Given that used 6" duct is about 1000x as available as 8" on the freebie market, and the former has about half the CSA as the latter, could one not just run two parallel 6 inch pipes ( simple, single run, no elbows) out of the manifold and through the mass, then both outside? Would the increased surface area necessitate a slightly lessened maximum duct run? Thanks!
With essentially identical runs, you could probably make this work well. I think you would need a slightly shorter run, not because of increased surface area so much as increased friction. A smaller diameter with the same velocity (since cross section is the same) will have more friction.
You will want to recombine the runs at the end into an 8" chimney. Just dumping the exhaust outside without a chimney only works reliably in very specific circumstances, and most of the world is not going to have those constant prevailing winds that are needed.
Derick Greenly wrote:Given that used 6" duct is about 1000x as available as 8" on the freebie market, and the former has about half the CSA as the latter, could one not just run two parallel 6 inch pipes ( simple, single run, no elbows) out of the manifold and through the mass, then both outside? Would the increased surface area necessitate a slightly lessened maximum duct run? Thanks!
if you indeed have an bunch of or unlimited supply of "used 6" duct" and it is duct and not just sheet metal tubes i would say open them up at the seems where they snap together and combine two 6" ducts together to make a single 12" system or at least a single 12'' exhaust system and chimney stack if you still want to keep your 8'' system. no splitters, joiners or adapters needed, problem solved.
If you can access the split to influence relative flows so you get equalish airflow, or if you don't care about the two 6" runs putting out equal heating, then you can just split the run as you described. But if you want a longer run, the two 6" ducts combined with the splits will have distinctly more friction than an 8" run or especially a "merged" 12" duct run.
posted 2 years ago
F Styles wrote:
Derick Greenly wrote:All very chewy food for thought. But two six inch pipes have a csa around 60. Is combining into a single stack a necessity?
best thing is build a mock unit outside and test it. sounds like you have already made your decision... go for it brother.
Very astute! Head like bull.
Location: climate zone 6b
posted 2 years ago
charge ahead brother... good for you. let us know how you made out with your idea.
have you seen my NEW idea on how to build a RMH core? the proof of concept i build was just the outer part of my heat riser so i know it at least works for what i have done and very well. but i digress. The concept is like this put together standard stove pipe in your favorite RMH core shape like a J or L or whatever, then take your favorite high temp fabric like rock wool or fiberglass or other flexible porous material and soak it thoroughly into a Refractory cement slurry and do a thick paper machete like coating around the RMH heater core you created with standard stove pipe. then put a layer of flexible insulation like rock wool or such and then do another thick layer of slurry soaked high temp fabric over top of that to create your RMH core. the stove pipe will eventually burn out and leave your highly insulated hard refractory cement core in the custom shape of your choosing.