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Post by peterberg on Sept 3, 2017 8:02:13 GMT -8
In my opinion, a fresh air intake isn't worth the trouble and inside a heater I would avoid it as the plague. Our house is built in 2014, an outside air intake was incorporated, the opening is beside the heater in the floor. Outside there's a simple stack of 1 m high, 3 m away from the wall. Sometimes it worked and most of the time it didn't. When the wind was at that side of the house the air supply was alternating between too much and too little, probably due to wind gusts. When the wind was on the other side of the house, sometimes the short stack outside worked as a chimney itself, competing with the proper chimney. In your case, the air intake in the heater should be heat resistant itself because there's always a chance the fire starts burning the opposite route. Here's a link to a comprehensive explanation of my point. woodheat.org/the-outdoor-air-myth-exposed.htmlActually, I spotted a defiancy in the chimney connection. It looks like it's too high from the floor, in such a system the exhaust opening should be as low as possible. Anything that's below and at the same height as the opening won't be heating up so your bench looks like it won't contribute to heat absorption. The door is a simple design indeed, it need to be a litlle bit smaller compared to its frame all around so there's room for a sealing rope in the very corner of the steel T-profile. A closing valve that exclude the bench from getting hot gases acts as a bypass indeed.
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grga
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Post by grga on Sept 3, 2017 9:59:18 GMT -8
Thanks for suggestions Peter and Jura. I do not like complications due to fresh air intake but my house is quite air tight and has active ventilation system with heat recovery. With no fresh intake I am afraid that I would probably need to slightly open one window while making fire which then need to be closed if not forgotten. Maybe other idea would be that fresh air would be supplied to the room from the heater through some valve and then it would naturally be sucked into the batchbox and nearly nothing to the room...
I do have another problem, the main bell must not be to wide due to available space I therefore planned to move the heater in the wall for 15 cm to have at least 10 cm space between the core and bell on both sides. Behind, up and below the core there is enough space. My supervisor (she) do not like the idea of digging the wall due to dust etc... would the performance of the heater be worse if I have only 5 cm space on both sides or even less (e.g. 7 on one and 3 on the other). I guessing the problematic would be overheating of the bell near the core (a bit higher cooling of the core) with similar performance?
I will indeed need to lower chimney especially (chimney inlet is at 45 deg) if I will move the heater into the wall.
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Post by peterberg on Sept 3, 2017 12:20:24 GMT -8
Thanks for suggestions Peter and Jura. I do not like complications due to fresh air intake but my house is quite air tight and has active ventilation system with heat recovery. With no fresh intake I am afraid that I would probably need to slightly open one window while making fire which then need to be closed if not forgotten. Maybe other idea would be that fresh air would be supplied to the room from the heater through some valve and then it would naturally be sucked into the batchbox and nearly nothing to the room... As I wrote, I did have the same problem, mine is a new passive house. One of the three preset values of the balanced ventilation unit, similar to yours, is altered to create a slight overpressure in the house. One of the fans inside the unit runs a bit faster than the other. This works everytime, the heater is operated this way once or twice a day last winter. And when the heater is closed and I would accidentally forget to switch to the normal preset value nothing is lost. I do have another problem, the main bell must not be to wide due to available space I therefore planned to move the heater in the wall for 15 cm to have at least 10 cm space between the core and bell on both sides. Behind, up and below the core there is enough space. My supervisor (she) do not like the idea of digging the wall due to dust etc... would the performance of the heater be worse if I have only 5 cm space on both sides or even less (e.g. 7 on one and 3 on the other). I guessing the problematic would be overheating of the bell near the core (a bit higher cooling of the core) with similar performance? If there's the right amount of ISA while one side of the core is very close to or even against one of the bell walls the bell would get a hotter spot, yes. Nothing wrong with it actually, the core will heat up the wall even at a distance of 20 cm. Performance-wise it wouldn't make any difference I'd say.
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grga
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Post by grga on Sept 4, 2017 9:32:56 GMT -8
As I wrote, I did have the same problem, mine is a new passive house. One of the three preset values of the balanced ventilation unit, similar to yours, is altered to create a slight overpressure in the house. One of the fans inside the unit runs a bit faster than the other. This works everytime, the heater is operated this way once or twice a day last winter. And when the heater is closed and I would accidentally forget to switch to the normal preset value nothing is lost. I also have 3 levels on my system (Paul). In winter I set on all of them a bit higher speed for output vent so just vice versa as yours (lower pressure in the house). This helps the unit not to freeze so fast in very cold days. I can take one of them and set it as you have to be used during heater burns... The 3-rd level can be triggered also by a switch and its duration can be set min 15 minutes and max maybe an hour - so I can use this preset for 1 hour and do not care about forgetting to change it back.... However the problem might be when outside is -10C or more then the unit can stop working even faster than in balanced mode - tis won't happen suddenly but after some time, maybe 1/2 an hour... Some units (my does not unfortunately) have dedicated button for the fireplace which does the same I guess. The reading from your link is fine and make sense and similarly does some other which you may found on the internet chimneysweeponline.com/hooa.htm. There is always some drawbacks. I think I will simplify and take room air.
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Post by peterberg on Sept 4, 2017 10:47:32 GMT -8
My system is one from Paul too, but I've a separate electric defroster installed.
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grga
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Post by grga on Sept 12, 2017 11:41:35 GMT -8
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grga
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Post by grga on Sept 20, 2017 10:12:41 GMT -8
Some slow progress made... Started to build. I used mix of 0-4mm quartz sand:lime:regular cement:clay (cca. 2:1:0.5:1). made the mould inside and pure ordinary concrete (sand:regular cement = 3:1) in it. To add some strength to it put thin mesh wire and add some glass fibers. In next steps I will need to decide what to do with bypass, fresh air intake, chimney closure. Between the layers of brick I have put a cardboard but probably it would be better to put some other thin material, maybe glass or stone wool (ceramic wool is hard to get and is expensive) which I will try to de-plaster it to be cca. 2mm thick only
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grga
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Post by grga on Sept 20, 2017 21:59:26 GMT -8
One side of batch box rests on the bell, what about the other end? 1) Usually some brick tower is made. Which is good solution, what I do not like so much about it: the floor is not empty-> some more problems at cleaning it takes more space in the bell 2) I could make concrete bridge from CAC. Is this ok regarding: -different expansions of materials and maybe damaging the bell? -at the bridge height the bell CSA would be smaller, would this influence the smoke flow
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grga
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Post by grga on Sept 20, 2017 22:41:27 GMT -8
I just realize that my chimney entry could be a bit too small. I have 18cm riser in diameter and 20cm chimney. In my calculation I take 1.5*CSA of riser, but I should have 1.5*CSA of the chimney?
my entry is 12cm high and 34 long so 12*34=408cm2 CSAchimney=314cm2 CSAriser=285cm2
Should I correct it - rebuild it now (I still can) or it is fine?
I should extend chimney entry to 12*39=470cm to be 1.5*CSAchimney
Or is good enough to have 1.5 CSAriser?
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Post by peterberg on Sept 21, 2017 0:25:45 GMT -8
1) Usually some brick tower is made. Which is good solution, what I do not like so much about it: the floor is not empty-> some more problems at cleaning it takes more space in the bell 2) I could make concrete bridge from CAC. Is this ok regarding: -different expansions of materials and maybe damaging the bell? -at the bridge height the bell CSA would be smaller, would this influence the smoke flow Both solutions are fine, I'd prefer the column as this is the least interfering with the bell construction.
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Post by peterberg on Sept 21, 2017 0:40:20 GMT -8
I just realize that my chimney entry could be a bit too small. I have 18cm riser in diameter and 20cm chimney. In my calculation I take 1.5*CSA of riser, but I should have 1.5*CSA of the chimney? my entry is 12cm high and 34 long so 12*34=408cm2 CSAchimney=314cm2 CSAriser=285cm2 Should I correct it - rebuild it now (I still can) or it is fine? I should extend chimney entry to 12*39=470cm to be 1.5*CSAchimney Or is good enough to have 1.5 CSAriser? What you have now probably would work. The csa of an 18 cm riser is 254 cm², multiplied by 1.5 is 382 cm². So this opening, being 408 cm² should be large enough. Remember though, that 1.5*riserCSA is a minimum value. Better to make it larger while you're at it. Have a close look at the space downstream of that opening, it shouldn't be any smaller than the exhaust opening itself. I am just signalling, it's easy to forget such a detail.
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grga
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Post by grga on Sept 21, 2017 10:30:12 GMT -8
Peter! thank you for that comment, I will enlarge it.
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grga
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Post by grga on Oct 9, 2017 1:14:06 GMT -8
I manage to insert firebox and put riser on top of it and isolate it with rock wool. Some images follow and two questions... to hold the batch-box I build a bridge from iron profile cca. 10x2cm with 2mm wall and put a 3 cm fire brick on top of it. QUESTION: I am guessing that this should be strong enough. Can it be problematic for metal profile to weaken at working temperatures? Should I put also brick tower to support the metal profile. If not needed I prefer to have empty space at the floor due to easier maintenance and inspection... For the riser I used Schiedel chimney pipes where I made longitudinal cut to allow expansions... Black parts are hi temperature silicone (1200 C). I isolated riser with 2 cm stone wool and put thin mesh around to support it, then I cover all with a layer of plaster (3 parts fine sand, 1 part CAC, 1.5 part cly). I use the same mix also for firebricks (inner walls of the bell). QUESTIONS: - I did not isolate lower part of the riser (batch box). I know this should probably be clever idea, but I do not see how to fix rock wool to the firebox - it seems complicated and could fall apart and block the bell if not done correctly... I see one solution using metal sheet put around riser and extending down to the bottom of the batch-box, but it sounds quite a complication. Is performance much worse without isolating lower part of the riser? - I plaster it. At first it seem to be a good idea but then after doing I got bit skeptic as the mesh would expand and caused plaster to crack probably it can also fall down. Any thought about that? If problematic I can put another mesh around it.
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Post by pinhead on Oct 9, 2017 4:23:18 GMT -8
You didn't need to cover the mineral wool with plaster; the mineral wool will easily survive in the post-riser environment. I'm slightly concerned about the longevity of the clay chimney pipes but with the longitudinal cut, maybe they'll last.
The lower part of the heat riser is where the majority of heat is concentrated for a large portion of the burn. As such, it should be insulated.
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grga
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Post by grga on Oct 9, 2017 22:21:22 GMT -8
Pinhead, thank you for suggestions. I will try to somehow isolate also lower part.
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