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Post by bulbius on May 9, 2017 10:49:51 GMT -8
Hello! I'm designing a batch box to heat an house of about 102 m2 1097 sf. The building has already the radiators system so I want to use this stove to heat primarily the water. I opted for a 8" system, do you think will it be sufficient? To heat the water I decided to put a big boiler next to the heat riser that will feed directly the water to the radiators. Also it will provide hot sanitary water by using a copper serpentine. The boiler is opened at the top. I also added a white oven directly on top of the burn box and a little cookplate over it but I'm not sure if it will reach enough high temperatures in that position. What do you think? Note, the bell that include the boiler and the oven is made entirely of insulating panels (in white) this is the s ketchup file |
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serg247
Junior Member
The mountain can not be conquered, it can allow it to ascend...
Posts: 111 
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Post by serg247 on May 9, 2017 13:04:19 GMT -8
Please save in 8 version Sketchup.
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Post by bulbius on May 9, 2017 13:58:44 GMT -8
Пожалуйста, сохраните в 8-й версии Sketchup. ok, this is version 8 |
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Post by drooster on May 10, 2017 8:33:07 GMT -8
Пожалуйста, сохраните в 8-й версии Sketchup. English, kthx. Is the jury out or in on water heating directly from rocket technology? (due to the aims and limitations of efficient secondary combustion) |
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Post by bulbius on May 10, 2017 8:51:38 GMT -8
Пожалуйста, сохраните в 8-й версии Sketchup. English, kthx. Is the jury out or in on water heating directly from rocket technology? (due to the aims and limitations of efficient secondary combustion) Drooster, the water boiler is placed after the combustion unit so it doesn't interfere with combustion efficiency |
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serg247
Junior Member
The mountain can not be conquered, it can allow it to ascend...
Posts: 111
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Post by serg247 on May 11, 2017 0:36:43 GMT -8
Пожалуйста, сохраните в 8-й версии Sketchup. English, kthx. Google translate in russian. |
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Post by bulbius on May 15, 2017 11:36:17 GMT -8
I updated the sketch adding some details about the hot water system. You can download the file here: www.dropbox.com/s/13m3hbiiexzjx33/forum.skp?dl=0This is how this thing should looks like. There is an existing fireplace on the right so I had to work out with some space restraints. Being the firebox lifted up from the floor the whole stove turns out to be raised and it almost reaches the ceiling but I think it's worth it for the comfort of putting the wood without bending.  This how the heating water system should work: Hot gases come out from the riser and enter the bell that contains the water boiler. The boiler itself is placed on the top of the bell in order to transfer most of the heat generated to the water contained therein. There are 2 tubes leaving the boiler directly connected to the radiators system; by means of a pump the hot water contained in the boiler is sent to the radiators while the cold water returns from the radiators to the boiler. The water contained in the boiler is the same as the one contained in the radiators circuit. This is an open vented system and the boiler is opened at the top with a tube to vent out the steam.  There is also a serpentine inside the boiler to generate hot sanitary water whose tubes are directed to the attic.  The primary bell is entirely made of insulating panels so that only the boiler will absorb heat, followed by the cooking plate and the oven. The total heat absorption area is about 1,5 m2 (16,14 ft2), the bell CSA is 0,47 m2 (5,05 ft2), minimum should be 0,24 m2 (2,58 ft2). |
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Post by bulbius on May 15, 2017 11:53:39 GMT -8
The oven's floor coincides with the firebox ceiling so it should became quite hot especially towards the end of the burn. It will extract some heat from the firebox which it's not so good but I'm just trying to find a compromise. The hot gases that flows in the first bell should get in contact with the top and the sides of the oven. There is a little hole (15cm x 15cm) in the bell located over the top of the oven that leads to the cooking plate, shedding heat externally. But I have some doubts that it could became hot enough to make some cups of tea.  The detail of the bell extension that should make the oven and the cooking plate hot   |
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Post by bulbius on May 15, 2017 12:04:39 GMT -8
The second bell is a bench. The gases will exit via the vertical flue that you can see in the picture. I need to find a way to lower the exit point to allow only the colder gases to leave the bench. The problem is that the condensate cap under the flue is taking much space. The orange cylinder is the water circulator (naturally outside of the smoke path) This bell ISA is 3,9 m2 (419,7 ft2), adding the first bell ISA of 1,58 m2 we get a total of 5,48 m2 (59 ft2). I read that a 8" system should have an ISA of 9,4 m2. Do you think is it worth it to add some "columns" inside the bench to increase the surface area?  |
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Post by drooster on May 16, 2017 12:55:18 GMT -8
That looks great.
Did you want to use the existing fireplace but nothing would fit?
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Post by Jura on May 16, 2017 23:05:54 GMT -8
Have you counted how many kWh (or MJ) the water volume in the system may absorb?
I can see the tank is 800x400, right?
will it be made of acid-proof stainless steel?
Make sure the water used is not "soft" so as it didn't fur up with (CaCO3, MgCo3 ).
(We used harvested rain water to fill up a buffer tank)
Project a clean out flap allowing to reach the space under the water tank.
My nose smells a flyash precipitation in there
I also can not see a shortcut (bypass) to the chimney (to allow smokeless start up of the "cold" system )
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Post by bulbius on May 17, 2017 1:30:06 GMT -8
That looks great. Did you want to use the existing fireplace but nothing would fit? No, I preferred to leave the existing fireplace intact to cook some steak  . When the BBR reach the ember phase I could take some glowing charcoals and use it inside the fireplace. |
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Post by bulbius on May 17, 2017 2:32:33 GMT -8
Have you counted how many kWh (or MJ) the water volume in the system may absorb? I can see the tank is 800x400, right? will it be made of acid-proof stainless steel? Make sure the water used is not "soft" so as it didn't fur up with (CaCO3, MgCo3 ). (We used harvested rain water to fill up a buffer tank) Project a clean out flap allowing to reach the space under the water tank. My nose smells a flyash precipitation in there I also can not see a shortcut (bypass) to the chimney (to allow smokeless start up of the "cold" system ) Unfortunately I'm not so familiar with formulas and calculations, I'm used to doing this way , so I just based my choices on my previous work where I used a similar boiler and on the space available inside the bell. I could use a smaller boiler inside the bell and put a very big water accumulator tank in the attic exploiting the natural circulation but if there is a possibility to make things simpler I like to catch it and what remains is only a boiler connected with radiators. Simple as that. In the sketch the tank is 800x400 right but it's indicative, it all depends on what I will find. In my previous project I used an old electric water boiler after removing the insulation, this wasn't stainless steel but inside was lacquered. It's almost 3 mm thick so I think it should last long. The last time I saw it looked like this: 
It was covered with a thin layer of soot (that certainly will reduce the heat transfer but it's inevitable) but no sign of corrosion. Under it you can see the pedestal with the condensate collector. During cold starts it can produce more than 1 liter (0,26 gal) of condensate! The water I'll use to fill the tank will come from a wellspring while the one I used in the other project come from a well. I will project an inspection point under the boiler and under the chimney. Also both condensate collectors are not shown in the sketch. Regarding the smoke bypass I would not put it, it is another element that can add complexity to the design and durability, I really hope in a happy cold start without it. |
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Post by bulbius on Dec 27, 2017 14:14:10 GMT -8
Hello guys! I want to update you on the outcome of this project. I'm quite satisfied, the stove has been running for two months to date without problems. The space to be heated is large so when it's very cold outside we need to load the stove 3-4 times in a day. The white oven works nicely, after the embers phase it can even reach the full scale at 300° C. This is the final result: I made the painting with clay and glue flour. The top of the bench is made of concrete slabs but after some time they become too hot so I need to cover them with something. 
 This is the construction of the heat riser and firebox. The whole is insulated with aircrete blocks 
Octagonal riser made of 3 cm thick firebricks sealed together with refractory mortar. 
Here you can see the firebox with the port and the floor p-channel housing 
To support the bricks that form the top of the firebox (that is also the base of the oven) I used l-shaped iron rods. 
The door with a thermal glass stolen from an old electric oven.  The first layer of plaster made of cob. 
Insulation of the heat riser with 2.5 cm thick ceramic wool 
I wrapped the ceramic wool with a stainless steel sheet and I poured expanded clay between the two.  The 100 liters boiler made from an old tank with the two pipes connected to the hydronic system and the vertical pipe that handle the overflow sending it to the condensation discharge. The boiler rests on a kind of cup that collects its condensation.  The stainless steel flue that drain its condensation on the discharge located on the floor. You can see also the boiler overflow pipe. 
The copper serpentine that heats the sanitary water and the float valve that replenish the water of the boiler.  the top of the bell where the heat is maximum is made with stainless steel sheets surrounded with ceramic wool and aircrete blocks. The main goal of this stove was to heat the water inside the boiler so I insulated as much as I could the other areas.  
I didn't put a bypass so during a cold start it's necessary to light the fire slowly to heat the water contained in the boiler without producing too much condensation. Otherwise if you burn a full load during a cold start the smoke (mostly water vapour I guess) will escape everywhere. During the winter the stove never gets cold so there are no problems. I think this is due to the unconventional design (with boiler inside the bell) that make this stove different from what has been tested. Apart from that I'm satisfied with the build, the stove has a very good draw even when I totally open the door, the air intake is very comfortable and it can be adjusted easily in every burn phase. Soon I'll post some videos. |
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Post by matthewwalker on Dec 27, 2017 15:33:52 GMT -8
I love this heater! Nice work and thank you for sharing.
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. When the BBR reach the ember phase I could take some glowing charcoals and use it inside the fireplace. 
