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Post by wiscojames on Feb 9, 2015 6:00:14 GMT -8
Box made with full size hard firebrick, proportions according to the spreadsheet. Two 55 gal barrels stacked. The side of the bottom cut out to accept the profile of the rear half of the firebox. (Bottom barrel at 'ground' level, not on top of firebox like Peter's Innovator's stove. The whole works will sit atop an insulated base.) The heater will exhaust through the centrally located brick chimney in out 100 year old farmhouse. The chimney is something like 10 by 16 inches.
Against all guidance to the contrary, I plan on putting this thing in my basement - because it's the only place in the house that it can possibly go. So, heat the basement workshop and maybe get some residual heat upstairs. And have backup off-grid heat if needed.
Question #1: Big mistake or potentially workable? (A) in the basement B) up a chimney of substantially bigger CSA)
I plan to add a couple inches of cob over most of the heater to soak up some heat - the fire box and maybe the entire bottom barrel, since I don't plan to add mass downstream.
Question #2: Big mistake, or potentially workable? Will I be sending lots of heat up the chimney? Should I think of a way to collect more of the heat before exiting? More mass? Fins on the flue pipe?
On one similar heater I saw (in the Netherlands, I think, and maybe built by Peter or some of his fellow Dutch stove builders) it looked like it might have been an 8" system, and the exhaust looked like it might have been 8" as well (exiting near the bottom of the bottom barrel).
Question #3: Should I be exiting with a 8"->6" reducer to increase the size of that transition? Or 6" for a 6" system? Or something else?
thanks in advance to all who ponder and respond!
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Post by peterberg on Feb 9, 2015 6:32:55 GMT -8
Question #1: Big mistake or potentially workable? (A) in the basement B) up a chimney of substantially bigger CSA) With 2 barrels coupled to the brick chimney, there's a fair chance you could get away with it. Question #2: Big mistake, or potentially workable? Will I be sending lots of heat up the chimney? Should I think of a way to collect more of the heat before exiting? More mass? Fins on the flue pipe? Potentially workable, yes. I would say: start with bare barrels, you can always cob it in after trying out, if at all. Cobbing in will mean it isn't shedding heat as much. You need quite a lot of heat to keep the chimney going but since this is inside the building the rest of the house will benefit. When there's too much heat lost, you could always take measures to harvest more. Question #3: Should I be exiting with a 8"->6" reducer to increase the size of that transition? Or 6" for a 6" system? Or something else? Starting with a larger exit is always a good thing. But why not make the whole transition to the chimney in 8"?
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Post by wiscojames on Feb 9, 2015 7:54:18 GMT -8
I was considering 8" at the barrel to 6" at the chimney only out of laziness/convenience. There is a 6" stub mortared in to the chimney from previous furnaces. I can probably make the change to an 8" stub without too much trouble - chisel a few bricks and remortar, etc.
If I leave it at 6" at the chimney am I asking for trouble, flow-wise?
Peter - thanks for your advice. Wish I could come hear your presentation at the MHA annual meeting and buy you a beer afterwards.
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Post by peterberg on Feb 9, 2015 8:41:22 GMT -8
If I leave it at 6" at the chimney am I asking for trouble, flow-wise? No, I'd think it should work as intended. The 8" inducer at the barrel side is sensible though.
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Post by wiscojames on Feb 15, 2015 19:13:38 GMT -8
Nearly ready to assemble. If I need to cut the top barrel down to better fit in the space - from 35" high to 24", say - would I be approaching a point where mass (on the bottom half of the tower maybe) should or could be added for the purpose of soaking up more heat?
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Post by peterberg on Feb 16, 2015 1:15:34 GMT -8
The barrel is shedding heat faster than the mass is able to absorb. So if you add more mass to the side of the barrel (if that is what you mean) the end temperature will rise.
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Post by wiscojames on Feb 17, 2015 6:04:53 GMT -8
Thanks for pointing that out. I understand now. Do you suppose I will be running into issues with overly hot exhaust? Should I be considering mechanisms to remove more heat? Fins on the flue? Fins on the barrel?
Thanks Peter, and all of the rest of the usual suspects, for sharing your knowledge. I feel like I might finally be able to have a positive impact on my energy usage and expenses during the winter months (which are approximately halfway through autumn until halfway through spring).
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Post by peterberg on Feb 17, 2015 8:19:31 GMT -8
Wiscojames, I haven't seen your stove, nor have I seen drawings and I dont know what quality of chimney you plan to use. The only thing you can do is try it out and report back what the results are. Cobbing the barrel will cause the end temperature to rise, that isn't a bad thing in itself. You could add another smallish barrel as a bell further downstream when that is the case, or a small mass bench or whatever. Build it and run it, see what alterations you need.
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Post by wiscojames on Feb 17, 2015 8:48:06 GMT -8
Thanks. I am in overthinking mode. I will proceed and report back with pictures and findings.
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Post by wiscojames on Feb 18, 2015 5:46:30 GMT -8
Ought I make some provision for condensation? A weep hole in some part of the flue pipe? Something to prevent the condensate from running back into the barrel or into the base of my house's chimney? Maybe overthinking again...
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Post by peterberg on Feb 18, 2015 10:30:52 GMT -8
Condensation will only occur when there's too much heat drawn from the exhaust gases, on a permanent basis. Besides that, when drying out a newly built RMH there's bound to be condensation because of the cooling effect of the whole damp mass. But that will evaporate again during the 3 or 4 weeks you need to run the thing in...
So yes, you are overthinking again.
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Post by wiscojames on Feb 25, 2015 18:33:10 GMT -8
A couple of in-progress photos. One looking down at the core and the other into the firebox. I anticipate being able to do a test firing this weekend some time.
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Post by wiscojames on Mar 7, 2015 11:47:19 GMT -8
two videos of a test burn: part 1 www.youtube.com/watch?v=I5BSbLPlBropart 2 www.youtube.com/watch?v=x9n4QdqY5V0Super draft via the ~25 feet of brick chimney. Never a whiff of smoke. Lots and lots of heat from a 1/3 or 1/2 load. Cob door with glass recycled from the outdoor project. At the height of the burn, what should the temperature be entering the brick chimney? It seemed on the high side. (Possibly approaching the 250 F service temperature of the foil tape. Given the strong draft, and seeing Satamax's most recent stove, I suspect that I might not need the foil tape at all.) If the exit temperature is higher than ideal, I was thinking of radiating fins on the barrel. I know I could make a bell or a bench downstream of the barrel, but space is at a premium, and I want to keep it as impermanent as possible.
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Post by satamax on Mar 7, 2015 12:21:36 GMT -8
Wiscojames, my experiment is just that, an experiment Mind you, i have two more barrels to burn What i can tell you, is, starting a batch rocket on the verge of stalling is a pain! It will smoke you out of the room every time! And then you need the tape!
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Post by wiscojames on Mar 7, 2015 12:47:46 GMT -8
merci, compatriote expérimentateur!
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