David
E. Baker
University of Missouri Extension
After
selecting and installing a wood stove you will be anxious
to get it going. Learn to operate and maintain the stove so
it can provide warmth and comfort in a safe and efficient
manner.
This
guide provides general information on the operation and maintenance
of wood stoves as supplemental heat sources in residences.
Once
a good stove has been selected and installed correctly, the
next important factor is proper operation. Many problems that
arise with a correctly installed stove are the direct result
of incomplete combustion.
Combustion
Combustion consists of a complex chemical reaction between the fuel (wood) and oxygen. The combustion of wood in a stove results in heat and water vapors, carbon dioxide and other products of combustion such as gases and ash. To ensure satisfactory combustion and safe operation, you must meet several conditions:
- Keep
a continuous supply of oxygen for the fire and the occupants
of the room or area.
- Use
a proper amount of fuel (wood) not enough to cause overheating,
but enough to maintain a flue temperature that prevents
the accumulation of creosote residues.
- Burn
properly to avoid wasted fuel and toxic products of combustion
such as carbon dioxide.
- Remove
unwanted products of combustion. Gaseous products should
be continuously removed while the stove is in operation,
and solid products such as ashes should be disposed of safely.
Ensure complete combustion by supplying air and maintaining a sufficient heat level. Incomplete combustion results from an insufficient air supply, misapplied air or insufficient heat.
Wood
combustion
There are three basic stages to wood combustion:
- Water
is removed by evaporation and vaporization. This heat does
not warm the stove or room.
- At
500 degrees F, the wood starts to break down chemically,
and volatile gases are formed. These vapors contain from
50 to 60 percent of the heat value of wood. At approximately
1,100 degrees F, these gases, when mixed with the proper
amount of air, break into flames and burn. To ensure complete
combustion, maintain this temperature and a sufficient air
supply.
- After
the release of gases, the remaining material (charcoal)
burns at a temperature in excess of 1,100 degrees F. When
charcoal is completely burned, a small amount of ash remains.
Since
moisture must be evaporated and expelled before wood will
burn, the wood should be cut and seasoned. Use well-seasoned
wood with a low moisture content to reduce the likelihood
of creosote buildup.
When
building a fire, follow the manufacturer's recommendations.
The following steps will also serve as a guide:
- Open
the damper completely.
- Place
paper and/or kindling over the entire bottom of the fire
box to achieve an evenly burning fire. Never use flammable
liquids such as gasoline, lighting fluid or kerosene to
start a fire an explosion may result.
- To
achieve a better chimney draft, hold a lighted roll of paper
near the flue opening inside the stove to warm the flue
and start it drafting.
- Light
the wood and paper in the grate. When the kindling is burning,
add additional seasoned wood to build up a hotter fire.
Be careful at first when adding wood to avoid smothering
the fire.
- With
the fire door closed, use the draft regulator to maintain
the desired heat. The proper heat can only be obtained by
trial and error because conditions of the fuel (moisture
content, hard or soft wood), space being heated, individual
preference, outside temperature and wind vary. After some
experience with your stove, you should learn the best setting
for your needs.
New stoves
with cast-iron parts should be "seasoned" to avoid cracking.
Do this by building only small fires for the first two or three
times.
The
entire system must be properly maintained to operate safely
and efficiently. The chimney connectors, joints and flues
must be clean and in proper working order.
When
wood is burning rather slowly, the smoke usually contains
a substance called creosote that collects in the relatively
cool chimney flue. The main causes of creosote buildup are:
- wet
or unseasoned wood
- incomplete
combustion or
- cool
surfaces
The best
way to control creosote is to prevent its buildup by maintaining
a briskly burning fire with dry, well-seasoned wood. Maintain
a flue temperature exceeding 250 degrees F to prevent creosote
condensation.
Some
new, more efficient stoves deliver more heat to the room than
an open stove or fireplace. This reduces the amount of heat
escaping up the chimney and lowers the flue temperature. Make
sure creosote is not building up as a result of improper operation
of these stoves. Additional inspections and clean-outs may
be needed.
With
the increased accumulation of creosote in the flue comes the
increased possibility of a chimney fire. The combustion of
these creosote deposits is most likely to occur during a very
hot fire in your stove. Burning creosote deposits cause a
very intense fire, a roaring noise, and flames and sparks
shooting from the top of the chimney.
Any
chimney, metal or masonry, can be weakened or deformed by
a chimney fire. The complete chimney should be inspected after
a fire, and any repair should be made or parts replaced before
re-starting the stove.
If a
fire occurs, follow these steps to reduce your losses:
- Call
your local fire department immediately.
- Close
all openings and draft controls on the stove.
- If
the fire is burning vigorously, squirt a multi-purpose dry
chemical extinguisher or throw baking soda onto the fire
in the stove. The chemicals will travel up the chimney and
may extinguish the fire. If possible, avoid introducing
water into the chimney; the water could damage a relatively
brittle heated flue liner.
Stovepipes
and chimney flues should be inspected each year before you
use your stove. Look for cracked flue liners, broken or missing
bricks, heavy creosote deposits, bird nests and other foreign
material. Thoroughly clean the flue and stovepipe of any soot
and other residues. Repair the chimney or replace the stovepipe
to avoid any problem later in the season.
The
stovepipe and chimney should be inspected frequently during
the heating season for creosote buildup. If you use an air-tight
stove, check the stovepipe at least once a month.
Your
chimney cleaning schedule will depend on how frequently your
stove is used and how it is operated. Should your chimney
have an excessive buildup, a stiff wire chimney cleaning brush
like the ones used by professional chimney sweeps are available
at a reasonable cost.
Some
people recommend pulling a bag containing wire netting weighted
with chains or rock up and down the chimney; others use tire
chains or wire netting without a bag. The effectiveness of
these techniques is questionable. Tire chains or a weighted
bag may damage the flue liner.
Store
ashes in a non-combustible metal container with a tight lid.
The closed container should be placed on a non-combustible
floor or on the ground well away from all combustible materials
pending final disposal.
In addition
to the extinguishers already in the home, a multipurpose fire
extinguisher should be installed for each stove. The extinguisher
should be located near the stove within easy reach. To offer
your family additional protection in case of fire, equip your
home with an early warning fire detection system.
- Because
of high temperatures when the stove is operating, locate
the heater out of traffic and away from furniture and draperies.
- Tell
children about the high surface temperatures and keep them
away from the stove so they avoid getting burned or igniting
their clothes.
- Carefully
supervise young children when they are in the same room
with the heater.
- Do
not place clothing or other flammable material on or near
the heater.
- Have
a qualified person install and service the stove and inspect
it before use and at least annually.
- Keep
combustible materials away from heaters to avoid the possibility
of igniting such materials. These include combustible walls,
ceilings, furniture, rugs, draperies and fuels.
Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002 This
document is
GO1731
,
published by the University Extension, University of Missouri-Columbia,
Columbia, MO 65211. Publication date: March 1991.
David
E. Baker, University Extension, Department of Agricultural
Engineering, University of Missouri and Lincoln University,
Columbia, Missouri 65211.
Issued in furtherance of Cooperative Extension Work Acts
of May 8 and June 30, 1914, in cooperation with the United
States Department of Agriculture. Ronald
J. Turner, Interim Director, Cooperative Extension Service,
University of Missouri and Lincoln University, Columbia,
Missouri 65211. An equal opportunity institution.
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