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Post by Solomon on Dec 13, 2020 16:19:20 GMT -8
I'm in the process of building an 8 inch J tube "standard" cob style RMH (as constructed by Erica and Ernie) in my home. I want to start with this in order to get a feel for how it works, and maybe it will be exactly what I'm looking for.
However, I grew up with wood stoves, and I really like the idea of a batch box, and the idea of burning larger loads at once, and also seeing the fire.
And just looking at options, somebody claimed that a 6" batch box would produce about double the heat of an 8 inch J tube (30 something kW vs 14 kW). What about an 8" batch box?
Would it be inadvisable to use the same 8 inch piped mass and chimney for a 6 inch batch box?
Could there be an issue with too much heat produced by an 8 inch batch box?
I have a pretty big house, two story ~3800 SF, 2x4 walls and a little leaky at this point, though I plan to work on that over time as well. RMH is going to be more or less in the middle of the first floor on slab floor.
I also want to experiment with water mass storage as well, but that's a project for another time. Water stores a lot more heat per mass than stone. And can also be piped to distant locations.
Some personal background, I'm educated as a civil engineer, a competent welder, and reasonably skilled home plumber and electrician.
Thanks for any answers you have and ideas also.
Solomon
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Post by Dan (Upstate NY, USA) on Dec 13, 2020 16:38:19 GMT -8
I built an 8" j tube that I have had for 7 years. Had to rebuild this fall due to the ceiling bricks being shot.
But I could have went for a 6" system and have been fine.
Woke up this morning and the house was 69F, burned one 5 gallon bucket of wood to get the ceiling up to 76, the rest of the house stabilized to 71 by noon.
If I had a 6" system I would have had to burn half the bucket and reload and do a second burn.
You decide, either or will work.
Do you have a chimney already, what size is it?
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Post by Solomon on Dec 13, 2020 20:31:34 GMT -8
Do you have a chimney already, what size is it? 8 inch chimney, straight up, about 20 feet of insulated pipe, from ceiling to cap. Goes through a second floor bathroom corner. It was part of the bathroom remodel, have to finish the bathroom first.
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Post by martyn on Dec 14, 2020 0:44:55 GMT -8
There are a few different styles of batchbox , Peters original batchbox is very well documented and tested, for out and out fast burning performance it is hard to beat! if you enjoy looking at the fire there is also the shoe box designs and the vortex stove .
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Post by Solomon on Dec 15, 2020 8:40:50 GMT -8
Still looking for thoughts on the following questions:
Somebody claimed that a 6" batch box would produce about double the heat of an 8 inch J tube (30 something kW vs 14 kW). What about an 8" batch box?
Would it be inadvisable to use the same 8 inch piped mass and chimney for a 6 inch batch box?
Could there be an issue with too much heat produced by an 8 inch batch box?
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Post by josephcrawley on Dec 15, 2020 10:54:08 GMT -8
Still looking for thoughts on the following questions: Somebody claimed that a 6" batch box would produce about double the heat of an 8 inch J tube (30 something kW vs 14 kW). What about an 8" batch box? Would it be inadvisable to use the same 8 inch piped mass and chimney for a 6 inch batch box? Could there be an issue with too much heat produced by an 8 inch batch box? If you compare the volume of fire in a J to a batch box you will see there is quite a substantial difference between the two. So yes it would be a reasonable claim. An 8 inch will produce a heck of a lot more than a 6. The firebox is huge in comparison. I would not recommend using piped mass with a batch box especially if you went with an 8 inch system. It may be okay with a 6 if you use 8 inch pipe throughout. If you haven't built the mass yet don't use the pipe at all and build an open bell system. With the size of your house I think an 8 inch system would be a better fit than a 6.
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Post by Solomon on Dec 15, 2020 14:33:50 GMT -8
I would not recommend using piped mass with a batch box especially if you went with an 8 inch system. It may be okay with a 6 if you use 8 inch pipe throughout. If you haven't built the mass yet don't use the pipe at all and build an open bell system. Can you talk more about this? Are you concerned about the flow of an 8" batch box going through an 8 inch piped mass? Mass not big enough to absorb enough heat? What about the 8" that Peter Van den Berg built in Paul Wheaton's shop? That uses an 8 inch piped pebble mass. By an open bell system, are you talking about a much bigger masonry style machine? Or an open bench style?
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Post by josephcrawley on Dec 15, 2020 15:04:59 GMT -8
I would not recommend using piped mass with a batch box especially if you went with an 8 inch system. It may be okay with a 6 if you use 8 inch pipe throughout. If you haven't built the mass yet don't use the pipe at all and build an open bell system. Can you talk more about this? Are you concerned about the flow of an 8" batch box going through an 8 inch piped mass? Mass not big enough to absorb enough heat? What about the 8" that Peter Van den Berg built in Paul Wheaton's shop? That uses an 8 inch piped pebble mass. By an open bell system, are you talking about a much bigger masonry style machine? Or an open bench style? Are you talking a deadend bench or one were the heat passes through the bench on the way to the chimney? There is a lot more drag in an 8 inch pipe versus an open bench. By open I mean something with a large passage surrounded by mass on the top and sides.
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Post by Solomon on Dec 15, 2020 17:22:09 GMT -8
Are you talking a deadend bench or one were the heat passes through the bench on the way to the chimney? There is a lot more drag in an 8 inch pipe versus an open bench. By open I mean something with a large passage surrounded by mass on the top and sides. I'm talking about getting as much heat out and having a bullet proof system, that's why I'm starting with a bog standard 8" J rocket. What I'm wondering about is if it can be later converted to a 6 or 8 inch batch box. Are you meaning a large brick style bell? I've seen many design possibilities but few with such detailed instructions and history of operation as Erica and Ernie's J rockets. I would really like to play with batch boxes in the future. I like the 8 because of standard sized wood but I'm concerned if it can be adapted and how much heat it will put out. Maybe I could mitigate some the instantaneous heat output with water storage. I do have a slightly limited bench space, certainly not the 40 feet allowed. I have about 9x9. A possible idea would be an open bench style expanded to the size of a bed. Or I could go more vertical with the mass. I was planning on an L shaped bench encompassing approximately 30 feet of pipe.
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Post by peterberg on Dec 16, 2020 1:45:02 GMT -8
What about the 8" that Peter Van den Berg built in Paul Wheaton's shop? That uses an 8 inch piped pebble mass. The heater in Paul Wheaton's shop sports two barrels on top of the firebox and one aside which was originally lined with bricks on the inside. The pebble style bench happened to be there already and I used it as such. Gases were cooled down enough by the time they reached the bench. A lot of the build's effort went into attention to making it as low-friction as possible. There's a peculiar effect with pebble benches, though. They tend to let most of the heated gases through until the temperature is above a certain threshold. Because the pebbles are touching the 8" pipe sparingly the bench will absorp heat almost exclusively by direct radiation of the pipe. A massive bench will take up heat by conduction which tend to work much more efficiently and start at a lower temperature also.
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Post by belgiangulch on Dec 16, 2020 6:35:25 GMT -8
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Post by josephcrawley on Dec 16, 2020 8:15:04 GMT -8
I'm talking about getting as much heat out and having a bullet proof system, that's why I'm starting with a bog standard 8" J rocket. What I'm wondering about is if it can be later converted to a 6 or 8 inch batch box. Are you meaning a large brick style bell? I've seen many design possibilities but few with such detailed instructions and history of operation as Erica and Ernie's J rockets. I would really like to play with batch boxes in the future. I like the 8 because of standard sized wood but I'm concerned if it can be adapted and how much heat it will put out. Maybe I could mitigate some the instantaneous heat output with water storage. I do have a slightly limited bench space, certainly not the 40 feet allowed. I have about 9x9. A possible idea would be an open bench style expanded to the size of a bed. Or I could go more vertical with the mass. I was planning on an L shaped bench encompassing approximately 30 feet of pipe. www.batchrocket.eu/images/rockets/files/Batchrocket_mass_heater_sizing.xlsxCheck out this spreadsheet and it will give you a sense of batch rocket heat output and potential sizing based on your heated volume. You certainly don't have to build the bench from brick there are excellent examples on this site of people using barrels cut top to bottom making an arch to form a more open and high surface area bench. These are then covered in cob. I would strongly recommend if you are going with the standard j tube with a long piped smoke path that you include a spot near the end to prime the flue for cold starts. It really sucks to fill your house with smoke!
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Post by Solomon on Dec 17, 2020 0:06:10 GMT -8
The heater in Paul Wheaton's shop sports two barrels on top of the firebox and one aside which was originally lined with bricks on the inside. The pebble style bench happened to be there already and I used it as such. Gases were cooled down enough by the time they reached the bench. A lot of the build's effort went into attention to making it as low-friction as possible. There's a peculiar effect with pebble benches, though. They tend to let most of the heated gases through until the temperature is above a certain threshold. Because the pebbles are touching the 8" pipe sparingly the bench will absorp heat almost exclusively by direct radiation of the pipe. A massive bench will take up heat by conduction which tend to work much more efficiently and start at a lower temperature also. I'm familiar with all the Permies builds, I've watched all the videos. The person seemed to be saying that a piped mass for an 8 inch batch box was not preferred, so I was offering the counter factual of the machine you built.
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