BTU Output Vs. Lbs of Coal, Am I Calculating This Correcly?

 
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lsayre
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Post by lsayre » Sat. Jan. 15, 2011 8:29 am

The DS-1600 is rated as a 130,000 BTU stove. I've calculated that (assuming 75% efficiency) it would require 308 lbs. of coal to achieve this output for one full day. Am I calculating this correctly?

130,000 BTU's/hour x 24 hours = 3,120,000 BTU's total (as output)

3,120,000 / 0.75 efficiency = 4,160,000 BTU's of required input

4,160,000 BTU's / 13,500 BTU's/lb. = 308 lbs. of coal input required


 
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Coalfire
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Post by Coalfire » Sat. Jan. 15, 2011 8:31 am

That would seem right

 
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tsb
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Post by tsb » Sat. Jan. 15, 2011 8:32 am

You are correct sir, but you would also have a house that is about 100 degrees.
Stoves never run flat out 24/7.

 
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lsayre
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Post by lsayre » Sat. Jan. 15, 2011 8:43 am

I'm guessing that in reality it probably requires (on average) only about 15,000 to 25,000 BTU's per hour (depending upon the outside temperature and the various parameters of the home) to heat a typical house, but this exercise brings into question just how these stove BTU ratings are derived. Perhaps they fire them up good and hot for only one hour to rate the BTU's? Or do they (meaning here all stove manufacturers) just grab BTU numbers out of thin air and apply them to their various models?
Last edited by lsayre on Sat. Jan. 15, 2011 10:27 am, edited 1 time in total.

 
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I'm On Fire
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Post by I'm On Fire » Sat. Jan. 15, 2011 10:18 am

Ds-1600 is actually rated for 125k BTU/hr. the DS-2100 is rated at 130k BTU/hr.

 
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Post by oliver power » Sat. Jan. 15, 2011 11:57 am

The DS Machine might be rated at 130,000 BTU's/Hr (guessing max rated capacity), but I doubt you'd be useing it to it's max. I couldn't imagine putting 308 pounds of coal in my stove(s) every 24 hours. My shop gets approx: 40 pounds every 24 hours idleing. House get 80 pounds every 24 hours.

 
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Post by Coalfire » Sat. Jan. 15, 2011 1:06 pm

I think these ratings are input ratings. so to achieve 130K at 13000btu per lb you would need to shovel 240lbs a day. That is a lot of coal for a home :shock:


 
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Post by CapeCoaler » Sat. Jan. 15, 2011 5:09 pm

I agree...
130k is the input rating not net output...
I have pushed 180# in 24 hrs...
Very windy and very cold...
60# every 8 hrs...

 
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Post by franco b » Sat. Jan. 15, 2011 5:17 pm

Shows how absurd some of the ratings are. Most ratings are only achievable by running the stoves at excessive temperatures, but I guess manufacturers have to keep up with their competitors claims.

Some years ago Consumer Reports tested Kerosene heaters. They set up a room with measured intake and out air and calculated output. Most were far under claims. The German Din government lab. actually does measure outputs to keep manufacturers honest. I think UL only fires the hell out of them to determine safe clearances.

 
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Post by Coalfire » Sat. Jan. 15, 2011 5:30 pm

CapeCoaler wrote:I agree...
130k is the input rating not net output...
I have pushed 180# in 24 hrs...
Very windy and very cold...
60# every 8 hrs...
What was your stove temp during this period?

 
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Post by SMITTY » Sat. Jan. 15, 2011 5:48 pm

franco b wrote:Shows how absurd some of the ratings are. Most ratings are only achievable by running the stoves at excessive temperatures, but I guess manufacturers have to keep up with their competitors claims. ........
I hear that! My Mark III is rated at 92,000 BTU's. I burn roughly 75 lbs in 24 hours. At 13,500 BTU's per pound, that's 42,188 BTU's per hour ... more in line with a Mark I. I had the Mark I, and I can tell you it wasn't enough to keep this place warm.

 
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Post by lsayre » Sat. Jan. 15, 2011 5:52 pm

CapeCoaler wrote:I agree...
130k is the input rating not net output...
I have pushed 180# in 24 hrs...
Very windy and very cold...
60# every 8 hrs...
Wow, at 75% efficiency you were yielding an average of just under 76,000 BTU's per hour of usable heat on that day. Impressive!!! It shows that the DS-1600 can output 76,000 BTU's per hour for an entire day if called upon. I'm willing to speculate that few other stoves suitable for a living room install could accomplish that feat. I would also want to know what your stove and stack temperatures looked like on that day!!!

 
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Post by dlj » Sat. Jan. 15, 2011 8:43 pm

lsayre wrote:
CapeCoaler wrote:I agree...
130k is the input rating not net output...
I have pushed 180# in 24 hrs...
Very windy and very cold...
60# every 8 hrs...
Wow, at 75% efficiency you were yielding an average of just under 76,000 BTU's per hour of usable heat on that day. Impressive!!! It shows that the DS-1600 can output 76,000 BTU's per hour for an entire day if called upon. I'm willing to speculate that few other stoves suitable for a living room install could accomplish that feat. I would also want to know what your stove and stack temperatures looked like on that day!!!

You sure got me beat. I think the most I ever pushed through my Glenwood is about 125 lbs in a 24 hour period. Stove temp was in the range of 650* to 725*F. I might be able to push more through it, just never had the need...

dj

 
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Post by CapeCoaler » Sat. Jan. 15, 2011 11:40 pm

Not sure of the temp but the dial was pegged at 5...
The thermo I had on the stove at the time was a bit off...
It said 600* but I suspect it was closer to 650* maybe higher...
It was when I first got the stove...
The baro was not dialed in and I had no MPD...
And the ash door had an alignment issue...
The wind was howling above 50 and it was maybe 6* out...
The house stayed at 72...
I will say the Mark II I had could not keep that temp in those conditions...
And the Mark was on the first floor not the basement like the DSM...

 
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Post by JBorden » Sun. Jan. 16, 2011 9:24 am

I believe the second line in the formula is wrong. You should be multiplying .75 not dividing. 3,120,000 x .75=2,340,000...you can't have a larger # than 3,120,000 if you want 75% of it.

130,000btu's/hr x 24= 3,120,000

3,120,000 x .75 efficiency= 2,340,000

2,340,000btu's/13500=173.33lbs

173.33lbs in a 24hr period= 7.22lbs per hour.

Hope my math is right. :D


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