Boiler Heating Surface Area in Sq-Ft Vs. Gross Output BTUH
- lsayre
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I believe that for residential size anthracite stoker boilers you can get a decent initial ballpark guess of their Gross BTUH output rating if you know their heating surface area in square feet, by multiplying the heating surface area in square feet by 7,500. Does this sound like a good first guess?
Gross Output BTUH = 7,500 x Heating Area in Sq-Ft
Then from there, to get Net (pick-up factor adjusted) BTUH, divide Gross BTUH by 1.15 for hot water use, or divide by 1.33 for steam.
Then for most boilers a fair initial compromise (guess) of the Input BTUH rating would come from dividing Gross Output BTUH by 0.75
The boilers estimated max feed rate can then be ballparked via:
Max Feed Rate (Lbs.) = Input BTUH/12,300
This might come in handy for the case where an older stoker boilers sq-ft of heating surface is known or can be measured, and where no other information is known for it.
Gross Output BTUH = 7,500 x Heating Area in Sq-Ft
Then from there, to get Net (pick-up factor adjusted) BTUH, divide Gross BTUH by 1.15 for hot water use, or divide by 1.33 for steam.
Then for most boilers a fair initial compromise (guess) of the Input BTUH rating would come from dividing Gross Output BTUH by 0.75
The boilers estimated max feed rate can then be ballparked via:
Max Feed Rate (Lbs.) = Input BTUH/12,300
This might come in handy for the case where an older stoker boilers sq-ft of heating surface is known or can be measured, and where no other information is known for it.
- StokerDon
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This is interesting Larry. I intend to measure the inside surface on my BairMatic boiler just so I could compare it to other boilers. I have no idea what the net or gross output of the original BairMatic was. I could take this thing for a test drive since I know the heating surface area of my Van Wert VA600.
Gross Output BTUH = 7,500 x 24.5 Sq-Ft = 183,750
Then from there, to get Net (pick-up factor adjusted) BTUH, divide 183,750 by 1.15 for hot water = 159,782.6 divided by 0.75 = 213,043 BTUH?
The boilers estimated max feed rate can then be ballparked via:
Max Feed Rate (Lbs.) = 213,043 BTUH/12,300 =17.32 pounds per hour.
Not to bad Larry. The VA600 fires at 18 pounds per hour according to the Van Wert manual!
-Don
Gross Output BTUH = 7,500 x 24.5 Sq-Ft = 183,750
Then from there, to get Net (pick-up factor adjusted) BTUH, divide 183,750 by 1.15 for hot water = 159,782.6 divided by 0.75 = 213,043 BTUH?
The boilers estimated max feed rate can then be ballparked via:
Max Feed Rate (Lbs.) = 213,043 BTUH/12,300 =17.32 pounds per hour.
Not to bad Larry. The VA600 fires at 18 pounds per hour according to the Van Wert manual!
-Don
- lsayre
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Thanks Don! Looks like it ballparked the Van Wert VA600 pretty close. Should be useful for your BairMatic.
But upon further inspection, Input BTUH is derived from the Gross, so 183,750/0.75 = 245,000 Input BTUH
And 245,000/12,300 = 19.9 lbs./hour max feed rate
Still close, but perhaps not as close as your way.
But upon further inspection, Input BTUH is derived from the Gross, so 183,750/0.75 = 245,000 Input BTUH
And 245,000/12,300 = 19.9 lbs./hour max feed rate
Still close, but perhaps not as close as your way.
Last edited by lsayre on Wed. Oct. 26, 2016 8:04 pm, edited 1 time in total.
- Scottscoaled
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Jeeze Larry! You are making my EFM 520 with 28 square feet a real weiner
28 x 7500 divided by 1.15 divided by .75 = 243,478 BTU's of real coal burnin, butt heating power!!!!!!
Also giving me a feed rate of 19.8 lbs per hour. That would be in line with a ten tooth feed rate of buck or a 8 tooth feed rate of rice.
28 x 7500 divided by 1.15 divided by .75 = 243,478 BTU's of real coal burnin, butt heating power!!!!!!
Also giving me a feed rate of 19.8 lbs per hour. That would be in line with a ten tooth feed rate of buck or a 8 tooth feed rate of rice.
- lsayre
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28.3 sq-ft last time I checked. A serious heat monster. I could heat 3 to perhaps 4 homes like mine with a single boiler if I had an EFM DF520. Call it 3 homes plus DHW.Scottscoaled wrote:Jeeze Larry! You are making my EFM 520 with 28 square feet a real weiner
28.3 x 7500 = 212,250 Gross Output BTUH
212,250/0.75 = 283,000 Input BTUH
283,000/12,300 = 23.00 lbs./hour max feed rate
Last edited by lsayre on Wed. Oct. 26, 2016 8:16 pm, edited 1 time in total.
- Scottscoaled
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28 square feet last time I checked
- lsayre
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28.3 sq-ft is what they currently indicate on their website. Perhaps they didn't have room to stamp it 28.3? Or they've more recently expanded them a tad? Close enough either way.
- Scottscoaled
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Pretty tag isn't it?
- lsayre
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Looks like my ballpark method should get you within about +/-10% of factory rated actual figures. That should be close enough for most purposes.
Last edited by lsayre on Wed. Oct. 26, 2016 8:28 pm, edited 1 time in total.
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I think you're both right about the heating surface. I believe round door plate boilers were 28.3. Square doors are a little less due to door size (and maybe the oil port). Of course, if you want real heat exchange efficiency you could always consider the 30.8 sf of one of the earlier tube boilers...
Mike
Mike
- lsayre
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You must spit shine it daily to keep it that nice.Scottscoaled wrote:Pretty tag isn't it?
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Larry, I think the method may break down if you have a mfgr like Leisure Line who achieves high efficiency by matching (AA) boiler heads with less stoker power than the heads are rated for. The computations aren't going to increase the actual throughput of the stoker(s).
Mike
Mike
- lsayre
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It would be interesting to see if it ballparks to within 10% of the rated figures for the LL boilers.Pacowy wrote:Larry, I think the method may break down if you have a mfgr like Leisure Line who achieves high efficiency by matching (AA) boiler heads with less stoker power than the heads are rated for. The computations aren't going to increase the actual throughput of the stoker(s).
Mike
- Rob R.
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oooo, ahhhhh.
Looking good scott. I have insulation over mine.
Looking good scott. I have insulation over mine.
Agreed, it is the total design that counts, not just once piece.Pacowy wrote:Larry, I think the method may break down if you have a mfgr like Leisure Line who achieves high efficiency by matching (AA) boiler heads with less stoker power than the heads are rated for. The computations aren't going to increase the actual throughput of the stoker(s).
Mike
- lsayre
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So far it seems to be within 10% for the likes of the AA-260, AHS S130, AA-130, Van Wert 600, and EFM DF520. That's not bad for a simple, down and dirty "ballpark" method. Ballpark methods are never intended to be perfect.