Hello dose anyone know how they determine BTU's for a wood stove my stove a Monark add a furnace is stamped 48000 btu , the fire box was over heated when the fan motor failed last year. I used it a few times this year and had smoke in the house. I have found a stove ( Norseman 2500 ) that is rated at 115000 btu's but is SMALLER in size then mine?? I am scared that it will be to much for my system, (my wood stove is out side and the air is moved through 10 inch duct work under the ground ) but shouldn't I be able to control the output by controling the draft ?? It would be nice to have it going as it is about 10 below as I am righting this. Thanks Bryan