Have a harman coal stoker that is vented into a 40' 6" flexible ss liner. I have magnetic stove thermometer in the stove and a probe thermometer inserted in the flu pipe about 2 feet away from the stove.The stove is connected to the ss liner by 8" of stove pipe off the stove then the barometeric dampner then a 90 Degree elbow then 4 feet of stove pipe.i've noticed with the barometric dampner closed the flue temp is around 100 degrees less then the stove temp.If i fully open the barometric dampner i can lower the temp of the flue by almost 100 degrees but the stove temp doesn't increase.I thought as th dampner opens and takes in room air the stove should get hotter cause your not sending all that heat up the flue..Is my thinking flawed yet once again...lol