The difference between a corn burning furnace and a corn burning stove is a blower. A corn stove radiates heat into the room it is in, the corn furnace is designed for Central Heating, it is designed to have the heat ducted from room to room. To this end, a corn furnace has a jacket surrounding the burning chamber and a blower which blows air over this exchanger. This air is then collected and mixed in a large sheet metal box, called a plenum, which is fabricated and installed on top of the furnace. Ducts are tapped into this box and the heated air is distributed to each room. However much air is distributed must also be brought back, this is called the return system.
The amount of air is determined by the size of the blower motor, the size of the ducts and the amount of BTU produced by the furnace. Designing a system for a corn burning furnace is the same as any fossil fuel system. A room by room heat loss, followed by a duct layout.
The benefits of a corn furnace over a corn stove, aside from complete distribution, are the accessories which can also be installed. The same accessories for any warm air type system can be used in the ducted corn burning system. This includes central air conditioning, high performance air filters, bypass humidifiers, electronic air cleaners, UV light air purifiers, etc. The secret to having this system function well is the determination of how many CFM, cubic feet per minute, of air will be flowing thru the ducts.
If the BTU input of the furnace is 100,000 BTU, and the output is 80,000 BTU, then a 1000 cfm would be a good CFM number to work with. This would allow for up to 2 ½ tons of air conditioning to be installed.
A good corn furnace has a hopper mounted alongside to automatically feed the fuel into the burn chamber. This hopper should be controlled by a thermostat, which raises or lower heat demands and correspondingly raises or lowers the amount of fuel fed into the burner.
Experience with wood furnaces has proven that cooling coils mounted on the supply or hot side of the ductwork, can be damaged by excessive heat should a power outage occur.
(A wood or corn fire keeps burning whereas a gas or oil furnace shuts off)If frequent power outages occur in your area, it might be a good idea to install the air conditioning coil on the return side of the system.