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Post by firerob on Oct 8, 2023 1:18:57 GMT -8
We flexed the p-channel open and welded it again. It's still not exactly 90°, but much better.
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Post by firerob on Oct 8, 2023 2:50:40 GMT -8
To fit the p-channel is a kinda tricky thing, but I think I got it now The vertical part of the channel is still too long. I will cut it when the firebox lid is fixed and insulated on top.
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Post by firerob on Oct 8, 2023 7:58:48 GMT -8
Except for vertical length and cut-out of p-channel the core is done!!   Peter, I need to ask again, would it not help against spalling if I would wrap the p-channel also in superwool? As double insulation from firebox and single insulation from bell. |
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Post by peterberg on Oct 8, 2023 12:52:13 GMT -8
As it is now, the horizontal duct won't spall, ever. The temperature in that spot won't get high enough, that's all. But.. if you wrap it in superwool, this could get wet from condensation and cause the duct to rust.
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Post by firerob on Oct 9, 2023 4:25:51 GMT -8
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Post by firerob on Oct 14, 2023 9:07:49 GMT -8
  New calculations showed that the ISA will get very close to the recommended maximum of 7.6m² (sidewalls, backwall, frontwall, ceiling). But then there's also some additional wall space in the small cubicle under the flue where the gases exit the bell. Don't know exactly how many m² that is but it could get me a little over 7.6m². How sensitive is this ISA of 7.6m² really? I could stay a little more under this value, but that would mean to cut the top layer of the double skin (on which the L-profiles for the ceiling will rest) in half (to lower the height of the bell). Is this worth it? What is the recommendation here? (We are talking about plus/minus 0.2m², I think) Also, the inner wall of the double skin will be split firebricks (mortared, like firebox + riser), but I'm planning to NOT mortar the split firebricks for the ceiling (they will just lay on the inner wall of the double skin and on the L-profiles (with superwool under). Like in the Mallorca build. Did I see this right in the video?
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Post by peterberg on Oct 14, 2023 12:28:59 GMT -8
New calculations showed that the ISA will get very close to the recommended maximum of 7.6m² (sidewalls, backwall, frontwall, ceiling). But then there's also some additional wall space in the small cubicle under the flue where the gases exit the bell. Don't know exactly how many m² that is but it could get me a little over 7.6m². Normally, I calculate the bell as if there wasn't a core in it at all. So as if all 4 sides were closed. The core will extract very little heat at first and at the time it extract more the temperature is already higher inside the bell. The bell Internal Surface Area maximum is there to ensure the thing will start always. So please, apply my method and when it's equal or less to the recommended value you should be fine. How sensitive is this ISA of 7.6m² really? I could stay a little more under this value, but that would mean to cut the top layer of the double skin (on which the L-profiles for the ceiling will rest) in half (to lower the height of the bell). Is this worth it? What is the recommendation here? (We are talking about plus/minus 0.2m², I think) The ISA is quite sensitive, but would be mute with a bypass. In your case, there isn't such a thing so now it comes down to the quality of the chimney. Is it high enough, like 5 meters? Straight up, isulated outside the dwelling, no higher buildings or trees in the near vicinity? In that case, you will almost certainly be fine. But be very careful while it isn't completely dry yet, which will take several weeks of running it every day. Also, the inner wall of the double skin will be split firebricks (mortared, like firebox + riser), but I'm planning to NOT mortar the split firebricks for the ceiling (they will just lay on the inner wall of the double skin and on the L-profiles (with superwool under). Like in the Mallorca build. Did I see this right in the video? Sorry, not correct. The bricks of the Mallorca build are mortared together. You could get away with it when just layed dry if it's properly sealed with superwool on top and at least one layer of ordinary bricks on top of that which are mortared together. Are you sure you want split bricks as bell ceiling? |
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Post by firerob on Oct 15, 2023 1:38:54 GMT -8
Normally, I calculate the bell as if there wasn't a core in it at all. So as if all 4 sides were closed. The core will extract very little heat at first and at the time it extract more the temperature is already higher inside the bell. The bell Internal Surface Area maximum is there to ensure the thing will start always. So please, apply my method and when it's equal or less to the recommended value you should be fine. With your method I calculate 7,755m² (2 sides + front + back + ceiling). If I substract the missing part of the front wall (where firebox meets bell) then it gets down to 7,56m². We have only 4m of flue (aluminium) straight up. Not insulated outside of the house (but could be done somehow, I guess). I'm still not sure if I should lower the height of the bell by 5cm, which - with your method - would result in an ISA of 7,59m². (Not taking into account the cubicle under the flue) Sorry, not correct. The bricks of the Mallorca build are mortared together. You could get away with it when just layed dry if it's properly sealed with superwool on top and at least one layer of ordinary bricks on top of that which are mortared together. Yes, that is the plan; firebricks layed dry with the bigger gaps stuffed with superwool, then superwool on top of the firebricks and then a mortared layer of normal bricks. And maybe even a layer of earth plaster on top of that. Are you sure you want split bricks as bell ceiling? No, I'm not sure, now that you are asking. We have the split firebricks here already, but I'm positive, we could exchange them to the 6,5cm ones. What do you think?
By the way, the distance between top of riser to bell ceiling is 49cm (respectively 44cm, if I lower by 5cm)
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Post by peterberg on Oct 15, 2023 3:58:22 GMT -8
I'd think your bell is somewhat at the large side of things. Minimum space above the riser, commonly called top gap, is the same as the system size (yours is 18 cm, yes?). Twice the system size is plenty, so you have some space. Lower the bell with one brick and you are there. Your chimney is just so-so, see further down this post.
Best to exchange the ceiling bricks for 6.5 cm thickness, much more sturdy than splits. Some extra mass is good.
Your alu chimney pipe may be a liability, better to exchange that to ordinairy steel stove pipe. The part outside the dwelling insulated if you can do that. Initially, the temperature of the gases won't be high so you tend to think the alu pipe is alright. In the depth of winter you might run the heater three times a day, heat in the pipe goes up and at some point it will fail. Not a good prospect, I'd think.
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Post by firerob on Oct 17, 2023 8:49:03 GMT -8
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Post by peterberg on Oct 17, 2023 10:11:36 GMT -8
After finishing, the heater contains lots of water. Better start with a small fire in front of the port (not in the port) and add some when this is going well.
Before you do that, see what amount a full load would be, load it all lengthwise, from front to back. Keep at least 5 cm space above the fuel and behind it.
Then, take the amount of half a load and burn that. Every day at the same time for about one week. Then increase the amount to 3/4 load and burn that daily for another week. Once that's done, increase again to a full load, daily for a third week. When this is all done, the heater could be declared reasonably dry. Please don't overfeed it, running it for hours at a time is definitely not good. Run it just more often, morning and evening for example.
There are two ways to load a batchrocket: the 'normal' way, small fire in front of port and build on that. The second method (my preferred one) is the upside down method. Biggest logs first, and higher up the thinner pieces. On top a handful of tinder and a barbecue lighter. No newspapers, this will get very messy.
All fuel front to back as mentioned before, no criss-crossing, campfire or log cabin style. The gaps between the pieces are adequate for burning. Don't throw logs in, you'll run the risk of damaging the rear wall. Leave some glowing charcoal and close the air inlets, the fire will go out. Start the next fire on top of the charcoal, it'll burn easier through. Self-ignition temperature of charcoal is about half compared to wood itself. The fire will creep very easily under the bigger logs to the air inlet just because of that.
Ehrmmm... that's about it. Succes!
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Post by firerob on Oct 19, 2023 8:25:02 GMT -8
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Post by firerob on Oct 19, 2023 8:48:14 GMT -8
Leave some glowing charcoal and close the air inlets, the fire will go out. You said b4, never to close the secondary air inlet (because of the cooling effect against spalling). With the above comment, did you mean close first AND second air inlet during coal stage?
Ehrmmm... that's about it. Succes! Thanks a lot! For all of your advice! I can't really tell you how much you helped! Without you, this heater would not be what it is now! It'll perform awesome, I know it! Thank you very much! Bedankt, from Zsofi and me -Rob |
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Post by peterberg on Oct 19, 2023 12:06:59 GMT -8
You said b4, never to close the secondary air inlet (because of the cooling effect against spalling). With the above comment, did you mean close first AND second air inlet during coal stage? Yes, that's correct. |
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Post by firerob on Oct 21, 2023 8:20:21 GMT -8
Finishing touches and first small test fire, which started surprisingly nice after pre-heating the flue with a gas torch for a short bit. After about 1/2 hour it was going fairly strong with slight rocket sound. This video is from the first of seven 1/2 load fires. It still needed some help with flue pre-heating, but once started it's going well. Once it reaches ~45°C on the lower thermometer the rocket starts and the draft pulls the flames into the riser (again, with a pre-heated flue!). The max temps on the thermometers were 120°C / 50°C (upper thermometer about 65cm / lower thermometer about 125cm from ceiling; ceiling to floor 204cm). The outside of the bell started to feel warm after a while. There's a lot of condensation at the doors and on the bottom under the flue. So far, I'm very very happy about the performance!! Once this baby is dry, it's gonna be friggin' awesome!!
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