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How It Works!!
There are many reasons why someone would decide to
purchase a wood pellet burning appliance. It may be cost of operation,
efficiency, environmental concerns, safety or beauty. But, by far, the
most common reasons for buying a pellet stove are cleanliness and
convenience. Here are some hints and information that will help you to
understand your pellet stove and keep it operating cleanly and
efficiently. As always, remember to follow the safety guidelines
outlined in your owners manual.
About Your Stove
The fuel is stored in a bin at the rear of the
pellet stove and is usually referred to as the "hopper". At the
bottom of this bin is an opening that allows the fuel to enter into the
fuel feed system.
The fuel feed system moves the pellets from the storage hopper
to the combustion chamber. The most common style of fuel feed is a screw
auger driven by a slow moving high torque motor.
Although these feed systems are extremely reliable, an occasional
jam is possible. If you should experience a jam please refer to your
owner's manual or contact your dealer for instructions. Shorter pellets
allow for more fuel to fit into the auger opening offering a consistent
feed which is very desirable for operation on low burns as well as reducing
stress and wear on the fuel feed components.
If you use a pellet that is shorter than what was previously
used, an increase in the air rate may be required to compensate for the
additional fuel that will be dispensed by the auger.
Very long pellets have a tendency to bind together to form a log jam
or bridge over the feed opening interrupting the fuel feed. It is very
important to keep the fuel feed opening free of fines as they can obstruct
movement of the fuel into the feed system. It is recommended that you
vacuum or allow the hopper to run completely empty once every ton or fuel.
The fuel has now successfully been transported from the hopper to
the combustion chamber. This area is sometimes referred to as the
"firebox" where the burning of the fuel actually takes place.
Contained in the combustion chamber is the burnpot and the heat exchanger.
The Burn Pot
The burnpot accepts delivery of the incoming fuel
and mixes it with forced air to produce a hot, clean burning fire. There
are obviously several different styles of burnpots and different ways of
adding air to the burnpot for proper operation of your stove. This area
must be kept clean for the best mix of air and fuel.
Air To Fuel Ratio
The burnpot acts as the carburetor for the stove,
mixing the air and the fuel. Just like a car, the adjustment of the air
and fuel rates on a pellet stove is crucial to optimum performance.
Under normal operation the flame in your stove should appear to be bright
yellow or white. You may experience a white or gray build up of ash on the
glass on high burn and a darker fluffy ash on low burn.
If you notice
a lazy orange sooty flame or build up of a brown sticky caramel like substance,
these are signs of an improper inefficient burn.
Some stoves are
equipped with air dampers or adjustable feed openings that you may personally
be able to adjust. Other stoves will require adjustment to the control board
which may require a qualified technician.
Clinkers
You may also experience in the firebox what is
referred to as "clinkers". A clinker is a hard ash formation
that is occasionally created when the ash that is present in the burnpot
actually begins to melt. Many of today's highly efficient pellet stoves
operate near the combustion temperatures that are required to melt ash. Once
the ash begins to melt it may obstruct the air holes of the incoming air and
affect the proper mix of air and fuel.
Incorrect adjustment of the air
to fuel ratio can greatly increase the likelyhood of clinker formation.
This is due to the stoves inability to adequately burn the excess fuel
and remove the excess ash that is building up in the burnpot.
Clinkers
are very easily removed by use of the ash tool or rake that is supplied with
your pellet stove. This can quite often be performed while the stove is in
operation. Care must be taken not to remove all of the hot coals or the stove
will go out and, as always, you should be careful of the hot surfaces of the stove.
The Heat Exchanger
Also located in the combustion chamber is the
heat exchanger which is designed to transfer the heat being produced by the
burning fuel in the burnpot into clean hot air for distribution into the
home. This is usually done by a chamber or a series of tubes located in the
firebox that the hot air and gases pass over, heating the outside of the
chamber before exiting the stove. Fresh air is passed through the inside of
the chamber drawing the heat out of the stove and into the room.
For maximum
efficiency the surface of the heat exchanger should be cleaned regularly. The
frequency of these cleanings will depend on your stove design and may range
from daily to monthly. Please refer to your owner's manual for cleaning instructions.
Exhaust Venting
At this point your pellet burning appliance has
performed the function that it was designed for and all that is left are
the by-products of combustion, which are exhaust gases and ash.
The two main
styles of exhaust venting are natural draft and power. Both remove the
harmful gases from inside your stove to safely outside the home.
Natural draft venting uses the hot air and gases inside the
stove to naturally rise
and exit out through the vent pipe in
much the same manner as a traditional woodstove.
Power venting uses a mechanical fan to either push or pull the
gases out of your stove. This style of
venting is very similar in operation to the venting used on a clothes
dryer.
Always be sure to strictly adhere to
the manufacturer's exhaust installation guidelines. Incorrect installation
of the exhaust system will result in operational and performance problems.
Vent Maintenance
Also carried out through the vent pipe are small
amounts of very fine ash. This ash can eventually build up and block the
vent if not properly cared for. Many stoves have ash bins or traps to
capture the ash in the firebox or vent outlet prior to reaching the vent
that require occasional cleaning.
In the event that your vent pipe should
become blocked a small amount of smoke may leak into your home. Most pellet
burning appliances are equipped with a safety switch that will interrupt
its operation and minimize any possible exposure.
A regular inspection and
cleaning schedule should be maintained to ensure proper operation. While
inspecting the vent system, particular attention should be paid to the
assembly joints for possible leaks. Leaky joints may cause poor performance
as well as result in exhaust gases and ash leaking into the home. Many
stove manufacturers recommend the use of high temperature silicon sealant
on the exhaust vent joints to prevent leaks.
Additionally, it is suggested that you only use a vacuum that is
specifically designed for cleaning wood and pellet stoves. A standard household
vacuum cleaner does not have the proper filter that is needed to trap the
very fine ash produced by a pellet stove and will force that fine ash into
your home creating a thin film of dust on your furniture.
It is always
recommended that a non-combustible pail with lid be used to remove ashes
from your home and that ashes always be disposed of safely.
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Solutions To Common Problems
If you should experience a dirty or sooty burn in
the combustion chamber some possible corrective measures are:
- Review proper adjustment of any air dampers if
your stove is so equipped.
- Remove any excess ash, carbon or clinkers from
the burnpot.
- Clean any air inlets to the appliance.
- Remove (if possible) the burnpot and clean the air
openings in the burngrate.
- Inspect the burnpot and burngrate for proper fit and
possible air leaks. Note: Many stoves are equipped with gaskets
in this area that should also
be inspected.
- Inspect door and window seals for leaks.
- Clean firebox and vent ash traps.
- If possible, re-adjust your air and fuel feed
rates for a leaner burn. This is an adjustment that may need to be
performed by an authorized stove technician.
The first thing you should do when you encounter a
problem with your pellet
burning appliance is to review the instructional video and/or manuals supplied
with your stove. If you can not resolve the problem, then contact your
retailer for additional instructions.
Maintenance Checklist
To ensure optimum performance from your pellet stove
perform the following maintenance procedures regularly. (Your stove may or
may not be equipped with the items listed below.)
- Adhere to the cleaning and maintenance schedule
as outlined in your owner's manual.
- Store your fuel in a clean dry place.
- Occasionally clean your hopper of pellets and fines.
- Regularly clean and inspect your vent system.
- Clean and lubricate fans as suggested.
- Never use your household vacuum to clean the firebox
of your stove.
- Inspect and clean the firebox and vent system
ash traps as suggested.
- Keep air filters clean.
- Clean your heat exchanger as recommended.
- Inspect and clean the burnpot if necessary.
- Inspect and adjust door seals.
As you can see the operation of your pellet burning appliance may not be
as complicated as you may have thought. There are many things that you, as a
consumer, can personally do to ensure its proper operation. You may wish to review
your owners manual or video at this time to acquaint yourself with the
appropriate operation, cleaning and maintenance schedule for your particular stove.
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Last updated : 22 May 2009.
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