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Oh, No! Smoke-back! Heat riser gap question

 
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This is my second year with my rsmh. I rebuilt it this year, it's better than last year, but i still get some flame-ups and such out the feed tube. i am wondering if this is 1) normal. and 2) possibly due to the space between the heat riser and barrel, which is currently at three inches. My current is setup is as follows:
Feed tube is 4.5" x 7"
Burn tunnel is 6 x 7 by 12 inches long
Heat riser is 8 x 36 inch round ceramic pipe which is insulated
with an inch and a half gap between it and the outer barrel
Exit area is 8 inch stove pipe as well as a secondary 6 inch stovepipe.

this setup is just not as rockety as i would like to see, and i get the occasional issues as i mentioned above.
Tips? Tricks? Words of wisdom..or perhaps a magic spell?
Honestly any and all thoughts and ideas are appreciated.

Thanks!!
 
Posts: 69
Location: Susquehanna, PA
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How deep is your feed tube? Is the 4.5x7 the sides? If so, your feed tube CSA is only 31.5 but your burn tunnel's CSA is 42 (6x7) and your heat riser CSA is 50.24 (8in pipe area), that's a problem. It sounds like your CSA (cross section area) needs to be examined throughout and more consistent. Yes, 3in gap atop your heat riser seems like a bit much. A 2in gap better matches the airflow of an 8in pipe, I wouldn't want anything under 1.5" to maintain good airflow. My $.02
 
eric lane
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thanks for the two cents! you think if i increased my feed tube to 6x7" it would help the draw? i am curious...i thought usually many people increase their draw by making the opening of their feed area smaller. i dont know, but i am eager to learn!
 
Martin Seidel
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Location: Susquehanna, PA
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