Comments1/7/15 

HOW I BUILD AND MAINTAIN A HEAHTHY BED OF HARD COAL

That lasts weeks, months or the entire season

This document only applies to burning anthracite coal in hand fired furnaces.  Stoker fired furnaces are a different beast altogether.  Also I have never burned soft coal.  Except for the fact that I would like to see more people succeed at heating with coal I have no agenda nor am I pushing any manufacturers stove, furnace or coal.  I'm doing a search for a new furnace I have noticed that even though there's allot more information on the internet now allot of it still has me scratching my head.  So I hope this can help you.  But unfortunately if your furnace is of poor design for coal then you will have limited results when it comes to maintaining the bed for extended periods.
What I expect from coal           My history and furnace           What I look for in a furnace            Conclusion            One last word on coal

Since most home systems burn nut size coal I am going to explain this using nut sized coal.  Please remember that the bed and grates I have are really a bit to large to burn 100% nut coal although I have burned it exclusively a few years.  One of the nice things about burning coal is that a few times over the years when old houses have being torn down or remodeled I have been given free coal.  The last time that happened I got 4 free tons.  Anyway, your bed and furnace might not be as big nor will your weather, geography or any other factor be the same but the principles and steps are the essentially the same.  Every stove/furnace and situation is different so in the end it will take a bit of time to get used to.  But I believe if you follow the steps below you will make it a much easier and a less frustrating learning experience.  Actually it is like allot of things.  If you keep it simple, follow the steps, don't become engrossed on the cost of the coal you are feeding the furnace and don't over think it, it's easy and you'll be heating your home with coal right off the bat!


My History:

I live in Maine where we can get -10 degree or below night time temps a few times a year.  I have been heating my house with anthracite coal for 30 years.  When I first started buying it it was $55/ton.  Our house is a modest 44'x24' split level ranch style home.

My first attempt at burning coal was with a standard wood stove similar to an Allnighter with no grates.  Of course I could burn coal in it but I had to start new every day and the fire was hard to control.  Not exactly what I was looking for.

My second attempt went better and was with a "KingCoal" (similar to a Wonderluxe) stove if memory serves.  I built a plenum over it and the heat went straight upstairs through one vent in the center of the house and spread to the rest of the house.  It was great but there were a couple of drawbacks.  One was that there should have been another grate under the ash instead of the fairly substantual cast iron lips on each side of the grates that impeded the free fall of ash to the pan and caused problems.  To remedy this I had to regularly run a poker through the ash that built up and in doing so created clinkers.  For that I had to let the fire burn out and clean all the ash and coal out and start over every couple weeks or so if I remember correctly.  Very inconvenient!  Our other problem or should I say more of an inconvenience being that the thermostat was attached directly on the decorative shell of the stove and had to be adjusted (manually) allot.  So we spent those years running around in tee shirts and shorts all winter.
This was although a perfect size stove that heated quickly and the bed of coals was all in all easy to maintain.  If I could convert the thermostat system to conventional 24v upstairs thermostat with a motor to raise and lower the damper as last resort I could settle for this stove to heat my house, simple and relatively cheap.

Finally we got an Olson Duomatic CWO-B140 (140,000 BTU's) conventional heating system ducted to every room.  It is a monster in size and really about 50% bigger in BTU's than we need but it works well and we have enjoyed it for the past 24 years.  We heat the house to 72 degrees and use about 3 tons of stove size coal a year, maybe 1/2 -1 cord of wood and a little bit of fuel oil.  It is in the basement and our floors are nice and warm and the temperature in the house is always even.  It's controlled by separate thermostats.  One for oil and the other for coal and wood.  Not really sure the size of the entire chamber but the bed area is firebrick lined on all four sides, straight down to the shaker grates.  The bed itself is something like 15" wide x 18" length x 16" deep.  The furnace has 3 heavy cast iron shaker grates.  My furnace is rated for stove size coal but at times I've burnt a 3/4 to 1/4 mix of stove and nut size respectively.
What a shame the company stopped making this furnace.  It is in my opinion an ideal multifuel furnace for all the reasons I've just stated and more.  The coal bed calling for the draft it needs works well.  The only drawback I can think of with this furnace is that the chamber is only slightly over 1/16" in thickness (14 gauge).  But on the plus side of that is the fact that it transfers heat quickly, has lasted 24 years and I hope to get a few more out of it.  And as you can see I have the furnace plummed to the water heater so from mid November to the beginning of April hot water is free.


START THE FIRE:

1.  Crumple up some paper and get some kindling going.  Once that is going throw in around 6 sticks of larger split hardwood at least 1"-2"s side to side or something like that.  Close the fuel door to your furnace but leave the ash door open and give it 10 minutes or however long it takes to start embering.  Or start a wood fire and wait for it to burn down to a glowing bed of coals.

2.  When the fire is raging and you can see the glowing embers on the wood start layering coal on top of it.  At this point you won't be able to get an even layer (unless you started with a bed of glowing embers) because it will be falling through the wood.  Just layer it in the best you can making sure not to smother it completely.  This first time you want to see some exposed wood with large flames coming up though the coal in places.  Now close the fuel door but leave the ash door open again.  And leave it for 10-15 minutes.  Usually 15 minutes is better.

3.  By this time you should see at least some of the coals starting to glow on their edges.  If you left it too long in one of these layering steps and all the coal is white hot, load a slightly heavier load than in step 2 and pretty much completely cover it.  Otherwise start the process over again and load on 1"-2" of coal.  Again it helps to leave it so there are some small flames coming up through the coal in spots during the rest of the layering steps.  Close the fuel door but leave the ash door open again for 10 - 15 minutes.

4.  It usually takes me 4 or 5 layers until I get the depth I want.  By this time I have a large mass of glowing red coals going that I can see in the bed so on the last layer I just cover the bed completely to the level I want not worrying about flames coming up through the bed.  The amount of coal you layer each time and number of layers you do may be different.  Close the ash door and don't forget to set your thermostat or draft damper where you want it.

In the early and late fall and winters I run a nine inch deep bed.  During the coldest days in January and February it will be a 12" deep bed.  And remember that depth always includes the ash that is there at the bottom of the bed.  I start the season using about 35-40 lbs a day and during the coldest period it can be up to 80 lbs a day.  I store my coal outside and bring it in the 5 gallon buckets.  I also have a small building/bin for loose coal that holds 3 ton but it needs some work to the sills before I can use it again.


MAINTENANCE:
With regard to a flat level bed I refer to below, in all likelyhood you may be building a mound for your bed or building a mound against a hearth plate or firebricks (banking).

1.  In the morning the first thing I do is empty the ashes from the night before then I shake the grates around 10 times each going back and forth between grates until I see a glow in the ash pan and a level bed of coals.  I close the fuel door while shaking.  But I open it and visually check the bed during shaking because some coals will frequently drop through the grates prematurely and one grate may need more shaking than another.  I don't want to shake them so hard that all the coal starts falling through the grates nor so softly that nothing really happens.  Nor do I want to shake down all the ash because it protects the grates from excessive heat that could damage them over time.  But the bed should shrink in size.  I close the ash door when I've shook enough down.  Then I just fill the stove with the level of coal I want covering the bed entirely.  I don't worry about leaving spots for the flames to come up through like when starting the fire.  Next close the fuel door of course.
The shake down is probably the hardest thing to explain and it does take time to get a feel for it.  For me it is usually a combination of seeing a glow in the pan which is small pieces of coal scattered through the ash in the pan and the bed going down the amount I know it should for the temperatures and conditions..

2.  When I get done of work I empty the ashes from the morning.  Put the pan back in and shake it down some more.  Not as much as in the morning though.  Close the ash door and scatter 3-4 shovels on the bed. .

3.  Before I go to bed (no need to empty the small amount of ashes in the pan right now) I shake the coal down like in the morning but usually more as it is colder and often windier at night and fill it up to the level I want creating a nice flat level bed again.

Obviously as the weather grows colder the amounts of coal I layer on in each step becomes exaggerated.  But that's it, my routine.  It takes less than five minutes three times a day.


Other hints:

Anthracite coal likes a deep wide bed.  The smaller the bed of burning coals the harder it is to maintain the bed for any amount of time.

Like you have read NEVER poke, slice or disturb a coal fire and also NEVER try to move it to bank it.

Coal doesn't burn to a fine ash unfortunately and maybe that helps cause clinker formation?  Some are smooth and round but most are rough and irregular.  I once pulled one out of the ash that was as big and smooth as a baseball although they do not normally look like that.  They have formed when I had an extremely hot coal fire or I was forced to poke and disturb the coal while trying to get the ash to drop. 

Coal must have the air introduced beneath the bed.  The entire bed/shaker grates need to be covered with coal so that the air is forced up through the coal.

Coal makes allot of ash, much more than wood and you may and will probably want to empty the pan more than once per day.

At times when I've left the ash door open and come back to a mound of coals raging hot I have done one of two things.  Either cover it in ash or cover it in coal.  I only ever smothered it in ash once.  It worked well but just seemed counter productive because I'm not usually trying to kill the fire, just bring it back under control.

I live in a 2x4 constructed home with standard insulation and need nights and/or days near thirty degrees or below to be comforatble.  It becomes very hard to keep a bed going with a few days of forty degree temperatures.

Allot of what you read on the internet like about coal fires lasting up to 20 or 30 hours is true.  It can be done easily but the stove will stop producing heat long before that last piece of coal dies out and you will have to shovel it out and start the fire new again.  It is a daily routine with some stoves like the old potbellies you've seen.  Also, I have never been able to keep a nice bed of coal going for an acceptable period of time by loading the coal twice a day and believe me I have tried enough times.  Maybe it's our colder winters, my stove and furnace or me.  I tend the fire 3 times a day and for example last winter I started mid November and I was still burning the same bed of coals when in February it finally dawned on me that I should really clean the furnace out and get any clinkers out of there if there are any.  I don't usually like to let it go that long.  But having said that I have gone many seasons on one bed of coals.  I can usually tell if there are any large clinkers because there will be an area in the bed where the coals just won't fall as they should each time I tend the furnace. 
Anyway that is what I want, an easy to maintain bed of coals that will last for weeks or months with as little effort as possible.  I myself would rather just maintain the stove than have to go through cleaning everything out and starting from scratch all the time.  Coal is hard enough to burn so even if you follow all these suggestion there will be times where you will make mistakes like leaving the ash pan door open and overheating the house and then if you don't load more next time you may lose the fire and have to start over, not take the colder temperature into consideration and wake up cold and maybe you lost the fire again and the list goes on.  I still do it myself today on occasion.


WHAT I LOOK FOR IN A STOVE/FURNACE:

1.  A bed area that is not slanted and goes straight down to heavy cast iron shaker grates. 
I'd stay away from the so called shaker grates that slide back and forth against each other and I am not sure of the furnaces with the slanted beds especially if angle is shallow and the shaker grates are narrow.  Ash and coal doesn't always want to drop to the grates like it should even when it is a straight drop.  For a lack of a better way of describing it, ash and coal likes to make bridges.  Also if there is a break in the firebricks it will cause the ash to hang up more.  The ash tends to want to hang up on any ridges even on a vertical surface and will fuse to the edges of these ridges over time making them worse which doesn't really affect a vertical wall.  In fact I don't see any logic behind a slanted bed using wood or coal as I would have some of the same problems burning wood?  Who wants to deal with that, it's nuts.  I'm sure it is an Obama design to kill the industry.

2.  Firebricks on all sides of the bed.
Like the manufactures warn you.  The heavy cast iron shaker grates can warp from a coal fire being in direct contact with the grates all the time.  What do you think is going to happen to the thinner hearth plates some are putting in the ends of the bed exposed to the coals?  Of course if the bed is long enough you could mound the coal up in the center and the plates may not have enough heat transferred to them to do any damage.  But then to get your big mass you don't want to have to build the mound up over the level of the bricks exposing the steel walls of the chamber to intense damaging heat.   I have never seen this happen but I do take the advice as gospel.  And I haven't come upon any furnace or stoves that I thought if loaded properly you'd have that problem

3.  Chamber made of at least 10-14 gauge steel but not so thick that it takes hours to heat up and transfer heat.  In my opinion 1/4" would be too thick for me but then again it would probably last 100 years.

4.  24v thermostatic control of the draft damper to the under side of the bed of coals.
Manual control with a spin damper works well it's just that it takes allot more work to learn and effort to control the fire and temperature in your house and you won't get the fine control of a thermostatically controlled system.

5.  A blower to help the heat get into the house quicker.  You will burn less coal if your system is configured like a conventional hot air furnace.

4 and 5 are purely personal preference.

I see the new stoves are introducing 20% of the air on top of the bed.  In my opinion this is just another OBAMAMARE.  It is true coal gives off a small amount of burnable gases especially while heating up newly introduced coal but that doesn't last an appreciable amount of time and if there were any real benefit to it stove makers or owners would have taken advantage of this in the past few hundred years.  I could almost see it for the first 30 minutes but after that I can see no heating benefit of introducing cold air into the fire chamber except to cool the skin of the chamber and send cooler temperatures to your house?   Just my opinion, I could be wrong.


IN CONCLUSION:

Although I could burn wood in many coal stoves and furnaces, I do not believe that I could easily maintain a bed of coals in just any wood/coal stove or furnace.  The internet, forums, and manufacturers sites have a wealth of information and you'll learn allot but my best advice to anyone interested in heating with coal would be to make sure to talk to the people who actually sell coal and ask them questions about stoves, furnaces and burning it in general.  Lets face it, they want you as a longtime customer and absolutely want you to succeed.  Next when you finally nail down a potential candidate for a furnace go see it in a showroom or better yet find someone who owns one and talk to them and ask if you can see it in action.

Heating with coal the way we do is a little bit of work.  Certainly not as convenient as fuel oil, natural gas or propane.  On the other hand I like the fact that our floors are always warm and the temperature in the house is always even at about 72 degrees.  And during those years when the price of fuel has spiked like this last time to $4/gallon and people up here were paying thousands to heat their houses or like the majority turning their thermostats down to 60 degrees or less and running around with sweat suits and long underware indoors all winter.  Well let me just say coal has worked well for us.

So just remember it's not rocket science and I wish you the best of luck!




One last thing:  There is one coal company that I stay away from now, but at the time it was all I could get.  Three years of them and I was ready to quit heating with coal and go back to oil.  Surprisingly you may think of their name as synonymous with coal.  They sell the worst and dirtiest coal I have ever experienced.  It's like they somehow discovered how to make the coal dust stick to the nuggets of coal.  Each nugget is like heavily breaded with coal dust.  Also, the bags never appeared to be uniform in weights.  Many of the 40lb bags wouldn't fill a five gallon bucket.  But the worst was the sorting.  Their coal was alway larger than any other companies I had burned and it made it difficult to build uniform beds and it just plain looked bad.  Every year I would get at least one ton in which there would be huge chunks of coal in each bag and I mean big!  In those three years I got two tons where literally every bag had 2-3 the size of softballs.  You never knew what you were going to get but for me it was consistently bad.  One quarter of a bag could be filled with dust and pea coal and the rest, all sizes up to nerf footballs.  So I regularly used chestnut coal just to try to make the bed level and fill the huge pockets.  I had the some of the same problems with the chestnut.



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