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Post by willowways2 on Jan 21, 2012 23:26:37 GMT -8
so as the title says i have moved from a single to a double wall heating duct for my RSMH. now i need to cut the heat riser to get that 2" gap. i was thinking of filling the space with ash. however ash when mixed with moisture creates lye, so what is a good alternative for a small gap of a double wall heating duct.
i figured if i use ash or sawdust they both become ash and create lye. not sure if i can get vermiculite or perlite in a small enough grain to fit in a little over a 1/2 cm space. i could try a refractory foam that's fire resistance if i could find one located in Colorado.
any ideas?
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hpmer
Full Member
Posts: 240
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Post by hpmer on Jan 22, 2012 3:41:12 GMT -8
What's your hesitation with ash? I've had good success with ash mixed with clay slip to help keep the ash from compacting. Takes a while to dry, but seems to hold up pretty well. I used the mixture to build my entire heat riser. Use gloves when mixing as it can be a bit rough on the skin.
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Post by pasto76 on Jan 22, 2012 7:51:51 GMT -8
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Post by willowways2 on Jan 22, 2012 9:59:49 GMT -8
i am using it to fill in a space of about 1/2 cm of a double walled heating duct. mid you that's two walls of metal and and when ash creates lye it becomes corrosive to metals. such as the heating duct work.
was there a ratio of clay slip to ash?, also what was the thickness of the ash-clay slip compound?
thank you pasto that should be helpful.
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Post by canyon on Jan 22, 2012 10:41:03 GMT -8
Masonry grade perlite is super fine and will go in your gap. If I understand you correct, you are using double wall (type B) vent pipe for your heat riser? That is such a small amount of insulation and the thin wall of that stuff will burn out in a short duration. If you are wanting to use metal for the riser, better to find thicker wall pipe unless you are only using it for a form. But maybe you have some kind of odd thick double wall that I am not familiar with?  |
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Post by pasto76 on Jan 22, 2012 13:40:42 GMT -8
now that donkey mentions it, one of the reasons I moved from a barrel stove to a RMH is that the inner wall of the Type B duct would melt if I had more than a small fire going. The gauge on that inner wall is pretty damn thin.
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