoburn certified for
indoor use?
Yes, Econoburn’s indoor model is safe to install indoors.
Indeed, it can be installed with as little as 0” clearance to combustibles
on each side and 18” clearance to combustibles in the back. In addition,
the
Econoburn boiler carries the ETL - WHI listing. WHI is the
safety standard mark used by the solid fuel industry and is the legal
equivalent of UL. WHI tests not only to UL standards, but also CSA
(Canadian) standards, which are far more difficult to achieve.
17) Is Econoburn’s efficiency
rating certified?
Yes, two independent labs have certified the efficiency of
the boiler. |