of course it doesn't sound right. Was the furnace advertised with 3 hour burn times? This should answer your question right there. Not quite sure why you are continuing to let that furnace blow it's load right away. Take the foot off the accelerator already and install a BD. Have you even installed the manometer yet, or even temporarily checked your draft with it?? You are not going to have any different outcomes by doing nothing. This furnace is NOT being operated correctly.