Masonry Fireplace w/Coal?

Masonry Fireplace w/Coal?

PostBy: JRLearned On: Mon Aug 19, 2013 2:13 pm

Has anyone built one of these for Coal? http://www.mha-net.org/

It seems to me that coal would be excellently suited to transfer it's heat to a thermal mass of stone and mortar much better than wood. I'm just wondering if you took a standard hearth and built it out and up floor to ceiling with a huger thermal mass, and built into it a fire box w/fire brick, fire door, ash door, shaker assembly, etc if you'd have this super efficient storage of heat in your basement compared to a free-standing stove.

Would it be literally the last stove you ever buy so to speak?
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Masonry Fireplace w/Coal?

PostBy: nortcan On: Mon Aug 19, 2013 2:40 pm

These ""foyers de masse" are very effective but you build only 1 or 2 hot and short fires a day and let the fire dies. The heat you transfer to the mass is slowly sent back to the house. Exactly the opposite to the big advantage of burning anth that burns steadily 24/24. Then you can controll the heat output according to the outside weather changes. A mass heater reacts very very slowly, you get the heat only many hours after the fire is dead.... Plus are very heavy and cost a few $$$ and are more efficient in an open area.
One day I was in the house of a custommer of mine, having a ""foyer de masse"" and the fire was out like it's supposed to be, I did touched the outside of the bricks and it was just a little warm. Not warm enough for me :)

Hum, maybe a little on the Antique's side or ""easy coal street"" like some call it :lol: but these Antique give you what you paid for and much more...
nortcan
 
Stove/Furnace Make: Stuart,Peterson/ Grander
Stove/Furnace Model: Sunnyside/ Golden Bride

Re: Masonry Fireplace w/Coal?

PostBy: alfort On: Mon Aug 19, 2013 3:09 pm

I sold my house a couple of years ago that had a masonry heater in it. It was made as a kit by TuliKivi out of 100% soapstone. It heated 3500 square feet in upstate NY with no problem. They don't burn coal. The fire has to be burnt hot and fast and then go out. Mine was the largest they made when I built the house. The house was well suited for it and the heat circulated very naturally. Once you learn how to use it (just like learning how to use a coal stove) you know when to build a rip-roaring fire or just a smaller one. You never let them smolder, and let them go out after the recommended burn time. You don't necessarily have to burn it the max amount of time. I watched the weather reports and burnt the fires accordingly. The heat radiated off it all day and night, was great and you don't have to worry about leaving the house with a fire burning. Didn't have to clean a chimney either (20 years). It burnt so hot and clean there was no creosote build up. I really miss it, but I've got two Glenwoods to restore, someday.
alfort
 
Hand Fed Coal Stove: Glenwood Modern Oak 118, Glenwood Cabinet C
Baseburners & Antiques: Glenwood Modern Oak 118, Glenwood Cabinet C

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Re: Masonry Fireplace w/Coal?

PostBy: JRLearned On: Mon Aug 19, 2013 5:04 pm

Great information and actual experiences with these. One of the principles of coal stoves is the thermal mass and surface area that the cast iron provides. That is, the bigger and heavier the stove the better because it helps radiate the heat. For instance, my U.S. Army cannon heater (in storage in the garage currently) is a massively heavy cast iron stove. Get it fired up and its stays hot for a long, long time even after the fire dies down. Put coal in it and you have a massively hot mass of cast iron that overpowers the room. So... in principle if burning in a hearth, coal or wood, the bigger and heavier the hearth, the more heat retention and efficiency right?

So why let the fire go out? What is the reason for this by design? What if you burned a small fire in one of these thermal mass hearths 24/7? What would happen?
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Masonry Fireplace w/Coal?

PostBy: franco b On: Mon Aug 19, 2013 5:27 pm

Nortcan and alfort explained it pretty well.

Wood burns cleanest with lots of air. When heated half the heat value is released as gas very quickly. Restricting air produces smoke. Lots of air means high stack temperatures. Massive heat absorbing masonry is able to compensate for the excess air. The very hot raging fire is clean. A small fire to burn as clean would have to be fed very frequently since air restriction combats the purpose of the stove and the smaller fire would not get the burn chamber near as hot for efficient burn.

Anthracite coal releases very little gas relative to wood. Air restriction of the burning carbon, like with charcoal works well so long clean burns are possible.

Any mass in excess of the structural integrity of the stove and burn pot is not good as the heat exchange properties are inferior to a thinner material.

Your Army cannon stove was built heavy to withstand rough handling and frequent over firing, not as a thermal sink.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Masonry Fireplace w/Coal?

PostBy: JRLearned On: Mon Aug 19, 2013 8:34 pm

franco b wrote:Any mass in excess of the structural integrity of the stove and burn pot is not good as the heat exchange properties are inferior to a thinner material.

Your Army cannon stove was built heavy to withstand rough handling and frequent over firing, not as a thermal sink.


There is another thread here that says surface area and temperature dictate btu output per hour: http://nepacrossroads.com/about10030.html

Is this not true? A large radiating surface area like a oversized potbelly with a large shroud would have a higher btu output per hour to the room than the same size fire contained in a coffee can. Am I wrong? Or are you just saying the thickness of material /mass is irrelevant? For instance, a really large coffee would be superior to a small one.
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Masonry Fireplace w/Coal?

PostBy: franco b On: Mon Aug 19, 2013 8:43 pm

JRLearned wrote:There is another thread here that says surface area and temperature dictate btu output per hour: Stove BTU output based on temp and surface area?

Yes it is true. But the thicker the steel or cast iron the more slowly it will transfer heat from the interior of the stove. On an antique Oak style stove which has both cast iron and much lighter steel in the upper heat exchange area, the steel will be hotter than the heavier cast iron and so emit more Btu. An aluminum or steel frying pan will transmit the heat of the flame faster than a cast iron fry pan but the cast pan will be more evenly heated because the slower heat transfer has time to spread laterally.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Masonry Fireplace w/Coal?

PostBy: JRLearned On: Tue Aug 20, 2013 8:46 am

I understand that wood is inefficient and a lot of heat is lost in the gases out the chimney in a normal fireplace or stove. These thermal mass heaters reclaim that heat and store in the stone and masonry. I've read on several sites online, people claiming a 90% reduction their wood consumption for heating their house. 3 or 4 cords a year down to 2/3's of a cord in one claim. From anyone who's had one, is that claim for real? It seems too good to be true.

So Franco B is saying the thermal mass stove is for wood because the aforementioned reclaimation of flue gas heat. Coal combustion gases don't have the temps and heat content of wood gases. That means most of the heat is conducted by the air and stove metal mass immediately surrounding and in contact with the fire chamber, which makes coal more efficient than wood. And it has a higher btu content anyway.

Ok so here's the next statement and question for Franco B to disprove ;) :
Given all of the above, there must be some benefit to storing the heat of a coal fire, even one that burns 24/7, in a thermal mass. Maybe that benefit is marginal, I don't know. But why can't we make a coal fire even more efficient by some means of thermal mass stove. To reclaim the heat from coal flue gas, maybe you need a smaller run of chambers and less reclaimation than you do with wood because the temperatures are lower, but there IS something there to reclaim if you tried. And, for the heat mass in the burn chamber, doesn't storage of that heat by surrounding it with a huge masonry mass do something beneficial? Perhaps you'd need a smaller coal fire going overnight as temperatures are dropping because the mass helps regulate things?
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Masonry Fireplace w/Coal?

PostBy: franco b On: Tue Aug 20, 2013 12:12 pm

Coal is not more efficient than wood. It's just that by the nature of coal the stoves we use come out that way. When wood is broken up into small pieces (pellets) and small amounts are fed slowly with proper air mixture very high efficiency is possible, as in some pellet stoves. You might even say that wood is more efficient than coal because of the much lower ash content, and getting rid of ash counts in terms of labor. What a pellet stove generates in a month might be the same as one day with a coal stove. So any difference is only by how the fuel is burned. With coal the labor of carting it for equal Btu is about half that of log wood by the pound, less for pellets or pressed wood bricks which are drier.

In the EPA approved stoves for wood, methods have been designed to introduce heated secondary air to consume the gas before it turns to smoke. If the flame from secondary air ports are blue that is gas burning, if yellow it is smoke burning. Efficiency has gone from 50 to 70 percent.

The masonry stoves are able to cope with the very large release of gas from wood by first burning it in a very hot clean fire with lots of air. The mass is able to keep the stack temperature from going too high. The same thing can and has been done with steel and cast iron stoves by adding more heat exchange surface but the heat is then rapidly transferred to the room in excess amounts and then goes cold as the fire goes out. The masonry stove with much less rapid heat transfer stays warm for long periods. A coal stove has no need of heat storage since the fire can be regulated to burn relatively long and slow. The heat is steady without large thermal mass.

In regard to stack temperature it is not wasted heat because you need it to generate draft and also to avoid condensation of very corrosive gasses along with the moisture present in the flue gas. So it is only too high temperature or too low that should be avoided. About 250 degrees all the way to the top of the chimney is about right. In that way a small stove is less efficient than a large since a higher percentage of the heat produced in the small stove goes up the chimney to maintain draft and adequate flue temperature.

Furnaces and boilers have been designed to run with very low stack temperatures. They are called condensing units because they do condense the flue gas and drain it away. Though outstandingly efficient they have their own set of problems dealing with that condensate. I remember years ago there was a problem with reactions with household cleaning products containing chlorine with a potential for deadly gas. Others would know more about this and modern condensing units than I but the point is a lot of things have been tried already with good and bad results. That's why it's so interesting to try different stoves with different designs.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Masonry Fireplace w/Coal?

PostBy: JRLearned On: Tue Aug 20, 2013 1:37 pm

A another great lesson from Franco B. Thanks again.
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Masonry Fireplace w/Coal?

PostBy: nortcan On: Tue Aug 20, 2013 1:48 pm

And if a stove burns 24/24, like in a coal stove, it's useless to stock heat in a stone mass. A stove should dies if you want to get the best part of the heated mass.
Many antique stoves and some new ones like the Vigll, have very long gases path to keep the heat Inside of the house and not in the chimney.
nortcan
 
Stove/Furnace Make: Stuart,Peterson/ Grander
Stove/Furnace Model: Sunnyside/ Golden Bride

Re: Masonry Fireplace w/Coal?

PostBy: just peter On: Tue Aug 20, 2013 5:07 pm

What about not using anthracite, but bituminous coal?
Last year i bought some bituminous coal to give it a try, the problem for me is, that when i do new coal in
the stove i got a raging fire, until all the gas is burnt.
Then the coal act like anthracite.
But meanwhile i roast out the house, open doors use "window stats", and the coal is not expensive,
but not cheap enough for that.

Peter.
just peter
 
Hand Fed Coal Stove: Weso 225 C3, unknown Altan
Coal Size/Type: bituminous coal,
Stove/Furnace Make: unknown, Weso
Stove/Furnace Model: Altan, 225C tile stove

Re: Masonry Fireplace w/Coal?

PostBy: franco b On: Tue Aug 20, 2013 5:46 pm

I have never burned bituminous but obviously the problem is similar to that of wood. A large amount of gas released on initial heating which if not burned creates smoke and soot and if burned makes too much heat.

The antiques intended for bit used hot secondary air to help burn the gas but I suspect they too left something to be desired. Forum member Berlin who has lots of experience with bit recommends a particular type stoker as the best solution. A stoker has the advantage of feeding just the right amount of coal for the air supplied, just as a pellet stove does for wood.

I would think a masonry stove designed for bit would work better than the usual steel or cast iron stove that lacks the ability to soak up excess heat for later use.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Masonry Fireplace w/Coal?

PostBy: just peter On: Tue Aug 20, 2013 6:10 pm

Thank you Franco,
These where my thougts to,i was playing with this idea for a while.
I think i have to made a little test set up.
Have to find some bricks first.

Peter.
just peter
 
Hand Fed Coal Stove: Weso 225 C3, unknown Altan
Coal Size/Type: bituminous coal,
Stove/Furnace Make: unknown, Weso
Stove/Furnace Model: Altan, 225C tile stove

Re: Masonry Fireplace w/Coal?

PostBy: franco b On: Tue Aug 20, 2013 6:31 pm

just peter wrote:Thank you Franco,
These where my thougts to,i was playing with this idea for a while.
I think i have to made a little test set up.
Have to find some bricks first.

Peter.

Making a test set up is not easy because the first order of business is to burn clean which means ideally a round chamber or segmented round and hot secondary air. Full thick fire brick.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

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