If you're heating your house on 'exclusively' 4 tons of anthracite per year...

... and you are wondering how to size a heating appliance such as a furnace or boiler to your house, then you might be wondering how many BTUH does 'Manual J' indicate your house requires?

Lets see:

4 tons x 2,000 lbs/ton x 12,300 BTU's/lb. = 98,400,000 BTU's (Note: this figure can be derived for any fuel, and not just coal)

Presumption #1: Your present appliance is 80% efficient

0.80 x 98,400,000 = 78,720,000 BTU's required to be "delivered" (or output) whereby to heat your house annually.

Presumption #2: Your area sees 6,200 annual HDD's

78,720,000/6,200 = 12,697 BTU's per HDD

12,697/24 = 529 BTU's per hour per HDD

Presumption #3: Your locations Manual J "Design" temperature is 5 degrees F.
Presumption #4: You intend to keep your house at 72 degrees during the winter

72-5 = 67

67 x 529 = 35,443 BTUH

Per 'Manual J' a heating appliance capable of outputting 35,443 BTUH will heat your home to 72 degrees F. for 99% of the "average" year.

Per a 'Manual J' "rule of thumb" you should size your appliance 40% larger than this if you want to keep your house at 72 degrees on the coldest single day likely to occur once every 10 years.

Therefore: 35,443 x 1.4 = 49,620 BTUH output is the correct size heating appliance for your house.

If the heating appliance is 80% efficient, then it should be rated for an input of 49,620/0.80 = 62,025 BTUH (call it 62,000)

62,000 BTUH input should work well for sizing a furnace.

But for boilers, to account for what is referred to as boiler "gross/net" (or the "pick-up factor"), multiply this by 1.15.

1.15 x 62,000 = 71,300 input BTUH for a boiler.

NOTE: A 95%-96% efficiency condensing furnace or boiler will only be about 84% efficient on the coldest days of the year. It will not be condensing under such conditions.

Larry, you're sick....you need help LOL! Although I don't fully understand most of your posts, thank the lord we have you and for the help with this stuff you have provided me in the past and I hope you stick around to see me succeed (hopefully) with my new installation.

swyman wrote: ↑

Fri. Oct. 09, 2020 7:39 am

Larry, you're sick....you need help LOL! Although I don't fully understand most of your posts, thank the lord we have you and for the help with this stuff you have provided me in the past and I hope you stick around to see me succeed (hopefully) with my new installation.

Actually it is the people who have been heating their home on 4 tons of coal or less per year and who subsequently decide that it likely requires on the order of a 130,000 BTUH (or larger) furnace or boiler who are sick. And I'm merely trying to make them well.

Sooooo, those calculations would be true to my 200 yr. old broke up farm house that is insulated as well as a post & beam structure can be?

freetown fred wrote: ↑

Fri. Oct. 09, 2020 7:50 am

Sooooo, those calculations would be true to my 200 yr. old broke up farm house that is insulated as well as a post & beam structure can be?

Yes - the size of age of the structure makes no difference if you are starting with a known amount of fuel consumption. By doing it this way, you are already allowing for the heat load of the house and the typical weather in your area.

The things you need to watch out for is assuming that the historical fuel consumption resulted in a comfortable interior temperature. This is more of a concern when trying to size a coal stove based on how much heating oil or propane someone used in the past. If they kept the house at 60 degrees on propane and expect it to be 80 with the coal stove, that needs to be accounted for.

What Rob said!

Fred, figure on ~7,050 HDD's for Cortland proper. And more if you are at greater elevation. Add up to ~1,000 additional HDD's if you are way up there in the hills. (I don't know how hilly it is there, or how high those hills can be with respect to Cortland). The "Design" temperature for Cortland is zero degrees F.. If you're way up in the hills use -2 degrees for the "design" temperature to be safe.

And this,Boys and Girls,is why this Place Rocks! Imagine a First Timer stumbling into here! They'd be expecting to encounter a Pack of Drooling,Knuckle-Dragging Druids in here,burning Da' Black Rocks! Then they encounter Our Merry Band of Genius's.... Whoo-Whee! Surprise!!
Thanx,Larry!!(And All Other Elevated Thinkers And Do'ers!!

Another way to approach it is from the perspective of the coldest possible anticipated temperature (sticking with my example above). The coldest I've ever seen here in my lifetime is minus 22 degrees F.

Therefore:

On a day when it is minus 22 degrees F. outside (that means -22 degrees F. actual, and not via wind chill), and you want it to be 72 degrees F. inside:

72 - -22 = 94 HDD's experienced on that day

94 HDD's x 529 BTU's/HDD/Hour = 49,726 BTUH output required.

On the single coldest day when it was -22 degrees outside here I burned ~105-110 lbs. of coal. Call it 110 Lbs.

110 lbs. x 12,300 BTU's/lb.x 0.80 eff. /24 hours in a day = 45,100 BTUH output required
(where BTUH means 'BTU's per hour')

The lowest actual temperature ever recorded here was minus 26 degrees F. That temperature comes around once every roughly 200 years here.

What scares me most is I understand it now it took until last year with some back and forth with Larry to get it but I do. The thing with it is its a real good guideline and not a one size fits all because of actual temps and other variants. If it looks like you need 4 ton with this formula buy 5 tons in case its a cold winter. Actually buy 6 tons and turn the temperature up because 72 is kinda chilly

But even though I understand it I still do it the same as Fred likely does and I dont worry about it. I just make sure I have enough fuel for a cold winter. New home owners, especially a large home, could benefit from using the formula or they could just buy a trailer load of coal and find out that way.

My neighbor has a very well insulated 3000sqft brick ranch and wants to buy my LL boiler and put it in his basement. I was a little reluctant but I'm 2400 2 story plus garage and barn 200' away. I think it would work very well for his application but again I am no expert. I would HATE for it not to be able to do the job.

Your neighbor should call LL and ask for their input.

swyman wrote: ↑

Fri. Oct. 09, 2020 9:51 am

My neighbor has a very well insulated 3000sqft brick ranch and wants to buy my LL boiler and put it in his basement. I was a little reluctant but I'm 2400 2 story plus garage and barn 200' away. I think it would work very well for his application but again I am no expert. I would HATE for it not to be able to do the job.

How much fuel is he using now?

Your local HDD's (Heating Degree Days) are easily found here. You want the annual figure:

https://www.huduser.gov/portal/resources/UtilityM ... l/hdd.html

or here:

https://www.melissa.com/v2/lookups/zipclimate/zipcode/

Your local Manual J "Design Temperature" is found here (where it is called "Winter Heating 99% Dry Bulb"):

https://farm-energy.extension.org/wp-content/uplo ... ns_508.pdf