Posted by Harold Kestenholz - Hydronic Network on January 07, 2000 at 21:40:09:
In Reply to: Outside Wood vs Coal Fired Boiler posted by Neil on January 07, 2000 at 16:38:00:
The heating value of wood is 7800 to 5800 btu/lb. You plan to cut 36 cords of wood which is equivalent to moving the contents of a 20W x 25L x 8H foot garage in order to burn over 70,000 pounds of wood at less than 50% efficiency because wood burners can not be too efficient or they have small passages to clog up weekly. So 250 million btu aside from the cost of the installation will give you about 500,000 btu for each dollar.
In equivalent coal heat, you will need about 15 tons of coal for whatever price you get ($170/ton? = $2550.)
The 2500 gallon propane buy at $0.70 per gallon ($1750) gives 225 million btu that can be burned at 80% efficiency giving 180 million btu. This gives 102,000 btu per dollar, or /5 the heat value of wood.
Wood will require stoking and ash every four hours and occasional cutting. Coal will require every 8 hours (If you are perfect.) Propane will require no work. So you can cut your fuel cost by taking on the part-time job of wood cutting, cleaning and moving for 3 hours per day. 3 hrs/day x $5.50/hr x 180 days is $2970 per year at MacDonald's. You might be able to get a wife or a child to do this work aside from housekeeping, cooking, or doing homework, so you could make more money at a serious income-producing job. This should produce serious exercise into your retirement years. As a history factoid, people started using automatic heating systems 80 years ago to keep away from this work.
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