Doc,
I agree with you I have run long distances on the submersible stock heaters I purchased from Nasco and had no problems,just use a very heavy outdoor extension cord,number 10 or 8 just my .02 worth,I am speaking strictly for myself.Any connections etc,tape them and keep everything away from a house or barn in case of a malfunction.
But you have peaked my curiosity about the heaters that are kept going with firewood. Where have you seen them or who makes them ? I like to read about alternative stuff like that.
Thanks
Old_Hickory