Questioning BTUH Calc

A Coal stoker furnace or stove controls most operations including automatically feeding the coal. They are quite similar to any conventional oil and gas units and easily operated for extended periods of time. They commonly use rice coal but may use larger sizes like buckwheat. They can be used as primary heat, supplementary heat or have a dual set up with your existing oil/gas furnace.
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mooseman100
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Stoker Coal Boiler: EFM 520
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Location: winchester, va

Post Tue. Mar. 08, 2011 8:41 pm

I used info online from mrhvac.com. It was pretty detailed, asked about sq ft of outside wall, and roof, type of doors and window as well as thier proximty to the sun. It came out just a hair under 100,000 required. What seems odd to me is that I am heating nearly 5,000 sq ft of home with alot of tall ceilings. My trophy room alone is 1,200 sq ft with 14' tall ceilings. There are other tall ceilings in the house as well. It is a newer home with proper insulation and I live in Winchester, VA, 2 hrs south of Harrisburg, pa. Does this sound light to you guys?

I currently am heated with 2 zones of heat pump with LP back up, I think each unit is a 2 1/2 ton unit.

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Rob R.
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Location: Chazy, NY

Post Tue. Mar. 08, 2011 8:48 pm

I am not surprised at the 100k BTU figure. What did you use for design temperatures?

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Flyer5
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Post Tue. Mar. 08, 2011 8:51 pm

I can believe that for your climate , it sounds to be close.
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mooseman100
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Post Tue. Mar. 08, 2011 9:12 pm

I used 70 degree inside and 20 degree outside. So maybe a KA-6 would do it and not the KB-8. It will be in an outside shed does that add much into the calculation?

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Rick 386
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Post Tue. Mar. 08, 2011 11:06 pm

mooseman100 wrote:I used 70 degree inside and 20 degree outside. So maybe a KA-6 would do it and not the KB-8. It will be in an outside shed does that add much into the calculation?
You just have to plumb it correctly to get that 100 k inside the house. How long a run, what size pipe, etc.

Rick
Master of "Trial and Error."

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Sting
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Other Heating: OBSO Lennox Pulse "Air Scorcher" burning NG
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Post Tue. Mar. 08, 2011 11:15 pm

mooseman100 wrote:I used 70 degree inside and 20 degree outside.
ummmmm --- so your targeting a 50 degree temperature rise on the dwelling

because ......

It never gets colder than 20 in your back yard

I am moving there.
When you turn your boiler on -Does it return the favor?
I have finally lost my mind. Don't bother to return it. It wasn't working properly anyway!


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Richard S.
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Post Tue. Mar. 08, 2011 11:51 pm

mooseman100 wrote: It is a newer home with proper insulation and I live
That's a big factor , how thick are the walls? If they are 6 inch I could really believe it.
"The difference between stupidity and genius is that genius has its limits."

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Sting
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Post Wed. Mar. 09, 2011 8:13 am

http://lwf.ncdc.noaa.gov/oa/climate/online/ccd/meantemp.html

The mean temperature (average) for January of the last 30 years in Roanoak VA is 35.8

In Green Bay its 15.6

Now we all know it get colder than 15 in Green Bay and the same holds true in VA -- So my point is if your design temperature rise is only 50 degrees - when it the weather will turn cold and you have evenings below zero - you WILL need a second source of energy to add power to the system. An oil or propane backup or dual fuel will not fail over and help pick up the load. While I recommend under-sizing the solid fuel appliance as you have - because it will operate more of the time at its peek efficiency - you will need some sort of primary/secondary or series boiler configuration where they both can run. And they may both have to run as much as 100 hours a season, with this low a calculation.

Now that written -- if your using a negative 20 not positive 20 and calculating your design load up from 40 degrees colder -

Thats a nice house! 8-)
When you turn your boiler on -Does it return the favor?
I have finally lost my mind. Don't bother to return it. It wasn't working properly anyway!

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steamup
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Location: Napoli, NY

Post Wed. Mar. 09, 2011 8:34 am

20 btuh/sq ft is reasonable for a very well insulated newer house. However, do not cut yourself too tight with solid fuel device sizing, as they are slower to respond.

ASHRAE Weather Data indicates at the 97.5% design dry-bulb is 10 deg. f. for Winchester. This means on the average, the temperature is at or above this temperature 97.5% of the time. If you use this temperaure without a safety factor, your heating system will struggle 2.5% of the time on average.

I would re-run the calc using 10 deg. f. Make sure you have a safety factor in the calculation for pickup, piping losses and unforseen such as extreme weather conditions. For an outside shed and piping to the structure, I would add and additional 15 to 20% above this number. The shed will be toasty warm.

I would not go less than a K-6 and might consider a K-8 for that amount of sq ft. Consider the K-8 if you want to indirectly heat your Domestic water also. With that large of a house, you must have several bathrooms.

Be careful in planing the piping between the shed and house. You will need more than one single pair of 1" lines.
Steamup

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