Multi-Fuel Coal Stove from Europe/UK?

 
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Sunny Boy
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Post by Sunny Boy » Thu. Nov. 16, 2017 4:34 pm

gardener wrote:
Thu. Nov. 16, 2017 12:57 pm
It isn't that I want or prefer a European model. We have a unused wide fireplace in the basement. The choices here are large inserts, that I anticipate would produce more heat than I want. Or to put a small stove in the fireplace firebox, but all of the small coal stoves that I know of manufactured in the states are too tall for the fireplace.

I did see a number of European stoves that were more wide than tall, and I could take the legs off.
Also the heat output rating is lower, be more in line with how I expect to use it.

My current idea is to get a Hitzer or Keystoker insert, and idle it as low as is reasonable.
Unlike wood stoves, you can idle a coal stove (with a firebox liner ) way down until the draft just about stops, and it doesn't affect coal burning efficiency. It just runs that much longer before needing refueling. Many of the more efficient types can run so low that you can put your hand on the stove pipe only a few feet from the stove.

Then when you need extra heat in bitterly cold weather, the stove has the capacity to keep up with it.

That slow running ability of coal lets you use a larger coal stove and not give up efficiency.

Paul


 
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Post by gardener » Fri. Nov. 17, 2017 9:42 am

Sunny Boy wrote:
Thu. Nov. 16, 2017 4:34 pm
Unlike wood stoves, you can idle a coal stove (with a firebox liner ) way down until the draft just about stops, and it doesn't affect coal burning efficiency. ... Many of the more efficient types can run so low that ...

That slow running ability of coal lets you use a larger coal stove and not give up efficiency.
You stroked an aspect of coal stoves I am very curious about! (efficiency)
What is a firebox liner? (is it the firebricks)

Back when I was looking at the Hitzer 983, I was still learning about the EPA certified wood stoves/inserts. I had wondered whether there was an equivalent jump in efficiency in coal stoves that the wood stoves experienced in recent decades. The Hitzer 983 does have a baffle, and it increases its efficiency by forcing the exhaust to take a longer path to the flue and heating the stove walls more in the process. Whereas on the EPA wood stoves the point of the baffle is to reflect the heat back to the firebox to inject oxygen above the fire to burn off the volatile gases that would otherwise escape up the flue. I'm saying all of this to ask this:
Is there any such parallel technology on coal stoves to increase the efficiency?
Does anthracite coal have volatile gases?
What makes a coal stove more or less efficient?

As far as idling is concerning, I know of the Hitzer 983 (hand fed), it has three grates, and the Hitzer 503 (hopper fed) has two grates. I was wondering if there are solid replacement pieces to the grates to bring the units down to just one grate. Wouldn't that idle the unit down further?

Maybe I should start a new thread for these questions?

 
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Post by freetown fred » Fri. Nov. 17, 2017 9:45 am

G, people have blocked off grates in the HITZERS with firebrick placed on a slant not to interfere with existing grates. I'm thinkin once you get the hang of it, you'll be surprised how low you can idle down without this method--if not, like I said, it's been done.

 
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Post by Sunny Boy » Fri. Nov. 17, 2017 10:28 am

gardener wrote:
Fri. Nov. 17, 2017 9:42 am
You stroked an aspect of coal stoves I am very curious about! (efficiency)
What is a firebox liner? (is it the firebricks)

Back when I was looking at the Hitzer 983, I was still learning about the EPA certified wood stoves/inserts. I had wondered whether there was an equivalent jump in efficiency in coal stoves that the wood stoves experienced in recent decades. The Hitzer 983 does have a baffle, and it increases its efficiency by forcing the exhaust to take a longer path to the flue and heating the stove walls more in the process. Whereas on the EPA wood stoves the point of the baffle is to reflect the heat back to the firebox to inject oxygen above the fire to burn off the volatile gases that would otherwise escape up the flue. I'm saying all of this to ask this:
Is there any such parallel technology on coal stoves to increase the efficiency?
Does anthracite coal have volatile gases?
What makes a coal stove more or less efficient?

As far as idling is concerning, I know of the Hitzer 983 (hand fed), it has three grates, and the Hitzer 503 (hopper fed) has two grates. I was wondering if there are solid replacement pieces to the grates to bring the units down to just one grate. Wouldn't that idle the unit down further?

Maybe I should start a new thread for these questions?

The "liners" can be either cast firebricks, cast refractory, or ram-set refractory that is a sticky form of refractory cement that is rolled out like thick pie crust, cut into pieces to fit, and hammered into place in the firebox/firepot. Then allowed to air dry for at least 24 hours and then heat cured with a couple of small kindling fires. Coal burns best in a very hot fire. By insulating the sides of the firebox/firepot to keep the coal bed hotter it will burn more efficiently without having to run with as much damper opening as it would without a liner.

Some of the antique base burners, called "suspended firepot" designs, "wash" the outside of the firepot (which is suspended inside the stove body) in hot gases by channeling the hot exhaust down around the outside of the firepot and then up through ducts to the stove exit. That type does not need a liner and it is an extremely efficient design that, as far as I know, is not used in any modern stoves.

Wood stove efficiency is rated at the stove's maximum burn rate because that's where the most burning off of the waste gases occurs. Otherwise wood stoves send a lot of potential fuel in liquid and gas form up the chimney. Remember all the thick, white smoke the early "air tight" stoves put out when owners tried to run them slow to get longer burns ? That's wasted fuel/heat going "up in smoke".

Anthracite coal stoves are most efficient when the coal bed is kept as deep as possible, no matter if the dampers are set for idle, or for maximum heat output. Like wood stoves, many purpose-built coal stoves provide secondary air to burn off gases in a number of ways. Either though an adjustable secondary damper system, a fixed secondary air feed hole system, or as with many of the antiques, by not making them as "air tight" as today's stoves.

Anthracite does not produce deposits like wood stove creosote, or soot that some bit stoves do if they are not run hot enough. Therefore, since you don't have to run it hot to burn off those byproducts to prevent them from condensing and building up in a chimney system, you can damper a large anthracite stove down to idle just like a small stove at medium output. If you have a good drafting chimney system, it only has to stay warmer than outside the chimney enough to keep a draft going. That often means a good anthracite stove can be idled down to pipe surface temps in the very low 100F range.

Any place that air can bypass the firebed, going from under the grates to the stove collar, will make the fire sluggish or stall and die out. To reduce the firebox of an anthracite stove, you have to block off and reduce firebed width while keeping the full depth of the firebed. Depth is very important with maintaining a controllable and efficient anthracite firebed . Many newbies don't get/keep it deep enough because they think it will get too hot.

As Fred said, adding some firebricks to the sides of the firebox, to reduce the firebed width, while keeping the depth, is a common way to cut back the heat output in the shoulder months.

Paul

 
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Post by freetown fred » Fri. Nov. 17, 2017 11:32 am

Paul, if ya do to the sides, it will interfere with the grate function/action. If he's interested I'll explain better on the method I'm familiar with blocking 1 or 2 of the rear grates--depending on model.

 
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Post by gardener » Fri. Nov. 17, 2017 1:57 pm

Thank you guys, love this forum!
I will need to ponder that, sure to have follow up questions.
freetown fred wrote:
Fri. Nov. 17, 2017 9:45 am
G, people have blocked off grates in the HITZERS with firebrick placed on a slant not to interfere with existing grates. I'm thinkin once you get the hang of it, you'll be surprised how low you can idle down without this method--if not, like I said, it's been done.
Seems like a simple mod. Now I feel silly for asking. :baby:
So is the low idle more to do with how much air flow is allowed through the air controls, rather than the amount of grate space?

 
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Post by windyhill4.2 » Fri. Nov. 17, 2017 2:04 pm

My handfed stove is different than your unit,but when i want it to put out less heat,i just don't clear the ashes very good. When i need heat,i shake ashes every 12 hrs, when i don't need all the heat,i shake only in the pm so it will burn hotter thru the nite. I skip the am shaking of the ashes which slows the fire for the daytime when less heat is needed.No modifications needed for this method.


 
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Post by Sunny Boy » Fri. Nov. 17, 2017 2:24 pm

There are a few ways to control a coal stove's heat output. The stove design will work better with some methods than others.

1. Air damper controls. This is the most common way. Primary air, secondary air, MPD (Manual Pipe Damper) and check dampers or barometric damper.

2. Coal size. By changing the size of the coal, you change the air spaces between the coal pieces. Smaller pieces = smaller spaces = more resistance to air flow and a slower fire with less heat output. Big pieces = big spaces = more air flow and a faster burning fire with more heat volume.

Because I cook with my range, during the day I use the larger pieces of nut coal, dug from the outer edges of the coal bin. As the coal drops off the delivery truck shute the bigger pieces roll more easily down the pile, so they are in higher concentration towards the outer edges of the pile. For night time, I dig from the middle of the bin where there is a higher concentration of smaller pieces because they don't roll down the pile so easily. Those smaller pieces put more coal density in the firebox for longer overnight runs, plus they increase air flow resistance through the firebed, which aids in slow running.

3. Down-size the firebox with firebricks, as Fred pointed out. But, as Fred also pointed out you have to put the bricks where they won't interfere with the grates.

4. As Windy Hill pointed out, let the firebed ash up more to make it run slower. But, depending on the stove's primary air feed design, this may cause uneven airflow through the bed, resulting in some dead spots with unburned coal.

Paul

 
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Post by gardener » Mon. Nov. 20, 2017 8:48 am

Okay, after pondering all the responses. (Thank you, everyone.)
It seems from Paul's (Sunny Boy) responses draft is/will be an issue if I am going to try to idle the coal stove/insert.
Sunny Boy wrote:
Thu. Nov. 16, 2017 4:34 pm
Unlike wood stoves, you can idle a coal stove (with a firebox liner ) way down until the draft just about stops, and it doesn't affect coal burning efficiency. It just runs that much longer before needing refueling. Many of the more efficient types can run so low that you can put your hand on the stove pipe only a few feet from the stove.
Sunny Boy wrote:
Fri. Nov. 17, 2017 10:28 am
If you have a good drafting chimney system, it only has to stay warmer than outside the chimney enough to keep a draft going. That often means a good anthracite stove can be idled down to pipe surface temps in the very low 100F range.
My basement fireplace, where I want the coal stove/insert, the distance from the fireplace damper to top of clay tile flue is about 25 feet.
I envision using the coal stove/insert primarily during December, January, February.
The basement fireplace is wide, has a smoke shelf about 2/3 the size of the firebox, narrows to the flue, which is a 12x12 square clay tiled, or 11.25" square actual void. Not knowing much about fireplaces, I find it notable that the cement walls in the smoke chamber are very smooth. Anyways, what I am getting at is this:

What should be my goal for a flue?

a) vent to the damper and seal off with rockwool
b) vent to the damper and seal off with rockwool, attach a top plate with port same size as exhaust on stove/insert
c) full reline with flexible liner the size of the exhaust port on stove/insert

If I am burning during the coldest months, would draft be an issue if I just vent directly to the existing flue?
I get that having a flue that is the same diameter as the stove/insert exhaust the entire length is the best choice, but if I idle the stove/insert, isn't that nearly the same as exhausting to an oversized flue?

 
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Post by freetown fred » Mon. Nov. 20, 2017 9:39 am

G, as long as you get the stove pipe into the flu tile, at least a foot or so--flex pipe or something workable--you will be good. Do you have a cap on top of the chimney--something to consider.

 
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Post by franco b » Mon. Nov. 20, 2017 9:41 am

If your fireplace is interior then it will probably draft well.

If on outside wall, test with a lit piece of paper to see how it draws cold.

Sealing at the damper with rock wool or fiberglass is the easiest way and adequate.

 
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Post by gardener » Mon. Nov. 20, 2017 10:51 am

The fireplace / chimney is in the center of the house.
Each flue has a rain cap.

 
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Post by Sunny Boy » Mon. Nov. 20, 2017 12:59 pm

gardener wrote:
Mon. Nov. 20, 2017 8:48 am
Okay, after pondering all the responses. (Thank you, everyone.)
It seems from Paul's (Sunny Boy) responses draft is/will be an issue if I am going to try to idle the coal stove/insert.





My basement fireplace, where I want the coal stove/insert, the distance from the fireplace damper to top of clay tile flue is about 25 feet.
I envision using the coal stove/insert primarily during December, January, February.
The basement fireplace is wide, has a smoke shelf about 2/3 the size of the firebox, narrows to the flue, which is a 12x12 square clay tiled, or 11.25" square actual void. Not knowing much about fireplaces, I find it notable that the cement walls in the smoke chamber are very smooth. Anyways, what I am getting at is this:

What should be my goal for a flue?

a) vent to the damper and seal off with rockwool
b) vent to the damper and seal off with rockwool, attach a top plate with port same size as exhaust on stove/insert
c) full reline with flexible liner the size of the exhaust port on stove/insert

If I am burning during the coldest months, would draft be an issue if I just vent directly to the existing flue?
I get that having a flue that is the same diameter as the stove/insert exhaust the entire length is the best choice, but if I idle the stove/insert, isn't that nearly the same as exhausting to an oversized flue?
My range is piped into the original kitchen range chimney thimble in the kitchen's outside wall. It's about 37 feet tall and unlined brick chimney, that is typical of the late 1800's around here. That same chimney also had a coal hot water heater piped into it in the basement. But that thimble has been capped off.

The inside of the chimney is 8-1/2 inches square. My range has a small firebox that only holds about 20-25 pounds of coal.

With a flue cross section that large and such a small heat volume firebox, I have no trouble idling a coal fire down to the point where a wood fire will go out.

Dampered down for long burns overnight, when I come down in the morning, the plates over the firebox are somewhere in the 600 F range. 24 inches up from the stove top the pipe surface temp is in the low 100's. Some mornings the plates are in the mid to upper 500F range and the pipe is down to100-110F. The mano reading is always .005. That's two zeros to the right of the decimal point. In 13 years, of running 24/7 for about 9 months of each year, I've never had the range stall out running it that slowly.

With a larger firebox stove and a decent drafting chimney system, you should be able to run it slowly.

As Fred said, get the pipe up into the chimney then seal off around it well with fiberglass.

Or, as some do, cut a hole for a thimble into the chimney above the baffle plate and close the plate.

Paul

 
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Post by gardener » Wed. Nov. 22, 2017 2:13 pm

Sunny Boy wrote:
Fri. Nov. 17, 2017 10:28 am
The "liners" can be either cast firebricks, cast refractory, or ram-set refractory that is a sticky form of refractory cement that is rolled out like thick pie crust, cut into pieces to fit, and hammered into place in the firebox/firepot. Then allowed to air dry for at least 24 hours and then heat cured with a couple of small kindling fires. Coal burns best in a very hot fire. By insulating the sides of the firebox/firepot to keep the coal bed hotter it will burn more efficiently without having to run with as much damper opening as it would without a liner.

Some of the antique base burners, called "suspended firepot" designs, "wash" the outside of the firepot (which is suspended inside the stove body) in hot gases by channeling the hot exhaust down around the outside of the firepot and then up through ducts to the stove exit. That type does not need a liner and it is an extremely efficient design that, as far as I know, is not used in any modern stoves.
It seemed to me that the 'base burners' shown off on this forum have had the ram-set refractory added, as though it did not originally come with it when the units were new. I have not be careful to read the full threads when they are discussed, so correct my impression please.

You mention that some of the antique base burners are suspended firepot designs.
Is there a list of which manufacturer/models are?

 
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Post by Sunny Boy » Wed. Nov. 22, 2017 4:30 pm

With thousands of different makes and models of stoves built, I doubt there is a list of types.

Some, like Glenwood, offered several sizes, but they look very much like some of their cylinder stoves that were not suspended pot base burners. Same with other manufacturers.

And, many of the suspended pot base heaters are what we call "mica burners" - the stoves with many mica windows on three sides.

Paul


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