I took out the 30 gal barrel stove I had been using and replaced it with a 55 gal. After lining the inside with firebrick I used sewer grating as the fire grate - about 200+ lbs. I tested it yesterday. I admit that the outside temp was much warmer than usual, but inside a half hour, with 3 very small fans distributing the air, I got an air temp of 100+ F in an extremely leaky and uninsulated section of the barn . Better yet, after I cooled the place down by opening the door and letting the fire die, 3 hours latter I still had 70 F. Even better, I used less wood than I would have in the 30 gal.