I agree that the Osburn is not what it claims to be. I purchased one 3 years ago to help heat my 4,000 ft2 shop. I keep the hydronic floor on to 48 degrees and raise the heat with wood when working. Bought the Osburn 2400 with fan to replace a Vogelzang ( spelling) box stove that was using too much wood. The Osburn is rated by themselves at 78% efficiency and 100,000 btu, it's rated by the US EPA at around 63% efficiency and around 44,000 btu. My guess is somewhere between the two.
The good news is, it seemed to burn better( hotter) after a month or so, maybe the moisture in the refractory being evaporated. While it does not put out heat like the Vogelzang, it is much safer to run and burns about 1/2 the wood, I still run it 3/4 to all the way open, with 3 year seasoned oak, and an additional fan behind the unit. It brings my shop temp from 48 to 60 in 2 to 3 hours and up to 65 by the end of a 8 hour day.
I am slowly starting to like the unit but would not buy another.
Good luck to you
The good news is, it seemed to burn better( hotter) after a month or so, maybe the moisture in the refractory being evaporated. While it does not put out heat like the Vogelzang, it is much safer to run and burns about 1/2 the wood, I still run it 3/4 to all the way open, with 3 year seasoned oak, and an additional fan behind the unit. It brings my shop temp from 48 to 60 in 2 to 3 hours and up to 65 by the end of a 8 hour day.
I am slowly starting to like the unit but would not buy another.
Good luck to you