© 2021 United States Stove Company
19
A GUIDE TO BURNING COAL
Furnaces that are capable of burning coal usually will
burn both Bituminous and Anthracite coal. Anthracite is
perhaps the best coal fuel because of its long even burn
time, high heat output, and cleanliness which make it a
good choice for the home. However, keep in mind it is a
much more difficult fuel to use, requires more care and
patience, is not so widely available, and is usually much
more expensive than Bituminous.
SIZE OF COAL
Most sizes of Bituminous Coal will work in a coal furnace;
for best results we recommend large “nut” coal to small
“egg” coal (1-3/4” diameter to 4” diameter). When
burning Anthracite, use “egg” or “broken” with sizes
between 2-5/16” thru 4-3/8”. Note that it is important
to the long life of your stove to buy coal which has been
sized and cleaned. Cleaning ensures removal of rocks and
other minerals. Never use coal smaller than 1” or larger
than 5” in diameter. Small sized coal will smother the fire.
Too large a size of coal will not burn well.
STOVE OPERATION
All coal fires should be started with wood which will
allow the fire to get hot enough to ignite the coal. The
best ignition fires utilize dry pine or other resinous soft
woods as kindling, with hard wood (oak, hickory, ash)
added to increase the heat prior to addition of the coal.
Before starting the fire, open the stove pipe damper (if
equipped), turn the thermostat to high, open the ash
pit door and feed door, place newspaper and finely split
kindling on the grate, light the paper, add larger hard
wood after the kindling is burning brightly. Caution: Never
use gasoline, lantern fuel, kerosene, charcoal lighter fluid,
or other flammable liquids to start or freshen up a fire in
any heater. Place the larger pieces of wood on the fire so
that they are slightly separated and form a level for the
addition of coal. It will take 10 to 20 minutes before this
wood is thoroughly ignited. Adding coal too soon will cut
the air supply and smother the fire.
BURNING BITUMINOUS
Once your kindling and wood fire has produced a bed of
well established coals, start adding coal in layers allowing
each to ignite before adding more. Bituminous has a high
volatile content and, as a result, should be fired with the
“conical method” - with the highest portion of your fire
bed in the center of the firebox. The first flames will be
long and generally orange or yellow and produce quite a
bit of smoke. As the gases burn off the flames become
shorter, change color and produce less smoke. Once
the fire is WELL ESTABLISHED add coal to the center
of the firebox forming the cone. Burning in this fashion
allows heat to drive off the volatile gases, and turbulence
created increases the burn efficiency. There will have to
be some experimenting with the individual setup as no
two chimney’s or installations are going to be the same.
Just remember to allow enough air to enter the firebox
and keep the stove pipe damper open so that volatile
substances are properly burned. Before refueling, take the
time to break up the cone a little with a poker, especially
if it has caked over or formed a crust. But, be careful not
to mix the coal as this increases the chances of forming
clinkers. When shaking the grate(s) be gentle. Just a
few short movements - a couple of “cranks” - is better
than a lot of agitation. The objective is to remove a small
amount of the ashes without disturbing the fire. Stop
when you see a glow in the ashes or the first red coals
fall into the ash pan. Excessive shaking wastes fuel and
can expose the grate(s) to very high temperatures which
can cause warpage or burnout. For overnight operation
(long duration burn time) shake the fire and add coal,
retaining the center cone. Once the volatile substances
are burned off, close the feed door and adjust the stove
pipe damper, if equipped. Then adjust the thermostat to
the desired heat level. More maintenance will be needed
with bituminous coal than with anthracite coal as more
soot will collect on heating surfaces and in pipes, requiring
more frequent cleaning.
ANTHRACITE
Add a thin layer of coal (preferably smaller chunks) to
the wood fire, being careful not to disturb it too much or
cut off the draft. Then, add a second heavier layer after
the coal is ignited and burning well. If necessary, add a
third layer to bring the coal up to the top of the front liner
(not above!). Be sure to close the ash door. Before adding
further fuel, be sure to leave a red spot of glowing coals
in the center of the firebox to ensure that the fire has not
been smothered and to help ignite the gases given off
by the new charge. A deep charge will give a more even
heat and a longer fire, but it may take one to two hours
before the whole bed is fully ignited. When the fire is well
established and the room is becoming warm, partially
close the dampers. Some experimenting will have to take
place with each particular setting of all dampers and
controls as the chimney provides the draft necessary to
not only exhaust the smoke, but to pull combustion air
into the heater as well - and no two chimney’s perform
the same. Under ideal draft conditions, one should be
able to turn the secondary air supply below the feed
door (some models) to a near closed position - but leave
the ash pit damper at least partially open to prevent
the fire from going out. Adjust the stove pipe damper to
reduce the draft on the fire. With anthracite there will be