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Post by masonryrocketstove on Jan 6, 2024 9:07:32 GMT -8
the chimney is as followes. 1meter in the bell (insulated with ceramic wool) 1 meter insulated chimney to the ceiling of the room I have a clay rectangle old chimney 200mm running 4-5meters and I've put a 180mm uninsulated chimney pipe inside the clay chimney. In the empty space between clay chimney and new chimney I filled it up with vermiculite for insulation. The cowl is just a beefy slab of concrete to prevent rain from going in. This thought just now dawned on me as I was playing around with some vermiculite-clay mixes I tried to make insulated castable out of.. and the vermiculite still hasn’t fully dried out several months later.. What are the chances that some dew, rain seepage, or even moisture from a hot water / steam source in the house (like a nearby washing machine, dryer vent, bath/shower or kitchen) has gotten underneath that concrete slab cowl, into your 4-5 meter run of clay chimney ..and has soaked into the vermiculite fill around the pipe? Reason I ask is that once vermiculite insulation gets wet, it holds that water so aggressively that it sometimes never fully dries out until you heat it in dry air to over 210°C / past boiling point for a couple hours. (Martyn warned me last summer how hydrophilic vermiculite is and I should have taken his word for it lol. Makes total sense.. vermiculite is used a lot in gardening soil to soak up huge amounts of excess water and then very slowly release some moisture back to the plant roots over time.) While poking at my still-damp failed castable experiment, it occurred to me that if any water got into your vermiculite chimney fill, it could be staying wet and cooling that pipe super quickly.. almost like an evaporative cooling tower. Might explain why the inside of the chimney pipe is condensing flue gas, ..and it might be why draft has been more sluggish than expected with your stove configuration. Just a thought.
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jonasp
Junior Member
Posts: 102
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Post by jonasp on Jan 9, 2024 0:33:15 GMT -8
martyn Vortex thanks for replying it gives me a peace of mind that it is vapor. Today with a blue sky i can clearly see it is vapor. masonryrocketstove wow thank you for the extensive explanation! outside humidity is around 90 past couple of days so the air is pretty much saturated. I actually was thinking that wet vermiculite could be the problem although the steam is clearly coming from inside the pipe.. I changed something which should prevent any moisture getting into the vermiculite. I still have an opening in the space where the vermiculite is not completely sealed off and any moisture should get away. I do plan to make changes after winter and might remove the vermiculite and fill it back up with completely dry one, just to be sure. (kinda annoying since i actually ordered perlite instead of vermiculite, didn't think much about it back then..) I can't run the system with full bypass open it'll overfuel. I'm not sure how much condensation happens inside my chimney, it for sure does on the brick chimney cowl. So the problem you see if too much condense happens in the chimney pipe it'll corrode the aluminum pipe faster? I'll need to read your comment again more carefully to exactly understand everything in there.. Before reading your comment I did 2 burns with a longer bypass open to heat the chimney faster, it actually improves my complete burns, no overfueling at any point, nice fast spinning vortex. I get a faster draft in the system from the start so the vortex spins faster from the get go which prevents overfuel for me. (it's very cold past days so need to check if it'll have the same effect on milder days) I've always gotten overfuel when the draft was a bit lacking and the vortex was spinning a bit too slow which causes too much heat buildup in the afterburner i think. Very interesting learning so much on this forum.
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Post by masonryrocketstove on Jan 9, 2024 14:53:29 GMT -8
So the problem you see if too much condense happens in the chimney pipe it'll corrode the aluminum pipe faster? I’m sorry, I was thinking your chimney pipe was steel. I must have missed that in your earlier post. Yes, flue gas condensate is corrosive to aluminum pipe, too. Corrosion won’t happen quickly, but frequent condensation will speed up the corrosion rate a little bit. Best to keep the chimney dry if you can. Sounds like leaving the bypass open a little longer may work well for this heating season until you can open up the chimney next summer and inspect it. If the insulation has gotten wet on the outside of the pipe, you’ll want to remove all the wet vermiculite and replace it with dry insulation. Then find a way to keep that insulated area well sealed from moisture getting in there again in the future.
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Post by Vortex on Jan 10, 2024 5:31:27 GMT -8
Is the chimney pipe really Aluminum or is it stainless steel?
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jonasp
Junior Member
Posts: 102
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Post by jonasp on Jan 11, 2024 1:19:28 GMT -8
Is the chimney pipe really Aluminum or is it stainless steel? Oh I'm wrong it's made of RVS 316L I have the feeling my system is very sensitive to draft, too little draft and heat buildup in the afterburner is most likely to cause small overfuel (flares of smoke going over the shelf). I also have the feeling if the draft is too slow at the start until peak the fire spreads faster to the bottom of the woodstack since less of the flames gets drawn to the firebox exitport. (which Vortex has mentioned a couple of times that my burns look like they burn from the bottom to the top) Not quite sure this is really the case but today I changed some small things to the top shelf which gave a slower spinning vortex and I had the feeling the fire spread faster to the bottom. (caused a small overfuel situation) I try to stack the wood from thick to thin leaving as little gaps as possible and light it with some kindling under the port. Vortex do you stack wood completely to the top including the sides so you have a flat top and light it in the middle under the port or do you leave some space on the top sides? (My burns spread down and sideways but mostly the sides are slower to burn than the middle) Hope i make any sense with this explanation
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Post by Vortex on Jan 11, 2024 3:06:35 GMT -8
Thought that was probably the case - is the stainless chimney pipe straight, rigid and smooth or flexible and wrinkly? A buildup of heat in the afterburner is not the problem, I've had mine up over 1000*C without it overfueling. The issue is that when the draft is too low not enough O2 gets drawn into the firebox and so there's not enough for the combustion in the afterburner, and so unburned gasses then flow out up into the top chamber - which is what you see as overfueling. If your chimney insulation is wet or damp then that has a huge effect on draw. I know someone who was given a stainless insulated chimney that had been left outside lying in long wet grass over winter. When he installed it the fire was very difficult to light, filling the room full of smoke until the fire was going strong, then it would work OK until it got to the coaling phase when it would gradually go into reverse and fill the house with CO. All because the rockwool insulation in it was wet. Vortex do you stack wood completely to the top including the sides so you have a flat top and light it in the middle under the port or do you leave some space on the top sides? (My burns spread down and sideways but mostly the sides are slower to burn than the middle) Hope i make any sense with this explanation Here's a couple of old pics. I now have a steeper V floor and slightly narrower firebox, and my wood these days is mostly small rounds upto 4" but otherwise the same:
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jonasp
Junior Member
Posts: 102
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Post by jonasp on Jan 12, 2024 0:05:34 GMT -8
Thought that was probably the case - is the stainless chimney pipe straight, rigid and smooth or flexible and wrinkly? A buildup of heat in the afterburner is not the problem, I've had mine up over 1000*C without it overfueling. The issue is that when the draft is too low not enough O2 gets drawn into the firebox and so there's not enough for the combustion in the afterburner, and so unburned gasses then flow out up into the top chamber - which is what you see as overfueling. If your chimney insulation is wet or damp then that has a huge effect on draw. I know someone who was given a stainless insulated chimney that had been left outside lying in long wet grass over winter. When he installed it the fire was very difficult to light, filling the room full of smoke until the fire was going strong, then it would work OK until it got to the coaling phase when it would gradually go into reverse and fill the house with CO. All because the rockwool insulation in it was wet. Vortex do you stack wood completely to the top including the sides so you have a flat top and light it in the middle under the port or do you leave some space on the top sides? (My burns spread down and sideways but mostly the sides are slower to burn than the middle) Hope i make any sense with this explanation Here's a couple of old pics. I now have a steeper V floor and slightly narrower firebox, and my wood these days is mostly small rounds upto 4" but otherwise the same: It's a smooth pipe and there're only 2 30 degrees at the start (you can see that in picture). That's a much better explanation of my sometimes occurring overfueling situation. I never had a problem with reverse draft but it might have influence for sure. Only thing is I would think the moist that could've gotten in, shouldn't be a lot and might be dry by now but i can only be sure when i double check.. That's pretty much a perfect stack. Sometimes it's hard to make it as pretty with little gaps but I do see when a larger gap exists fire will spread fast to that gap. Have you ever experimented with lighting a bit left and bit right of the exit port so the fire spreads more equally from top to bottom? Now it always spreads in a V shape, you can see it nicely in your second picture. (maybe could have effect of faster build up but slower peak, not sure though it might just be even faster since you have 2 points where the fire spreads)
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Post by Vortex on Jan 12, 2024 6:03:46 GMT -8
It might be an idea for you to get one of those cheap plant moisture meters and insert the probe into the vermiculite, if there's damp getting in it will equal out thorough the vermiculite quite quickly, and so that way you could keep an eye on it remotely.
I don't have any issues with the stack burning down too fast. It will always burn down the center a bit faster than the sides, but I put a large piece in the bottom of the V grate and that slows it's progress in the middle and evens the burn out quite well. I stack the wood tighter in windy weather and looser in still weather. If there is any air leaking up through the ash-trap then that will make it burn down the center quicker.
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Post by masonryrocketstove on Jan 12, 2024 7:04:50 GMT -8
Oh I'm wrong it's made of RVS 316L That’s great to hear. 316L is the most corrosion-resistant alloy used for all-fuel chimney pipe. It’s also a lot more heat tolerant than aluminum. After telling you to leave the bypass open to get the chimney pipe hotter, I was a little concerned when you then mentioned it was aluminum. ( Aluminum pipe isn’t allowed in most places by International Building Code for use in solid woodfuel burning chimneys because it can’t withstand high heat or creosote chimney fires.. but a thermal mass / storage stove usually has lower flue temperatures and cleaner exhaust without creosote, so sometimes mass heaters can quietly get by using aluminum.) Very glad to hear you actually have the best quality pipe there is. At the time when you posted this, I thought the problem was solved (for this heating season at least, until you can inspect it this summer) but the more recent posts sound like you’re still having sluggish draft? If your chimney insulation is wet or damp then that has a huge effect on draw. I know someone who was given a stainless insulated chimney that had been left outside lying in long wet grass over winter. When he installed it the fire was very difficult to light, filling the room full of smoke until the fire was going strong, then it would work OK until it got to the coaling phase when it would gradually go into reverse and fill the house with CO. All because the rockwool insulation in it was wet. I’m with Trev on this. 100%. Even a tiny amount of moisture in the chimney insulation can have a huge cooling effect on the flue gasses, and that will really, really slow chimney draft, making for much poorer combustion cycles than you would see under normal chimney conditions. Only thing is I would think the moist that could've gotten in, shouldn't be a lot and might be dry by now but i can only be sure when i double check.. Because the insulation is vermiculite fill, and because the gap between the 180mm chimney pipe and the 200mm clay flue is only 10mm.. and because that very narrow gap is 4-5 meters tall.. I can virtually guarantee that you wouldn’t have been able to dry it out completely yet. ..I honestly don’t think you’d ever get wet vermiculite completely dry while it’s in that 10mm gap, for that 4-5 meter height of chimney run. Assuming moisture is the problem (assuming the vermiculite *did* get wet,) and you’re still having these draft issues, I don’t think you’ll be able to see an optimally good burn cycle with the stove functioning as it should until the damp chimney insulation is replaced, (making sure that gap is sealed against moisture to prevent it getting wet again.) Edit: looks like Trev responded while I was writing this. His moisture meter suggestion may be a really good idea, even if just for monitoring in the future after replacing the damp insulation, and to know whether that gap has stayed dry once you find a fix for moisture-sealing it.
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jonasp
Junior Member
Posts: 102
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Post by jonasp on Jan 17, 2024 23:56:45 GMT -8
As long as i play a good game of tetris with the wood logs and put 2-3 bigger pieces at the bottom the burns are going pretty well. I think i didn't stack good enough having too many air pockets between wood. Now when i have an overfuel (which happens not that often anymore) i can most of the time fix it by opening the primary air a tiny bit. When the temperature outside is around 0 degrees the draft is perfect it does take a bit longer to get going when It's warmer. I'm thinking about drilling a hole from the bottom to check the vermiculite. It shouldn't be possible to get even more wet so the probe would be good to know if it's wet or not though.
Great to hear i have a good quality chimney pipe! The vermiculite gap is bigger since the clay chimney is rectangle (width is 200mm) and the stainless steel pipe circle the smallest is 10mm.
(next week warmer temps so let's see how it reacts)
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jonasp
Junior Member
Posts: 102
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Post by jonasp on Jan 27, 2024 2:08:47 GMT -8
So I've drilled a small hole and got some vermiculite from the bottom. It feels dry so I assume that's not an issue. The stove works perfect when it's cold but as soon as the outside temperatures are higher the draft seems to be a little bit lacking. It's not a big difference but seems to matter in my configuration.
When there's strong winds with strong wind gusts you can see it struggling since the O2 is changing a lot all the time. A little bit of wind and it works pretty good. I hope a good chimney cowl will improve the draft a little bit (some cowls claim they improve draft like the windkat and the rotating one, still in doubt between these 2) and temper the strong winds a bit.
At the moment I'm not using the bypass anymore at the start but just leave the door open a crack bit untill it gets going (roughly 15min)
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Post by Vortex on Jan 28, 2024 6:03:19 GMT -8
I was amazed how much a poorly designed cowl can restrict the draw. Opening and closing the door and bypass at the same time works best on mine.
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Post by willemdefilm on Feb 4, 2024 3:55:29 GMT -8
I there, I'm New to the forum but have been running a 130mm vortex stove for about 2 months now. I build it exactly to the dimensions as published by 'vortex' on the permies forum. I've read probably every post of vortex and fox and would like tot thank the a lot foe the effort they've made over the jears!! Very happy with our stove now, its hooked upto a water heating coil wit buffer tank feeding the underfloor heating, works the charm in our strawbale house. ( and yes I am fully 100% aware of the issues that come with heating water, expansion, steam explosions etc etc. Please don't worry) Anyway I ran in to the same overfueling issues as jonasp explains in thjs thread. I tried different batches of wood (hardwood vs soft wood), different amounts of kindling and different sizes of wood, but kept having the same overfueling issues. The entire batch of wood be alight after 20 minutes and the afterburner just couldn't cope. At least that was my conclusion.... Then I took out the viewing window of the fire chamber and put a temporarily steel plate in with an adjustable air hole located completely at the top of the fire chamber. The idea was to be able to supply more/enough air to the vortex as this air runs along the ceiling of the firebox. Also this air would be directed more on top of the wood in the firebox, so the batch burns down top to bottom nicely, and prevent the wood to catch fire all in once. This has made a HUGE difference in my stove, I can now even reload the stove while running whithout overfueling. I believe the stove automatically draws less air in at the bottom now since part of the draft is 'taken away ' by the new higher placed air inlet. Here a movie running on pine, hence the crackling and the sparks drive.google.com/file/d/1woF2sKNAozAcNqQ5oy9HMB-rPuq_4-Vw/view?usp=drivesdkAlso a picture where you cansee the air hole at the top in the door, in the movie I already had a cover over the air hole to prevent any sparks from flying out. drive.google.com/file/d/1wuAkFR35hs1P_Ak93XIVTkj9lburwiLM/view?usp=drivesdkPerhaps sharing this can help others.
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Post by Vortex on Feb 4, 2024 5:34:48 GMT -8
Hi willemdefilm, I'm interested to see your movie, but the link requires a google account to view, can you please make it public? Thanks.
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Post by willemdefilm on Feb 4, 2024 7:26:01 GMT -8
Fixed the movie issue, I hope....
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