31,500 output BTU's / 0.75 (for 75% efficiency) = 42,000 input BTU's (half of the full rated 84,000)

42,000 BTU's/Hr. / 12,150 BTU's/Lb. = 3.46 lbs. per hour

24 hours x 3.46 lbs./Hr. = 83 lbs.

If burning 2.5 lbs/Hr. gives you 525 surface degrees, what would 3.46 Lbs./Hr. be giving you in the same stove (if combustion efficiency remains the same)? That's 38.4% more coal being burned per hour. I would surmise that the extra 38.4% would have the stove hovering around 700 degrees.

42,000 BTU's/Hr. / 12,150 BTU's/Lb. = 3.46 lbs. per hour

24 hours x 3.46 lbs./Hr. = 83 lbs.

If burning 2.5 lbs/Hr. gives you 525 surface degrees, what would 3.46 Lbs./Hr. be giving you in the same stove (if combustion efficiency remains the same)? That's 38.4% more coal being burned per hour. I would surmise that the extra 38.4% would have the stove hovering around 700 degrees.

- lsayre
**Stoker Coal Boiler:**AHS S130 Coal Gun**Coal Size/Type:**Blaschak Anthracite Pea**Other Heating:**Resistance Boiler (13.5 KW)

Larry,there is no way in hell I could run over 100 or 120 LB's in 24 hrs or the stove would be 750 or 800*.The coldest day this year I used just a bit over 73# in 24 Hrs for the 3 coldest days with the stove running about 610 to 625*.I don't know about the BTU ratings for the stoves(at a 100% efficiency I would need to burn over 190# a day to get 100,000 BTUs so in my opinion theres no way for the 983 to run that high) but I think its BS,all I know is that it heats the house pretty dam good so if I am missing something please tell me .Keepaeyeonit

- Keepaeyeonit
**Hand Fed Coal Stove:**Hitzer 983 insert**Baseburners & Antiques:**Glenwood #8**Coal Size/Type:**Coal Contractors Mammoth nut, Direnzo nut, Lehigh stove**Other Heating:**45 year old oil furnace,and a crappy 22 year old heat pump

Keepaeyeonit wrote:Larry,there is no way in hell I could run over 100 or 120 LB's in 24 hrs or the stove would be 750 or 800*.The coldest day this year I used just a bit over 73# in 24 Hrs for the 3 coldest days with the stove running about 610 to 625*.I don't know about the BTU ratings for the stoves(at a 100% efficiency I would need to burn over 190# a day to get 100,000 BTUs so in my opinion theres no way for the 983 to run that high) but I think its BS,all I know is that it heats the house pretty dam good so if I am missing something please tell me .Keepaeyeonit

I think all coal stoves that come with BTU ratings to begin with are grossly overrated with regard to BTU's, and particularly so for the hand fired varieties, but on top of this your stove was the largest exception to the rule of all of those for which my simple formula was attempted in that it did not fit my initial formula well at all. So lets go back to your actual manufacturers rating for the stove. The manufacturer said yours was 100,000 BTU as I recall. Half of that is 50,000 BTU, and to achieve that you would need to burn 4.1 lbs. per hour or 98 lbs. per day. Your stove works absolutely great and this is just an exercise, so don't lose much sleep over it.

I'm now beginning to wonder if cutting the BTU ratings in half even does them justice. Perhaps that is still too conservative a cut-back. Any hourly rate of consumption that exceeds 700 degrees on the surface of the stove seems excessive as well as unsafe.

Last edited by lsayre on Sun Jan 19, 2014 7:33 am, edited 1 time in total.

- lsayre
**Stoker Coal Boiler:**AHS S130 Coal Gun**Coal Size/Type:**Blaschak Anthracite Pea**Other Heating:**Resistance Boiler (13.5 KW)

lsayre wrote:31,500 output BTU's / 0.75 (for 75% efficiency) = 42,000 input BTU's (half of the full rated 84,000)

42,000 BTU's/Hr. / 12,150 BTU's/Lb. = 3.46 lbs. per hour

24 hours x 3.46 lbs./Hr. = 83 lbs.

If burning 2.5 lbs/Hr. gives you 525 surface degrees, what would 3.46 Lbs./Hr. be giving you in the same stove (if combustion efficiency remains the same)? That's 38.4% more coal being burned per hour. I would surmise that the extra 38.4% would have the stove hovering around 700 degrees.

yep, i agree with those #'s and the idea that it would likely take 700*+ to burn that weight of fuel per hr.

you can get there from alot of diff. directions. 57,750 - 25% inefficiency = 43,312, pretty close to the half mark.

- KingCoal
**Hand Fed Coal Stove:**1- Warm Morning # 617A, 3-Locke Warm Morning #120, 1-Locke Warm Morning #524B**Baseburners & Antiques:**2014 DTS C17 Base Burner**Coal Size/Type:**Nut Anth.**Other Heating:**none

To get to 700 from 500 you would have to burn over twice as much fuel.

http://mb-soft.com/public3/woodstov.html

The example in the above link is assuming a 10 sq. ft. stove with air temps at 72F

The hotter you get the stove the faster it sheds heat and it goes up fast the farther you get the stove temp above the room temp.

http://mb-soft.com/public3/woodstov.html

The example in the above link is assuming a 10 sq. ft. stove with air temps at 72F

The hotter you get the stove the faster it sheds heat and it goes up fast the farther you get the stove temp above the room temp.

- ddahlgren
**Hand Fed Coal Stove:**Crane 404

ddahlgren wrote:To get to 700 from 500 you would have to burn over twice as much fuel.

http://mb-soft.com/public3/woodstov.html

The example in the above link is assuming a 10 sq. ft. stove with air temps at 72F

The hotter you get the stove the faster it sheds heat and it goes up fast the farther you get the stove temp above the room temp.

Thanks! Then it seems that for most stoves the BTU/Hr. outputs calculated by multiplying 140 x Sq-Ft of firebox ID should be just about right for a decent safe upper maximum limit of burn rate. You can of course exceed safe limits at your choosing. Warped grates, doors, etc... are then on you.

But another part of the problem to consider is that stove surface temps are not well distributed. To get an overall 700 degree surface temp you might be at 900+ in some spots.

- lsayre
**Stoker Coal Boiler:**AHS S130 Coal Gun**Coal Size/Type:**Blaschak Anthracite Pea**Other Heating:**Resistance Boiler (13.5 KW)

The purely empirically calculated maximum safe burn rates for the stoves we have looked at (which fit the initial formula in this thread) then become:

DS Machine model 1627 = 6.7 lbs./Hr, or 161 lbs/day

Glenwood 208 cook stove = 1.62 lbs.Hr, or 39 lbs./day

Crane 404 = 2.1 lbs./Hr, or 50 lbs./day

Crawford #40 = 1.75 lbs./Hr, or 42 lbs./day

Glenwood #6 = 3.1 lbs./Hr, or 75 lbs./day

Glenwood #8 = 3.93 lbs/Hr., or 94 lbs./day

Many old stoves with 111 in their name = 1.47 lbs./Hr, or 35 lbs./day

Many old stoves with 114 in their name = 2.37 lbs./Hr, or 57 lbs./day

Many old stoves with 116 in their name = 3.1 lbs./Hr, or 75 lbs./day

Many old stoves with 118 in their name = 3.93 lbs/Hr., or 94 lbs./day

Harman Mark III = 4.42 lbs./Hr, or 106 lbs./day

DS Machine model DS-1400 = 3.46 lbs./Hr., or 83 lbs./day

Harman SF260 = 5.43 lbs./Hr., or 130 lbs./day

American Standard Severn = 5.83 lbs./Hr., or 140 lbs./day

Clayton 1537G = 5.81 lbs./Hr, or 140 lbs/day (mid-ranging this one here)

Compare these figures to your maximum daily anthracite burn rate for the absolutely coldest one or two days of the coldest years and let me know if these figures seem close. Of course, you shouldn't have to hit these limits, so hopefully you haven't actually achieved or exceeded them (too often at least). if you are more than occasionally exceeding these limits, perhaps your stove is undersized for the task.

DS Machine model 1627 = 6.7 lbs./Hr, or 161 lbs/day

Glenwood 208 cook stove = 1.62 lbs.Hr, or 39 lbs./day

Crane 404 = 2.1 lbs./Hr, or 50 lbs./day

Crawford #40 = 1.75 lbs./Hr, or 42 lbs./day

Glenwood #6 = 3.1 lbs./Hr, or 75 lbs./day

Glenwood #8 = 3.93 lbs/Hr., or 94 lbs./day

Many old stoves with 111 in their name = 1.47 lbs./Hr, or 35 lbs./day

Many old stoves with 114 in their name = 2.37 lbs./Hr, or 57 lbs./day

Many old stoves with 116 in their name = 3.1 lbs./Hr, or 75 lbs./day

Many old stoves with 118 in their name = 3.93 lbs/Hr., or 94 lbs./day

Harman Mark III = 4.42 lbs./Hr, or 106 lbs./day

DS Machine model DS-1400 = 3.46 lbs./Hr., or 83 lbs./day

Harman SF260 = 5.43 lbs./Hr., or 130 lbs./day

American Standard Severn = 5.83 lbs./Hr., or 140 lbs./day

Clayton 1537G = 5.81 lbs./Hr, or 140 lbs/day (mid-ranging this one here)

Compare these figures to your maximum daily anthracite burn rate for the absolutely coldest one or two days of the coldest years and let me know if these figures seem close. Of course, you shouldn't have to hit these limits, so hopefully you haven't actually achieved or exceeded them (too often at least). if you are more than occasionally exceeding these limits, perhaps your stove is undersized for the task.

- lsayre
**Stoker Coal Boiler:**AHS S130 Coal Gun**Coal Size/Type:**Blaschak Anthracite Pea**Other Heating:**Resistance Boiler (13.5 KW)

And in actual use, that Glenwood 208 cook stove goes through 30 pounds a day, average.

And up to about 34 pounds, when it's down well below zero all day and night.

Even with the fire box now removed of clinker scale and back to 7 inch wide, it's not going through anymore coal.

If I burned up 39 pounds in 24 hours, I'm pretty sure the support plate over the center of the firebox would be glowing bright red the entire time and warped after that.

Paul

And up to about 34 pounds, when it's down well below zero all day and night.

Even with the fire box now removed of clinker scale and back to 7 inch wide, it's not going through anymore coal.

If I burned up 39 pounds in 24 hours, I'm pretty sure the support plate over the center of the firebox would be glowing bright red the entire time and warped after that.

Paul

- Sunny Boy
**Hand Fed Coal Boiler:**Anthracite Industrial, domestic hot water heater**Baseburners & Antiques:**Glenwood range 208, # 6 base heater, 2 Modern Oak 118.**Coal Size/Type:**Nuts !**Other Heating:**Oil &electric plenum furnace

Sunny Boy wrote:And in actual use, that Glenwood 208 cook stove goes through 30 pounds a day, average.

And up to about 34 pounds, when it's down well below zero all day and night.

Even with the fire box now removed of clinker scale and back to 7 inch wide, it's not going through anymore coal.

If I burned up 39 pounds in 24 hours, I'm pretty sure the support plate over the center of the firebox would be glowing bright red the entire time and warped after that.

Paul

Perhaps you can do it now that your firebox is back to full size? Either way, these upper consumption limits should not be tested very often, if at all.

- lsayre
**Stoker Coal Boiler:**AHS S130 Coal Gun**Coal Size/Type:**Blaschak Anthracite Pea**Other Heating:**Resistance Boiler (13.5 KW)

lsayre wrote:Sunny Boy wrote:And in actual use, that Glenwood 208 cook stove goes through 30 pounds a day, average.

And up to about 34 pounds, when it's down well below zero all day and night.

Even with the fire box now removed of clinker scale and back to 7 inch wide, it's not going through anymore coal.

If I burned up 39 pounds in 24 hours, I'm pretty sure the support plate over the center of the firebox would be glowing bright red the entire time and warped after that.

Paul

Perhaps you can do it now that your firebox is back to full size? Either way, these upper consumption limits should not be tested very often, if at all.

Yes, going by how well it's reacting and how hot it can get now, it very possibly could. But like you say, I'm not risking warping parts for a rare stove just to find out.

Since the de-scaling, the firebox is putting out much more heat. At times almost too much. And since sealing the many small air leaks, it responds quicker to damper changes. I now have the opposite problem - trying to keep it slowed down when I don't need high cooking/baking temps! I've had to reduce the primary damper openings for both day and night use.

Paul

- Sunny Boy
**Hand Fed Coal Boiler:**Anthracite Industrial, domestic hot water heater**Baseburners & Antiques:**Glenwood range 208, # 6 base heater, 2 Modern Oak 118.**Coal Size/Type:**Nuts !**Other Heating:**Oil &electric plenum furnace

Anyone know the length and width (inside of firebrick to inside of firebrick) for the Keystoker HFH-90 hand fired stoves firebox?

- lsayre
**Stoker Coal Boiler:**AHS S130 Coal Gun**Coal Size/Type:**Blaschak Anthracite Pea**Other Heating:**Resistance Boiler (13.5 KW)

Sunny Boy wrote:lsayre wrote:

Perhaps you can do it now that your firebox is back to full size? Either way, these upper consumption limits should not be tested very often, if at all.

Yes, going by how well it's reacting and how hot it can get now, it very possibly could. But like you say, I'm not risking warping parts for a rare stove just to find out.

Since the de-scaling, the firebox is putting out much more heat. At times almost too much. And since sealing the many small air leaks, it responds quicker to damper changes. I now have the opposite problem - trying to keep it slowed down when I don't need high cooking/baking temps! I've had to reduce the primary damper openings for both day and night use.

Paul

Let me revise that.

Woke to -2 yesterday and it only got up to 4 for the high. Woke to -22 this morning and by 10 am it was only up to -13 in the shade. This has been the coldest it's been since I got the stove. I've now put 1-1/2 buckets of coal through it in the last 24 hours. Each bucket holds about 32 pounds of nut coal. The stove is cranking out heat.

Draft is so strong at these low temps that to slow it down, the primary damper and the MPD are hardly open. Even at that, the firebox end top plates have been averaging in the mid 700's.

Luckily, haven't needed to use the check damper to keep the top plates from glowing red, . . . yet.

Paul

- Sunny Boy
**Hand Fed Coal Boiler:**Anthracite Industrial, domestic hot water heater**Baseburners & Antiques:**Glenwood range 208, # 6 base heater, 2 Modern Oak 118.**Coal Size/Type:**Nuts !**Other Heating:**Oil &electric plenum furnace

lsayre wrote:Disclaimer: Please do not attempt taking measurements while stove is hot!

Dammit!! Why do you always have to ruin everyone's fun?

I believe my fire box is 16" w X 20" d.

- I'm On Fire
**Hand Fed Coal Stove:**DS Machines DS-1600 Hot Air Circulator

I'm On Fire wrote:lsayre wrote:Disclaimer: Please do not attempt taking measurements while stove is hot!

Dammit!! Why do you always have to ruin everyone's fun?

I believe my fire box is 16" w X 20" d.

Based on 16 x 20 x 375 that would be 120,000 BTU's

But based on 16 x 20 x 140 that would be a max safe 44,800 BTU's per hour of output, or about an input max of 118 lbs. of coal per day. Have you ever hit or exceeded 118 lbs. burned in a single day?

- lsayre
**Stoker Coal Boiler:**AHS S130 Coal Gun**Coal Size/Type:**Blaschak Anthracite Pea**Other Heating:**Resistance Boiler (13.5 KW)

lsayre wrote:

Based on 16 x 20 x 375 that would be 120,000 BTU's

But based on 16 x 20 x 140 that would be a max safe 44,800 BTU's per hour of output, or about an input max of 118 lbs. of coal per day. Have you ever hit or exceeded 118 lbs. burned in a single day?

The most I've burned in a single day was maybe 80 pounds. So no, I've never burned through 118 pounds of coal.

- I'm On Fire
**Hand Fed Coal Stove:**DS Machines DS-1600 Hot Air Circulator

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