Old topic revisited: How does a stove get its BTU rating?

Old topic revisited: How does a stove get its BTU rating?

PostBy: lsayre On: Thu Sep 19, 2013 9:42 am

This has been discussed here many times over the years, but none of the answers I've seen in the past completely close the issue regarding just how the various manufacturers come up with a BTU rating for their hand fired stoves, Does grate size matter? Firebox size? Surface area? Flue diameter? Magic? Science? Whim? VooDoo? Etc...?

Therefore, I'm opening this to new discussion on the hope that perhaps some new insight into this matter will come forth.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Anthracite Pea
Other Heating: Resistance Boiler (It has been fixed!)

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: freetown fred On: Thu Sep 19, 2013 10:00 am

I guess I hate to say this---NO I DON'T-- :clap: Being a wood burner for 30 yrs. or more, when I made the switch to coal--I looked for ONE thing---STRUCTURAL SOUNDNESS-- there are other stoves out there equivalent in performance, but I ended up with my HITZER 50-93--she is solid plate steel, hopper fed ( many power outages here on the hill), blower available & as simplistic as this old farmer was looking for kinda stove--it was a common sense( seemingly a dying art in this day & age) choice on my part--I seriously think that there is a fine line between thoughtful research & mind-fcking one's self. I believe that in boilers/furnaces there is a lot more to be looked into compared to hand-fired. As far as BTU ratings??????? they are what they are---my own rating system comes down to--and I've said this time & again-- when I first lit off the HITZER---she heated the house nicely = good BTU rating---if she had not = bad BTU rating. Again, this is posted in the Hand Fired Topic section & that's all I'm speaking on--I have had 5 uneventful burning seasons thanx to the help I've gotten on this FORUM & will be forever grateful for that. :D
freetown fred
 
Hand Fed Coal Stove: HITZER 50-93
Coal Size/Type: BLASCHAK Nut/Stove mix

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: Rigar On: Thu Sep 19, 2013 10:30 am

I'm with FF........ there is definitely a science to it all !!:)

.... I cannot speak for all manufacturers... but with most heating appliances the BTU rating: is usually an input (usage of fuel) at maximum load...
propane, natural gas, heating oil,.. have extremely consistent quantities of BTU's per gallon/lb...
and the higher the efficiency ... the more output they will have ( obviously)

... with coal ( and these are just numbers I can remember)... you could potentially have a 2000 to 4000 BTU differance per pound of fuel....
.....even a 1500 btu deficit per lb is 3 MILLION BTU per ton
... so to answer your question... I don't have a clue as to how manufacturers of coal burning appliances can actually guarantee a BTU input / output rating.... other than a mean average based on a tested coal supply...( which would have to be tested to determine its actual BTU output per pound)

... just my 2 cents
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

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Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: franco b On: Thu Sep 19, 2013 11:00 am

The European stoves are tested at government laboratories and the outputs are about half what a comparable size US built stove is rated at. Of course the US importer promptly doubles the output in his literature.

I believe most US stoves receive their Btu rating during UL testing when the stove is fired as hard and hot as they can make it burn. It's a rating achieved by badly over firing the stove. Cut it in half for a more real world figure. Just calculate how many pounds of coal it would take to achieve those crazy output figures. Efficiency would also be very low because of high stack temperatures at those firing rates. Until standards are set you can only go by the relative size of the stove just as the antiques went by the fire pot size.
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: Old topic revisited: How does a stove get its BTU rating?

PostBy: Rigar On: Thu Sep 19, 2013 11:09 am

good point Franco...

MY keystoker claims 160,000 btu per hour OUTPUT !.
...thats a shitload of coal per hr now that you mention it
... I'm heating well over 3000 square feet... solely with coal (4000) when you consider the basement)
when it is below zero outside... and windy...(and running alot) ...i go thru about 75 lbs TOPS in 24 hrs... so granted it is cycling on and off... I burn maybe 3 pounds per hour... hell... let's say 4

... we don't keep it hot in the house... 70.... but it is 70 everywhere...
I would have to burn over 10 pounds per hour to get there BTU rating???
.. hmmm
maybe they are mistaken about the stove performance?
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: freetown fred On: Thu Sep 19, 2013 11:18 am

Come on Rigar--they're sales people :clap: toothy
freetown fred
 
Hand Fed Coal Stove: HITZER 50-93
Coal Size/Type: BLASCHAK Nut/Stove mix

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: Rigar On: Thu Sep 19, 2013 11:27 am

freetown fred wrote:Come on Rigar--they're sales people :clap: toothy




...True...
but what I was getting at was my furnace doesn't fire full-l out all the time
.. I have my feed rate 15 to 17 turns out usually
13 on the coldest days
....if it ran at max load (feed) at a constant rate...it would have more realistic INPUT of 250,000 btu or more...???

... either way Fred... I'm with you,
keeps the house warm (and her happy)... so it has a good BTU rating no matter how ya slice it !!!
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: Rigar On: Thu Sep 19, 2013 11:34 am

...maybe i will put exactly 200 lbs of coal in the hopper....and just let the stoker run at full feed (not burning)....and time how long it takes to empty the hopper...
would that be a fair assessment of input?
...actually i do recall it will push unburnt coal into the ashpan if allowed to fire non stop at 9+10 turns out... I think I will just leave it alone.... :lol:
Rigar
 
Hot Air Coal Stoker Furnace: Keystoker A 150
Coal Size/Type: anthracite rice
Stove/Furnace Make: Keystoker
Stove/Furnace Model: A 150 warm air furnace

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: Lightning On: Thu Sep 19, 2013 1:43 pm

Call l stove manufacturer and ask them. :D

Other than that, I think You would have to do your own based on fuel consumption.
Lightning
 
Hand Fed Coal Furnace: Clayton 1537G
Coal Size/Type: Nut/Stove Size Mix

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: lsayre On: Thu Sep 19, 2013 4:09 pm

For input BTU's (which I agree are what is most likely being advertized), and allowing that carefully lab dried anthracite averages about 13,200 BTU's per pound:

1 Lb./Hr. = 13,200 BTU/Hr. = 24 lbs/day
2 lbs./Hr. = 26,400 BTU/Hr. = 48 lbs./day
3 lbs./Hr. = 39,600 BTU/Hr. = 72 lbs./day
4 lbs./Hr. = 52,800 BTU/Hr. = 96 lbs./day
5 lbs./Hr. = 66,000 BTU/Hr. = 120 lbs./day
6 lbs./Hr. = 79,200 BTU/Hr. = 144 lbs./day
7 lbs./Hr. = 92,400 BTU/Hr. = 168 lbs./day (Keystoker's HFH-90 roughly fits here)
7.5 lbs./Hr. = 99,000 BTU/Hr. = 180 lbs./day (Hitzer 50-93 and Alaska Kodiak and DS-1500 roughly fit here)

I would have to agree with franco b's assessment that the European stove ratings (which are about half of our ratings) may be closer to the overall truth.

For hand fired stoves multiply the above BTU/Hr. figures by about 0.65 to see a fair first guesstimate of output BTU's. Stokers may go as high as 0.80 times the above for output.
Last edited by lsayre on Thu Sep 19, 2013 6:10 pm, edited 1 time in total.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Anthracite Pea
Other Heating: Resistance Boiler (It has been fixed!)

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: lsayre On: Thu Sep 19, 2013 4:47 pm

I came across this post which states that for DS Machine, their BTU rating is roughly 400 BTU's for every square inch of burn. Does that mean grate surface area or firebox surface area (or something else)?

BTU output question
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Anthracite Pea
Other Heating: Resistance Boiler (It has been fixed!)

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: McGiever On: Thu Sep 19, 2013 4:56 pm

lsayre wrote:I came across this post which states that for DS Machine, their BTU rating is roughly 400 BTU's for every square inch of burn. Does that mean grate surface area or firebox surface area (or something else)?l


Now we need to call DS Machine to see if 400 btu was factored w/ Harmony or Stockton's coal...holy mackrel :|
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: lsayre On: Thu Sep 19, 2013 5:22 pm

McGiever wrote:Now we need to call DS Machine to see if 400 btu was factored w/ Harmony or Stockton's coal...holy mackrel :|


I believe that's why Coalfire specified that Amos at DS Machine told him it was "roughly 400 BTU's".
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Anthracite Pea
Other Heating: Resistance Boiler (It has been fixed!)

Re: Old topic revisited: How does a stove get its BTU rating?

PostBy: franco b On: Thu Sep 19, 2013 5:29 pm

lsayre wrote:I came across this post which states that for DS Machine, their BTU rating is roughly 400 BTU's for every square inch of burn. Does that mean grate surface area or firebox surface area (or something else)?

BTU output question

Has to mean grate surface area. 400 times 144 equals 57,600 Btu for a one foot square grate burning at the rate of about 6 pounds per hour or 144 pounds for 24 hours. Good luck doing it.

What a stove can produce in theory is a lot different in practice. That's how you get absurdities like a Chubby producing 70,000 Btu.
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: Old topic revisited: How does a stove get its BTU rating?

PostBy: lsayre On: Thu Sep 19, 2013 5:35 pm

DS Machine lists their firebox dimensions as follows:

DS-1500 = 16" x16"
DS-1600 = 16" x 20"

16 x 16 x 400 = 102,400 (and the DS-1500 is rated at 96,000 BTU's)
16 x 20 x 400 = 128,000 (and the DS-1600 is rated at 120,000 BTU's)

This probably means they are using the grate area, which would be a bit less than the firebox area. I wonder how well this simple grate area formula works for other hand fired stoves?

edit/update: If you use 375 BTU's per square inch of firebox cross sectional surface area, then the DS Machine BTU ratings are right on the money.
Last edited by lsayre on Thu Sep 19, 2013 5:50 pm, edited 1 time in total.
lsayre
 
Stoker Coal Boiler: AHS S130 Coal Gun
Coal Size/Type: Anthracite Pea
Other Heating: Resistance Boiler (It has been fixed!)

Visit Hitzer Stoves