What size corn burner
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When sizing your corn burner there are several things to consider and many variables.
- how well insulated is the home?
- Number of floors?
- Does the house have a basement?
- How much energy in BTU's (a universal constant) are they using with their current system.
- Freestanding unit or furnace?
- Is corn easily available where the stove will be installed
Planning to Install Stove in the Basement? The www.iburncorn.com forum presents many stories of disappointment from people who have installed a corn or pellet stove in an otherwise largely unheated basement in hopes that it would heat the upstairs. They commonly forget that the stove must be sized to heat both the upstairs and the basement. So for a 1700 sq. ft. single story bungalow, the stove would need to be able to heat 3400 sq. ft., not just 1700 sq. ft. This can be a tall order especially if the basement walls are not insulated. While successful basement installations have been reported, it is generally agreed that installation directly in the living space gives the greatest likelihood of success.
Heat Loss Use this to calculate heat loss; http://www.pprbd.org/plancheck/Heat%20Loss%20Table.pdf
No matter what you do, when it is 68° F inside your house, and 0 degrees outside your house; the cold will suck the heat out of your house. It will pull at a certain rate through the exposed walls and ceilings, through the windows and floors. This is known as heat transfer.
The cold air is also trying to sneak into the building through every little crack in every nook and cranny. This is known as infiltration. Your heat, on the other hand, is trying to escape through every nook and cranny. This is known as exhilation.
The total of all this leaking and losing at a specific low temperature for your region, is known as the heat loss. This total will be calculated in btu's per hour, and the heating system will need to produce and distribute this same amount of btu's per hour to maintaint your 68° F room temperature. As most rooms differ from one another, each room's heat loss must be determined. The total loss of all rooms added together will determine the size and design of the heating system.
In the heat loss calculation, all windows are created equal, no matter which direction they face. Disallowing for wind factors, similar types of glazings lose heat at the same rate. On the other hand, when calculating heat gain, windows facing east and west gain more heat that those facing north and south. This results in larger quantities of air being distributed to rooms with east and west facing windows.
How many BTUs your old system is rated at is not generally a good starting point. Many things may have changed since that system was originally sized. The house may have undergone changes. Rooms may have been added, windows replace, insulation added. Perhaps the furnace is not even burning the original fuel it was designed for and rated with. All of these factors change how you will compute the required size of your stove before even taking into account any extra heating load your new corn stove would require if you install it in an otherwise unheated basement, as discussed above.
"The old fashioned way was to measure the outside wall area, window and door areas, ceiling and floors. There are heat loss charts for all those areas with different values for insulation thickness, number of and type of windows, doors, wall types, etc.. Then the climate where you live is a factor, what the worst wind speed and lowest temperature for your location is a factor. You crank all the information together and come up with the BTU output size of the heating device you need. An allowance is added for a safety factor on the chance that unusual extra cold weather occurs. It really isn't too complicated. If you could post the tables and values and show an example, that would do it."
Sellers of corn burners will quote lots of numbers for BTU/lb of corn. Sometimes even up to 10,000 BTU/lb. But, 6800 btu/lb is more realistic.
Here is something that is important. BTU ratings on stoves and furnaces are INPUT BTUs! That means if you put 19 pounds of corn in per hour, at 6800 BTU/lb, you would have 130,000 BTU furnace.
BUT, don't forget that if your stove runs at 80% efficiency, which is quite good for a corn burner, the actual btus into the room or water (if its a boiler) would be 104,000 BTUs.
(6800 X .80)
At $3/bu for cost of corn production, that turns out to be about $9 per million btus. Still not to shabby compared to oil $2.25/gal or $18.22/mbtu ($15.84 at 85% eff.) and natural gas at $1.60/therm or $17.60/mbtu ($16 at 90% eff.) of course you should add a delivery fee to the corn, but it still looks pretty good.even at $3.50/bu