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Post by pigfarmer on Jan 30, 2015 12:10:23 GMT -8
Now I have a new purpose in mind for the bricks my wife's been using for flowerbed borders I'll have to replace them with rocks witch we have a ton of around here on the farm. I've been working on a 6"j box rmh for the greenhouse I am adding on the south side of our barn but now since finding this forum the other day I'm convinced a Peterberg batch stove is a more practical solution. I wonder if the 3 ' section of double wall insulated stainless steel chimney pipe i was planning on using for a heat riser will (a) provide enough temperature differential to make the heater work properly and (b) last very long due to the high temps involved. I started building my rmh last winter after seeing you tube videos about them. I'm using an old bladder style water tank for the heat exchanger over the heat riser that the bladder went bad in .I cut it apart and took the bladder and associated guts out then welded it back together. I was thinking of using cement blocks dual purpose for exhaust for the stove and heat storage , I wonder if this would work very well? They would be sitting on some 2"thick steel insulated garage door panels I have laying around to isolate the blocks from the ground then I was going to build a frame around it filled with dirt for a heat sink /grow bed. I wonder if the porous nature of the blocks core would create too much drag for the exhaust to flow through, also how much length I can get away with running the exhaust thru both cores of 16"cement blocks then into a vertical 6" b'vent chimney. Any advice/experience anyone would be willing to share I would greatly appreciate !
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Post by pigfarmer on Jan 30, 2015 12:41:57 GMT -8
The greenhouse I'm putting together is 16'x 28' on the south side of our barn. Its covered with poly-carbonate glazing and an assortment of thermal pane windows and door walls. I'm planning on using polyurethane on the inside of the framing for an additional insulation bubble. I'm going to have passive solar heat storage in black poly drums filled with water and I could possibly incorporate a coil in the heat exchanger to thermal siphon /heat water from the drums. I don't know if that's practical or if it would work.
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Post by peterberg on Jan 30, 2015 13:03:39 GMT -8
Don't use stainless for the riser, it will fail in a season. Even heavy gauge will fail in two or three years. The steel won't melt but it will corrode like grazy because of an oxygen-rich and carbon-lean environment coupled to high temps.
Pig, since you want an answer to a lot of questions, it would be better to start a new thread and ask your questions there. As an alternative, I can do it for you and replace your posts, what title would be OK?
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Post by pigfarmer on Jan 30, 2015 13:12:17 GMT -8
Just one more thing, I want to say a huge thank you to Peterberg and all the forum members for all your ideas and effort and willingness to share your wealth of experience so freely ! I have been heating with wood my entire life and have built several central heat systems incorporating barrel stoves, thermal mass and ducting as an auxiliary heat source for forced air heat systems with great success. This new technology is a quantum leap over what I have used in the past so I'm really excited to see how well its going to work and how much less wood it will use.
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Post by pigfarmer on Jan 30, 2015 13:46:54 GMT -8
Thanks Peterberg that would be great. Maybe call it rocket mass batch heater in a greenhouse ? Thanks for the info on the stainless chimney pipe . In your experience how long will fire bricks last? I'm planning a 6" batch stove with the "s"tube configuration. Just as an aside I had a soapstone woodstove that had stainless steel pipes for secondary combustion air in the top of the burn chamber. Hearthstone used this technology to get epa certification on their stoves back in the early 1990's.
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Post by peterberg on Jan 30, 2015 14:10:46 GMT -8
Hard firebricks are sold in different heat specs. Normally you'll get 2370 F or 1300 C, that would be adequate for 15 to 20 years. Depending on how hard you drive the stove of course.
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Post by DCish on Jan 31, 2015 7:04:58 GMT -8
Just as an aside I had a soapstone woodstove that had stainless steel pipes for secondary combustion air in the top of the burn chamber. Hearthstone used this technology to get epa certification on their stoves back in the early 1990's. I have one of these now, nice stove for a standard box. The reason they can get away with using metal in the combustion zone is that their burn temps are so much lower. Imagine fully loading up that Hearthstone, then letting it burn through the entire load if wood with the side door open for the whole time. You would seriously wreck so many parts of that stove! Yet this burn regime is what a batch box is designed to do every time, hence requiring more robust refractory materials.
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Post by pigfarmer on Feb 1, 2015 11:49:56 GMT -8
I used that stove for 10 years burning 24/7 approx 180 days / yr here in Michigan before it fell apart . The stainless steel secondary tubes eventually degraded to the point that they fell out and I replaced the stove with a Harmon top loader that I have now. It was cool to watch the co burning blue above the fire around the tubes and the air flowing through them probably contributed to them lasting as they did.
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Post by pigfarmer on Feb 1, 2015 14:37:13 GMT -8
That experience leads me to believe that the tubes should be made in such a way so that they can easily be replaced. Being a Toolmaker with 40 yrs experience I can think of a few ways to achieve this. If you are using the square tube "s" tube design. Cut holes in the secondary air feed tube that passes under the fire box the same size as your vertical tubes in the same place where you would have welded the vertical tubes in place. Then add collars welded onto the vertical tubes just far enough from the lower end to keep the tube in place when standing vertically then you would need a frame around the tubes welded at the bottom to the sides of the secondary feed tube (with a cross bar tying the sides together at the top) as tall as the tubes with holes in the top cross bar to accept the top of the vertical tubes. Then when the vertical air tubes degrade and need to be replaced just lift them up and tip them toward the center to remove them so that they can be easily replaced. You would have to leave enough room in your masonry construction for clearance at the top to facilitate lifting and tipping the tubes for removal and replacing.
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Post by DCish on Feb 2, 2015 13:03:31 GMT -8
Along the lines of "replaceable" I thi k Matt Walker's thread on converting a J tube to a batch box is a good way to go. A single "L" shaped tube on its back that can slide in and out easily. Maybe recess the back wall a bit so it gets close in the port so as to not obstruct loading length.
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gjh42
Junior Member
Posts: 61
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Post by gjh42 on Feb 3, 2015 23:05:48 GMT -8
Yes, I think the walker pre-port tube is probably the best way to go for easy replaceability as well as maximum efficiency. It's more exposed to damage from wood, but more exposed to inspection too.
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