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Post by peterberg on Dec 6, 2013 2:28:02 GMT -8
So i should make it smaller then? I remember when we spoke you told me that the safe area is 5,5 to 6 sq/meter... is that right? Yes, you are right, but this remark has been made when we spoke about a 6" batch box rocket. That's an entirely different beast, output is way higher in terms of kW/h. And yes, of course there's a limit to the size of a stove. Otherwise, the chimney will stay cold and condensation will inevitably stall the system rather sooner than later. All this rocket systems are heavily depending on high gas velocity so it's important to maintain strong draft. Yes, the surface of the column (not every brick's total surface!) will be added to the ISA of the stove. And no, you won't feel the radiation of the column through the wall of the bell. Nevertheless it's there, it will store heat and contribute to the heat storage capacity of the stove. A steel beam inside the stove will expand, so you have to give it room at the ends in order to keep your stove together. Line the ends with superwool, providing a slip and expansion joint. When the oven is directly above the riser you have to place it on a refractory slab, this will spread the heat. Otherwise your pizza's will be cremated instead of baked. Since the top of the oven is higher up in the bell it will heat up all around, no problem.
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Post by Robert on Dec 6, 2013 3:28:38 GMT -8
So what ISA would be safe for the 6inch j-tube than?
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Post by peterberg on Dec 6, 2013 5:05:55 GMT -8
I would estimate 4 m² as adequate. Dependent on the quality of the chimney that is, no hard numbers are available.
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Post by Robert on Dec 12, 2013 6:58:52 GMT -8
Hmmm 4m.... thats kind of very limiting i would say... But also maybe it can solve the "problem" with attaching the oven... i will have to redesign it than again...
actually there will be no "normal" chimney... since there is no one in the house... i am planning just to use the regular (160 cm) stove pipe and stick it out the wall... is that a big change for the ISA?
and also what do you think about the desired lenght of the pipe?
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Post by peterberg on Dec 12, 2013 9:46:04 GMT -8
Hmmm... A chimney pipe through the wal and then up isn't an adequate chimney at all. Actually, the entire stove pipe should be indoors up to the roof and should stick outside about 50 cm above the highest point. Everything which is outside has to be insulated, and when possible also the rest of it inside the house envelope as well. Otherwise the stove will perform very poorly, sorry.
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Post by Robert on Dec 12, 2013 13:47:51 GMT -8
Oh. The famous chimney issue. As we were told many places that Rockets don`t need chimneys we (which i mainly mean me) tends to think this way that the chimney is not needed. I remember we spoke about that things and of course i did`nt understand all of the subject. As now i understood that the chimney should be quite tall, insulated and the temp of the flues should be quite high to avoid condensation issues. So i was thinking this way that: 1. There will be quite high insulated pipe inside the house, about 3 meters long.. 2. Then it will go through the wall and go outside for another 1m high ( i am not sure if it will go higher then the top of the roof)... i am going to use the double insulated chimney which i am posting on an image below. All together it will be 4 m, so should be enough dont you think? And they use a lot of this kind of the chimney here that are being placed outside the house... What i found out is that usually people use them for gas burners, which has lower temp. on the exit... So how do you think should it work? And here are the pictures:
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Post by peterberg on Dec 13, 2013 5:19:43 GMT -8
The 3 meter inside the house is the most important, that 1 meter outside won't cause a cold plug that easily. When the end of the chimney pipe isn't higher than the top of the roof you'll find out sooner or later that could cause trouble in very specific circumstances. Like down wind over the top of the house. Double walled and insulated is a lot better than bare pipe so you're on the right track.
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Post by Robert on Dec 14, 2013 12:51:20 GMT -8
Thanks. The double insulated chimneys are quite expensive, but i will explain all of it to the client. I am just wondering. So i will ask. Since i have seen that the stove you have build on the workshop doesn`t not have a long chimney at all, and it sticks out the wall... Just as i would like to do mine. How this one is working? How long chimney is outside the wall? I can see it is a batchbox so it also makes a difference?
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Post by peterberg on Dec 14, 2013 13:16:53 GMT -8
OK then, inside is 1.75 meter of bare pipe, outside is 2.5 meter of double walled insulated stainless steel chimney. All together it's just above the highest point of the roof. It's built in an old stable, we were not allowed to puncture the roof and we used mainly second hand materials which were at hand. We tried to run it with just the pipe through the wall and we were smoked out. Once the chimney was connected, the thing was very reluctant to start. But after a while it warmed up and it formed a cosy place to spend the evening and having beer.
The core itself is a batch box, in fact the first one made from refractory castable. The exit temperature happened to be about 140 Celsius, the cob shell of 4 cm thickness became hot enough to burn one's hand. The plan is to fatten up the cob shell to 10 cm.
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Dec 14, 2013 13:57:55 GMT -8
The exit temperature happened to be about 140 Celsius, the cob shell of 4 cm thickness became hot enough to burn one's hand. The plan is to fatten up the cob shell to 10 cm. Peter, is there a standard point where exit temperature readings should be taken? My exit temperatures are the same as above, measured as the stainless pipe exits the mass wall.
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Post by peterberg on Dec 15, 2013 0:42:27 GMT -8
Depends on the stove construction, I would say. In my case, there's a bare stove pipe exiting at floor level, which turn vertical immediatly after. For convenience, I do measure at a height between 1 and 2 meter (3 and 7 ft) from the floor. Other stoves may have a top vent, in that case it's best to measure directly after the chimney damper.
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Dec 15, 2013 1:09:28 GMT -8
Thanks Peter. I'll use the access panel @ approx. 1 metre.
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Post by Robert on Jan 10, 2014 12:36:07 GMT -8
Hello dear friends. As i work on few projects as the same time i had a little break from this one. Now catching up slowly, and coming more towards the actual design. I Made few changes. But still need some of your precious support. Thats how it looks for now: So as they say problems become a solution. While i had to make the ISA of the stove smaller, the problem of supporting the oven has solved by it self. I will use the bricks in this way: And for closing the bell. We have nice "chamotte" plates here 1000cm/500cm/3cm which fits wonderfully. What do you think are they strong enough to use the one piece, or better split them and use two pieces? Eventually i want to build an arch over them for keeping the dishes warm, for the client (the husband who comes later from work and wants his wife to place the dish in the shelf to keep it warm for two, thre hours) I also change the place for the tube, but that in the next episode
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Post by Robert on Mar 31, 2014 10:03:23 GMT -8
Ok Guys. So i am coming back to this project. Thanx to your advices now i think i have final version ready to be designed and build soon. Its going to be a J-Tube with the air provided from outside. So i have one question. If my system is 18cm, what size of the tube for the air from outside should be? Do you think that 10cm will be enough? And this is how the design looks today:
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Post by pyrophile on Apr 4, 2014 14:07:47 GMT -8
I made such a stove in but with concrete blocks, protected by -first- thin (5cm)concrete blocks for the first half of the height then by regular bricks (on the edge). I will try again to show pictures but I do not succeed... This 20 cm (8'') system was maybe 180 high, 180cm large and maybe 60cm in depht. Inside this bell I added a vertical labyrinthe (chicane in french) made with bricks on edge, making the travel for gases longer. The bricks of the J rocket were lightweight bricks. I put insulation beetween the stove and the wall. Incoming air came from inside the house. The oven was simple : 2 refractory bars above the heat riser, a bit on the right set in the bricks on edge (which protected the concrete blocks).
I can send images to somebody (Satamax, are you around here?) who might put them here ?!!
Benoit
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