I bought the unit used from a person that moved into a new house and never used it. The unit is in good shape. So I had a professional company install it. I started a small fire the other night for 2 hours to get the new paint to cure. today I tried to start a fire and the smoke was backing up into my house. I never saw it come out the chiminey. when I closed the door it almost about choked out the fire. if I crack the door the fire grows but still dosent go up the chimney. it was about 40 degrees out. I have both primary air control and start up knobs pushed all the way in which is open. One member had a similar problem and mention that he took off a plate for air venting on the unit. if any one has any ideas, ill take them. Thanks carl