Why can’t I get a complete burn with this coal?

 
Mr.Ark
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Post by Mr.Ark » Mon. Dec. 03, 2018 10:00 am

I am a first time coal burner here with a Royall indoor coal/wood boiler. It has a deep V shaped firebox with bottom air, a little top air and shaker grates. The draft blower starts and stops with the aqua stat and seals tight when it closes. It probably runs 2-3 ten minute cycles on an average day.
This is my second attempt at burning TSC nut coal (or any coal) and this time I filled it up with 120 lbs (about to the top of the firebrick). It burned hard for about 8 hours and then I shook it and added another bag and went to bed. By morning when the pic was taken it seems as though the coal won’t burn completely to ashes. It’s still a little black in the middle like it went out. The coal bed was not going at all except for a little in the back.
Any thoughts as to why this might be or is this normal?

BTW the side that was out was the side with the little bit of the over the fire air. Did that effect it at all?
Thanks in advance!
Drew


 
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Post by Richard S. » Mon. Dec. 03, 2018 11:03 am

Typical design for most hand fire stoves is a deep box and grates from one end to the other. That allows for a deep bed of coal and plenty of air. I would suggest the size of the firebox you have is just too big length and width, this for example is the EFM boiler:
Image

Lots of posts like yours over the years and most of the units like yours labeled coal/wood never really work that well with coal. I beleive many people have modified them slightly and had more success. There is a saying. "You can burn wood in coal stove but you can't burn coal in a wood stove." The EFM unit I posted above is designed to burn coal first and foremost. It will burn wood but if you want to burn wood you'd be better off with something designed for wood for better efficiency.

As far as the overfire the only time you might want overfire air is to release any built up gases before opening the firebox, this can help prevent BOOM!. ;)

 
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Lightning
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Post by Lightning » Mon. Dec. 03, 2018 6:19 pm

Yikes. That fuel bed looks pretty well exhausted to me. How much was left after shaking it out? You burned 160 pounds of coal inside 18 hours? I'm not sure what to think about that. What are you heating?

The secondary air would effect the top of the fuel bed if it was blowing against it in that area.

 
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Post by coaledsweat » Mon. Dec. 03, 2018 6:25 pm

Burned right through it is what I see. You need to keep fresh coal on top at all times. When you have ash at the top like that, she's done.

 
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Lightning
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Post by Lightning » Mon. Dec. 03, 2018 6:29 pm

coaledsweat wrote:
Mon. Dec. 03, 2018 6:25 pm
Burned right through it is what I see. You need to keep fresh coal on top at all times. When you have ash at the top like that, she's done.
Roger that, partner!

 
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Post by Mr.Ark » Mon. Dec. 03, 2018 8:36 pm

Lightning wrote:
Mon. Dec. 03, 2018 6:19 pm
Yikes. That fuel bed looks pretty well exhausted to me. How much was left after shaking it out? You burned 160 pounds of coal inside 18 hours? I'm not sure what to think about that. What are you heating?

The secondary air would effect the top of the fuel bed if it was blowing against it in that area.
This is my new house/workshop.
That garage door on the end is 16’wide and 14’ tall. Pretty big bldg. The bad part about it is it was only 28 degrees (but very windy) the night that I burned it. So in a nut shell that coal is done for at that stage.
Should I have added more to keep it fresh and the bottom stuff eventually turns to powder then? I don’t know why it all stay together and doesn’t turn to ash.... any thoughts?
It seem like some of it will take off again and burn hard with the next batch of wood that is thrown on top. That leads me to believe that there was still some energy left in it.
Thanks again.

 
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Post by Mr.Ark » Mon. Dec. 03, 2018 8:37 pm

Lightning wrote:
Mon. Dec. 03, 2018 6:29 pm
Roger that, partner!
How come the ash seems so hard yet with a little black left in the middles of some of the chunks? Too much air by chance or not enough?


 
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Post by BunkerdCaddis » Mon. Dec. 03, 2018 8:48 pm

I had a Mahoning Outdoor Boiler for about 15 years and burned coal in it one winter. I didn't know much at all about burning coal but it got us through when I ran out of wood. I used stove size coal in it and filled almost to the bottom of the door. I think you will have better results with a larger coal and a fuller load. Don't shake too aggressively, keep some ash on the grates.

 
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Post by Lightning » Mon. Dec. 03, 2018 9:19 pm

Mr.Ark wrote:
Mon. Dec. 03, 2018 8:37 pm
How come the ash seems so hard yet with a little black left in the middles of some of the chunks? Too much air by chance or not enough?
The only time a charge of coal will burn out into a fine ash is in the antique stoves because their fire pots are so well insulated, or so I've learned from the antique stove crowd. In the fire bed of pretty much anything else there is too much heat sink happening and as the fire runs out of fuel and cools, it extinguishes before all of the coal can be consumed. That's the nuts and bolts of it anyways, the way I understand it.

I see now why you burned up that charge in such a short time frame. That building is enormous :)

 
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Post by Mr.Ark » Mon. Dec. 03, 2018 9:29 pm

Lightning wrote:
Mon. Dec. 03, 2018 9:19 pm
The only time a charge of coal will burn out into a fine ash is in the antique stoves because their fire pots are so well insulated, or so I've learned from the antique stove crowd. In the fire bed of pretty much anything else there is too much heat sink happening and as the fire runs out of fuel and cools, it extinguishes before all of the coal can be consumed. That's the nuts and bolts of it anyways, the way I understand it.

I see now why you burned up that charge in such a short time frame. That building is enormous :)
So you would say that it’s pretty well burned up other then around the edges?
Maybe next time I should make the pile deeper?? And then keep adding to it more often?

 
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Post by CapeCoaler » Mon. Dec. 03, 2018 10:39 pm

How deep was the coal in the first picture...
6-8 inches...
Any pictures of it clear of ash...
Yes in the beginning adding coal every 8-12 hours...
Will help keep the burn going...
Heat loss calculation for that building...
How well insulated is the house portion...
And the shop...

 
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Post by Mr.Ark » Mon. Dec. 03, 2018 11:11 pm

CapeCoaler wrote:
Mon. Dec. 03, 2018 10:39 pm
How deep was the coal in the first picture...
6-8 inches...
yes about 8”
Any pictures of it clear of ash... Yes in the beginning adding coal every 8-12 hours...
Will help keep the burn going...
Heat loss calculation for that building...
i think about 190k per hour with a 70 degree rise.
How well insulated is the house portion...
house is the front third. Two story and spray foamed with closed cell to r-24
And the shop...r-25 Fiberglass in the Wall. All ceilings are r-49
It’s very well insulated and has a lot of spray foam. Above the shop is a room in attic apartment that I’m currently living in until the house side get finished.
The coal burn in the pic was a night that needed a 35-40 degree heat rise. But very windy also.
It seems like the coal just doesn’t want to burn all the way down. Maybe I just need to keep it going longer and keep it deeper. Or perhaps close the two small above fire air holes.

 
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Post by CapeCoaler » Tue. Dec. 04, 2018 12:20 am

Above fire air should be minimal...
Get it to 10" deep...
Shake grates till you see an orange glow below...
Add coal to maintain 10" coal depth...
Make sure the overhead door is well sealed from wind...
If the 190k btu/hr calculation is correct...
You would easily burn thru the 120 pounds of coal...

 
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Post by milw boiler » Tue. Dec. 04, 2018 1:39 am

This boiler will not burn coal as is. I know because I had the forunner to your boiler...the Energy Mate. The V grate is the problem. Coal needs a straight sided chamber with shaker grates & good over & under fire air. I spoke to the owner of Decton Iron works(Russell) & he told me my only hope was to make a straight sided insert. Still got to get air underneath the coal though. He said a square foot grate will give 100,000 btu's on anthracite so your loss of space is no big deal. Royal made shaker grates for the V grate years ago. Later Royals were all straight sided chambers with shaker grates...huge amount of grate area on these. Good luck!

 
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Post by Lightning » Tue. Dec. 04, 2018 4:25 am

Mr.Ark wrote:
Mon. Dec. 03, 2018 9:29 pm
So you would say that it’s pretty well burned up other then around the edges?
Maybe next time I should make the pile deeper?? And then keep adding to it more often?
Yes on all three. Also, a mix of stove and nut size coal will burn better at more depth.
milw boiler wrote:
Tue. Dec. 04, 2018 1:39 am
The V grate is the problem. Coal needs a straight sided chamber
Sorry but I disagree. I've been running anthracite in my "V" shaped fire box for 8 years as have others longer than me. It just takes some technique at tending to persuade ash not to cling and build up along the angled sides. It's not a problem. I'll agree that the straight sided fire boxes would be more forgiving in the ash clearing department.


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