« Back to Articles Index Page
Back to Hearth.com Home »


ARTICLES - Coal - So you’re considering a coal stove?

(written by Corie Podschelne)

Perhaps you’ve been a long time wood burner and are looking for a stove that requires less tending; or maybe you’re new to solid fuel room heating completely.  Burning coal, especially for a new coal user, can be particularly daunting due to difficulties in igniting a coal fire.  Also, coal burning has some unfortunate (and false) stigmas surrounding it that come from a different era of coal burning. Modern coal stoves are amazingly simple to operate, extremely efficient and clean burning and require significantly less tending than a similar wood burning unit.  This article will focus primarily on burning hard coal, also referred to as anthracite coal, however of the concepts will be just as useful when considering soft or bituminous coal.

-Coal Sizes

image

Anthracite coal comes in a variety of sizes; certain stoves require a specific size of coal whereas other stoves may be able to burn a few different coal sizes.  While there are more sizes of hard coal than those listed blow, these are the primary four sizes that will be used in most coal stoves.

Rice - 3/16” to 5/16”

Pea - 9/16” - 13/16”

Chestnut - 13/16” to 1 5/8”

Stove - 1 5/8” to 2 7/16”

-Stove Types

1) Stoker

A. Introduction

A stoker stove is an automatic coal burning unit, wherein some type of stoker mechanism feeds fresh coal to a burning fire at a feed rate set by the user.  Air is generally forced through the fire from the bottom by a blower or by a flue mounted draft inducer.  The coal stoker stove operates on much the same principle as the pellet stove.  The user must simply keep the hopper filled with coal and the ash pan empty and the coal stoker stove will run continuously. 
B. Venting

Stoker stoves, depending on manufacturer, can often be “power-vented” because of the forced draft within the unit, greatly simplifying the venting system and reducing cost.  In other words, many coal stokers can be direct vented much like a pellet stove, albeit with a different type of pipe.

C. Lighting Procedure

As of this writing, there are no self-lighting coal stoves on the market; therefore, the coal fire must be lit with a fire starting medium approved for the stove generally including gelled alcohol, fire-starter cubes and various other methods.  A full list of approved fire-starters will be including in the owner’s manual which accompanies the stove.  The downside of these stoves is that they do require electricity and this can be problematic in areas with frequent power outages.  However, the ease of which these stoves can be operated and the low user involvement make them very useful for users who as frequently away from the home for extending periods.

D. Things to look for

Grate/Burning Surface -A good stoker stove will have a heavy duty, cast iron or steel wear plate that can be replaced periodically; this is because the intense heat of the coal fire will distort this part over time. 

Ash Pan – Look for stoves that have large, sturdy ash pans coupled with a handle or other means for carrying the pan.  The deeper the ash pan, the longer the stove can operate without being cleaned out.

Blowers and Gear motors – Look for stoves that use high quality brand components in their stoves.  Good quality blowers are generally made by Fasco and various others; quality gear motors are made by Merkl-Korpf, GGM, and Gleason-Avery.

Warranty – Coal stoker stoves come with a myriad of different warranties.  Check to be certain the warranty which accompanies the stove is reasonable and covers most replacement parts.

image
KeyStoker Stoker

E. Some companies that make stoker stoves include

Leisure Line
http://www.leisurelinestoves.com/

Harman
http://www.harmanstoves.com

Alaska
http://www.alaskastove.com/

Keystoker
http://www.keystoker.com/

Reading
http://www.readingstove.com/




2) Batch or Hand Fired

A. Introduction
This type of coal stove is most similar in function to a wood stove, where coal must be added to the fire manually using a bucket or coal hood.  This is the type of coal stove that most people are familiar with and probably the most popular as well.  These coal stoves provide long heat output coupled with infrequent stoking and are a great heating choice for anyone considering coal heat for the first time.  Hand fired coal stoves should be firebrick or refractory lined and have a cast iron shaker grate or rotating grate to shake the ash from the burning coal bed.

B. Venting
Batch fed coal stoves must be hooked to a full chimney system, either masonry or class A; when installing a class A system or relining a masonry chimney for coal stove use, it is important to check with the manufacturer to be certain the pipe can be used with coal stoves.  Coal stoves deposit a thin coating of fly ash in the chimney that can mix with atmospheric water to become acidic and eat away at the liner, over time.  Because of this, even though no creosote is created when burning coal, the flue should still be swept yearly, to keep this ash accumulation and it’s undesirable side effects to a minimum.

image
Vigilant Coal (hand fired)


C. Lighting
Initiating a coal fire in this type of stove can be difficult because coal is hard to ignite; however once a fire is established a batch fed coal stove can run continuously from the beginning of the burning season until the end.  Below is a method of starting a coal fire which generally works very well, however individual stoves vary, so this procedure may have to be adjusted for your stove.

Start a new coal fire with a clean stove; while it’s possible to build a new coal fire on top of old coal, you’ll almost always have better results starting with a clean slate.  Begin the coal fire by getting the necessary wood kindling split and near the stove. 

Start a wood fire with small splits of kindling and perhaps some very small hardwood splits (finger sized or smaller).  Generally coal stoves only have one air control, which moderates the amount of air coming in underneath the fire through the grates.  However, some combination stoves may have a fire level air control as well as under-fire air.  During the start up time period, keep the under-fire air control wide open; it may also to be helpful to open the fire level air controls during the wood burning period as well.

Once the kindling is burning brightly, add some larger hardwood splits and continue to operate with the air controls wide open.  Don’t go to far from the stove at this point, although the point of the startup is to get the stove HOT, an unattended, wide open coal stove can become a dangerous overfire in short time.

Continue adding hardwood splits with the air controls fully open until the stove is fully heated, the chimney is drawing well and a good thick bed of glowing wood coals is on the grates of the stove.  At this point, you can began adding coal.  Add it VERY slowly at first, only two or three shovels full, depending on stove size.  If you opened the fire level air controls for startup shut them at this point and leave only the underfire air wide open. Allow this first thin layer of coal to begin burning very brightly and then add another, similarly thin layer of coal, again waiting for this layer to catch.

After this second layer of coal has caught, most of the grate area should be covered in glowing orange coal burning with an intense yellow or orange flame.  When this is present in the firebox, add a good layer of coal, approximately 3 inches in depth, of course depending on the depth of the firebox.  Continue burning with underfire air control fully open and waiting until this deeper layer of coal ignites and blue or yellow flames begin dancing on the top of the coal bed.  Once these flames are present, it’s generally safe to fill the stove to capacity with coal, which is usually just below the top of the firebricks, again, depending on the stove.  Follow the manufacturer’s instructions if they give a different maximum depth for the coal bed.

Leave the underfire air control open until the blue flames appear on top of the coal bed again and you can see glowing coal through the bed.  It is generally not necessary and sometimes unsafe to leave the air control open until the entire top of the coal bed is glowing.  At this point, set the air control for the desired heat output range and leave the stove alone for at least 8-12 hours.  Some larger coal stoves will burn even longer than this without being stoked.  Remember that coal is not like wood, it does not respond well to being poked and prodded, because the coal burning reaction is somewhat different than that of wood.

D. Tending

About twice a day, you will have to stoke or tend your coal fire if you wish to keep the stove running.  Stoking a hand fired coal stove with a good bed of coals will only take 15-20 minutes of total time.  First, start by observing the fire; is it still burning brightly?  Is the entire top layer of coal still black or barely glowing? Great, you’ve still got a strong fire and reloading will be quick and easy.  Open the ash pan door and shake the coal fire with whatever shaking mechanism the stove has.  Quick, choppy strokes work best; shake until some small glowing pieces of coal fall through the grate.  Any more than that and you’re wasting fuel and risk putting out the fire.  Too little shaking and the fire will slowly smother itself over the next day.  Leave the air control open and go get a coal bucket full of coal.  Before going to get the coal, check the ash level in the pan and be certain it is not overflowing.  Letting ash building up near the grates can shorten their lifespan.

When you come back with the bucket of coal, the stove should be burning brightly and you should be able to open the feed door and throw the entire bucket in at once.  Use the backside of your shovel to level the coal bed and shut the door.  Leave the underfire air control open until blue or yellow flames begin dancing on top of the coal bed again.  At this point, you can shut the air control for you desired heat output and again, leave the stove alone.

Suppose you waiting too long since the last stoking and the fire looks like it’s weak and on the way out.  The top of the coal bed will probably be mostly ash and there may be some dead spots in the coal bed where the fire has been lost.  You are on your way to losing your coal fire, but don’t panic, with a little extra time you can revive it.  In this case, DO NOT shake the fire first.  You will almost definitely smother it as the ash in the bed collapses.  Instead, open the air control and let the coal bed gain some momentum.  Once what little coal is left begins burning better, add a thin layer of coal, much like you were starting a new coal fire.  Repeat this in a few layers, being patient to let the fresh coal catch.  Once you’ve regained a hot, active bed of coal shake the stove down, being slightly more aggressive on the shaker since most of the bed will be ash.  Once you’ve shaken the bed down hard, reload the stove to capacity, allow the fresh layer to catch with the air control open and then reset to your normal burn rate.

(written by Corie Podschelne)


Please rate this article by clicking once on the Like or Dislike box below:

« Back to Articles Index Page
Back to Hearth.com Home »