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Post by permaculturebob on Dec 14, 2018 9:00:30 GMT -8
Looking at some of the preliminaries of the DSR2 it almost looks like the batchbox and riser almost fit into the same footprint as the DSR. If that is the case I could modify my DSR without too much trouble, maybe get it back running the same day. My reason is mostly that a shorter batch box would be more to my taste, the original dsr design is a bit too long and narrow, also, it appears that when cooking, any pots seem to lower the temps above the port to the point where soot deposits on the spot where the pot is. Likely having that secondary burn start down level with the firebox would keep temps higher for a longer time giving a cleaner burn when cooking. The DSR is performing well (by my very loose standards), and i regularly shut down the primary air and run on secondary for most of the burn (although I have a square inch or two of leaks around the door supplying a little primary air). Temps above the port measured on the cook top are regularly between 800 and 1,000 F and I can see a very nice chaotic flame fountain for most of the burn. The only modest runaway I had was when I accidentally left the door open for over half the burn, that was when the temps topped 1000 (barely). Still, it was nothing out of control and closing the door and shutting down primary air quickly took the temps back down to the 800-900+ range. How expensive, and what is the learning curve on using a Testo?
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Post by peterberg on Dec 14, 2018 13:13:12 GMT -8
Looking at some of the preliminaries of the DSR2 it almost looks like the batchbox and riser almost fit into the same footprint as the DSR. Good thinking. Both have been tested in the same heat extraction setup, two barrels on top of each other. And the same system size also: 120 mm (4.72"). But, for the life of me, I can't find the @#$%%^&* drawings of the original DSR so I won't be able to check whether this true. How expensive, and what is the learning curve on using a Testo? Learning curve shouldn't be so steep since you are able to ask what to do here and Testo is able to offer documentation. But regarding price that's another matter, as far as I know there are two choices for wood combustion analyzing. The T 330-2, the one I am using is priced at € 1765 ($ 1994,56) these days and the T 330-i, a newer model controlled by a smart phone, priced at € 1512 ($ 1708), both prices excluding taxes. These prices are for the European market, I don't know whether or not it would be the same in the USA. Normally, the instrument need to be calibrated once a year which costs € 250 ($ 282.52) and a replacement cell when necessary € 500 ($ 565.03). As you can see, it's quite pricey for just testing your own heater. I use it more often of course, but it is still an expensive hobby.
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Post by permaculturebob on Dec 14, 2018 14:28:41 GMT -8
There were no actual dimensions given, other than in terms of fire bricks for the dsr, This has the sketchup file way down the page I found it here Testo does sound out of my range for asmuch as I might use it- like you said, an expensive hobby. I'll have to settle for my nose and watching the secondary burn characteristics
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Post by sksshel on Dec 15, 2018 7:06:10 GMT -8
I concur. However, even these 2 options have their challenges. I really don't want to climb up on my roof in the middle of the winter to smell the exhaust. Also, judging the secondary burn seems quite subjective. Add to that the fact that my viewing window into the upper shoebox is less than clear after only 1 month of usage. It feels like nothing more than a SWAG (silly wild a** guess) Some other observations: - when I use solely cord hardwood (oak and hedge), it's nearly impossible to get a good secondary burn. The bigger the pieces, the harder it becomes. - when I use small softwood (pine, 2x4s, red cedar) in small pieces, I get a very strong secondary burn. - when the softwood pieces are bigger than 3" diameter, it is harder to get a good burn. There seems to be a considerable amount of "art" to running one of these. I'm still learning every day. I'm a long way from any defined method of operation. I'd like to get to a point of more "Science" and less "Art" in this process. Perfection is unachievable. I'm looking for "good enough" at this point.
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Post by Vortex on Dec 15, 2018 10:11:39 GMT -8
Do either of you have a bypass damper for lighting? From my experience operating a similar setup I know mine doesn't work at all well without using one. It would just never seem to get going properly.
I run it from start with full primary air and bypass open until the chimney temp reaches 200*C/430*F, then I close the bypass and reduce the primary by about a third. I Think of it like lighting an old kerosene/paraffin pressure stove, you have to light the primer to heat the afterburner before it'll self sustain the burn properly.
I find the afterburner glass window perfect for controlling the burn efficiency - but I have a 1 CSA top box which forms a double vortex not a fire fountain - with the double vortex if the burning gasses stream out the top chamber then it needs more air, if they're just visible as a T shape then it needs less.
Would love to see some vids if you guys have some with views of both firebox and afterburner, but probably best posted in either the DSR or Vortex threads as it's off topic here.
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Post by permaculturebob on Dec 15, 2018 16:42:28 GMT -8
I use an old 12v fan mounted in the oversized flue pipe that runs about 8 feet up to ground level, then horizontal out away from the building, then turns and faces down. I have been leaving the fan on for the whole burn, and this is quite an effective substitute for a bypass damper control. Also serves as an aid just keeping air moving across the fuel like a bellows when it is getting started. My exhaust temps were way low measured on the outside pipe, around 100 or so(F) I don't have an observation window for the top box, so the secondary is only visible through the glass stove top . I'd love to be able to post videos, but so far I only have my website and have never explored posting vids, although sounds like a worthwhile learning process. For now I can only say temps on top regularly run mid 800s to mid 900 s(F) and the fire fountain keeps about a foot diameter circle cleaned of soot when it is running, but then leaves a fresh film of soot during the coaling at the end of the burn. After watching a circle of soot appear on the glass when boiling water in a pot, I started to think about the temperature loss of cooking, then the loss of heat to the air during normal operations, and have started to play with insulating the top with CF to see the effect. So far it does seem to enhance the burn temps in the secondary chamber, and I'm starting to think this may be the answer to getting a fully functional oven (over 400 F) while the burn is going on. It will also push more heat to the water tank in the farthest part of the bell. Since I'm pretty new at using this glass top, I'm a little concerned about creating temperature differentials and whether it might crack the glass due to uneven expansion. All the way at the bottom of this page I added recent pics of secondary flame through stove top and flame through the visions lid that is the firebox "door"
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Post by permaculturebob on Dec 15, 2018 19:21:54 GMT -8
I use an old 12v fan mounted in the oversized flue pipe that runs about 8 feet up to ground level, then horizontal out away from the building, then turns and faces down. I have been leaving the fan on for the whole burn, and this is quite an effective substitute for a bypass damper control. Also serves as an aid just keeping air moving across the fuel like a bellows when it is getting started. My exhaust temps were way low measured on the outside pipe, around 100 or so(F)
I don't have an observation window for the top box, so when it is clean the secondary is visible through the glass stove top .
I'd love to be able to post videos, but so far I only have my website and have never explored posting vids, although sounds like a worthwhile learning process. For now I can only say temps on top regularly run mid 800s to mid 900 s(F) and the fire fountain keeps about a foot diameter circle cleaned of soot when it is running, but then leaves a fresh film of soot during the coaling at the end of the burn.
After watching a circle of soot appear on the glass when boiling water in a pot, I started to think about the temperature loss of cooking, then the loss to the air during normal operations, and have started to play with insulating the top with CF to see the effect. So far it does seem to enhance the burn temps in the secondary chamber, and I'm starting to think this may be the answer to getting a fully functional oven (over 400 F) while the burn is going on. It will also push more heat to the water tank in the farthest part of the bell.
Since I'm pretty new at using this glass top, I'm a little concerned about creating temperature differentials and whether it might crack the glass due to uneven expansion.
All the way at the bottom of this page I added recent pics of secondary flame through stove top and flame through the visions lid that is the firebox "door"
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Post by Vortex on Dec 16, 2018 9:53:32 GMT -8
100F/37C is too low exhaust temp for a normally aspirated system, I have no idea what's OK with a fan driven setup. I would really recommend you get a proper insulated chimney.
An insulated afterburner will give better secondary combustion for sure. I wouldn't worry about cracking the ceramic cooktop, they designed to cope with cold pans being put on top when it's red hot. They have almost no thermal expansion.
videos can be uploaded to a free account and then linked to on the forum or on your blog etc.
800F/900F isn't too bad for the hotplate. I was regularly getting 1000F on the steel hotplate on my outside setup last summer. Something is wrong with the burn if you're getting that much soot though. I get a bit of a tint on the front glass a few minutes after lighting, still clear enough to see through though, and that's gone back to completely clear by 10 minutes, and I get none from the coaling phase.
If your wood is not properly seasoned and dry then that will do it, a lot of cold uninsulated mass in the firebox and afterburner will do it until it warms up, otherwise it's too much or too little air.
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Post by permaculturebob on Dec 16, 2018 10:16:11 GMT -8
100F/37C is too low exhaust temp for a normally aspirated system, I have no idea what's OK with a fan driven setup. I would really recommend you get a proper insulated chimney. An insulated afterburner will give better secondary combustion for sure. I wouldn't worry about cracking the ceramic cooktop, they designed to cope with cold pans being put on top when it's red hot. They have almost no thermal expansion. videos can be uploaded to a free youtube or vimeo account and then linked to on the forum or on your blog etc. Mine are here: vimeo.com/user44736525800F/900F isn't too bad for the hotplate. I was regularly getting 1000F on the steel hotplate on my outside setup last summer. Something is wrong with the burn if you're getting that much soot though. I get a bit of a tint on the front glass a few minutes after lighting, still clear enough to see through though, and that's gone back to completely clear by 10 minutes, and I get none from the coaling phase. If your wood is not properly seasoned and dry then that will do it, a lot of cold uninsulated mass in the firebox and afterburner will do it until it warms up, otherwise it's too much or too little air. I'll go ahead and move my reply to the DSR topic like you suggested, since it does have more to do with that type of system
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Post by permaculturebob on Dec 16, 2018 11:33:17 GMT -8
I have been struggling with the idea of a "normal" stack for some time. Permies has lots of that talk going on, and yet Ianto, whence most of this stuff started, had his exhaust a little above ground level through the wall and in the beginning That was a major talking point about how cool the exhaust was. some people ran their exhausts out through a standard dryer vent opening, and the clean cool exhaust was easy to disguise where wood burning was illegal. One of the fundamental differences in efficiency was how a cool exhaust meant more heat stayed in the building. I read one post about how his building site was special, dependable wind velocity and direction,and only a few people could get away with it, otherwise a "normal" draft had to be designed increasing exhaust temps and decreasing efficiency. My own experience tells me that one of the chief problems is simply the exhaust is down where you can smell it--and even if it has little odor, there's still lots of carbon dioxide. My fan is not very powerful, and since it operates at a cooler temp (all the way at the end of the exhaust) it and the pipe don't have to especially robust. In my original barrel bell rockets, just the push of the exhaust falling from the top of the riser was more than enough to create a good draft to push through 16 feet of horizontal bench, 6 -8 feet of vertical, and a few feet horizontal away from the building, although startup could be a little tricky, and when wind direction and velocity was erratic it could create some blow back occasionally. When I started playing with the batchbox design I found the fan was the only way to use my system with almost no smoke at start up. Playing with the dsr it was a godsend to start testing before everything was perfectly air tight. I'll save the rest of this rant possibly for a separate thread (is there an existing one on exhausts?)
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So if we both understand what I was saying, were you saying that your top glass does not soot up directly under a cool pot? I have noticed a lot of temperature increase when I lay a cf blanket on the stove top. I'm not sure if others have played with that idea, but it is a fairly easy way to control where the btus are used. It wouldn't surprise me if my main problem was the wood I'm burning. I'm also looking forward to some dimensions for the dsr2--I just noticed a new thread Peter put up, on converting DSR to DSR2. the sketches so far do not have the firebricks shown, so the cf board bb could be any size, and one post where he talked some about dimensions was incomplete and still in the testing phase, so I'll wait to start rebuilding what I have. It will be enough to install the plumbing for the water tank and get some hot water for right now.
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Post by Vortex on Dec 17, 2018 8:28:46 GMT -8
I think you'd have to be shedding heat from a barrel really fast for the ground level flue to work effectively, as that has to be your pump as you have no chimney effect to draw it through. A lot harder to get working on a batch stove without a barrel and a higher volume of gases moving through the system at times. Nothing works like a real insulated chimney, it forgives a multitude of sins elsewhere.
I don't have a ceramic cooktop, I have 15mm thick steel cooktop. I have a glass window in the front of the top chamber, that's what I was referring to.
Probably best if you let Peter guide you through converting it to a dsr2.
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Post by permaculturebob on Dec 17, 2018 10:30:10 GMT -8
I do plan to rely on Peter's results as far as clean burning and such, and it seems like all I'm really waiting for is the design parameters since the outer shell of my build can probably stay the same. I'd like to get as close as possible to whatever specs Peter comes up with
I would like a better definition of what the older j tube terms mean when looking at bb and DSR. People use them like everybody knows, but without a labeled diagram I'm just guessing.
What is the tunnel on the dsr for instance? where does the system csa come from? is it the cross section above the port, or just a ratio of the port size. Is the exhaust diameter critical relative to the "CSA", or can it be any size larger. In my system especially, it would seem air volume movement is a critical factor.
I agree with you about the bb design being less able to start the thermal siphon, which is really what this type of exhaust is. Starting it either with a fan or bypass is somewhat essential, although I do plan to start to experiment with turning it off sooner to give the system a slower movement allowing more time for complete combustion and possibly build up higher temps.
I haven't monitored the exhaust temps since the mass dried out, so that will be the next test, and maybe I'll end up with a remote thermometer on the exhaust outside and a rheostat on the fan.
For now the bell around the water tank is removed,( warmer weather), time to hook up the water tank. That will likely remove more heat for the final push up the chimney. Maybe the DSR2 will perform more like a j tube and I can get back to the good old days where I didn't need a fan
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Post by Vortex on Dec 18, 2018 7:14:31 GMT -8
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Post by permaculturebob on Dec 18, 2018 11:56:23 GMT -8
I used those dimensions to rebuild my RMH last year, what I have now is based on the sketchup drawing he did for the dsr.
I believe Peter said he would have dimensions for the dsr 2 sometime around the new year.
I'm not in a big hurry to rebuild, just trying to get everything back together; close tolerances, improvised materials and shaky connections make for a fun time
I'll check out the condensing flue, thanks
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Post by permaculturebob on Dec 20, 2018 16:04:48 GMT -8
The tank has plumbing connections, but I need a few 3/4 pex rings to make all the connections needed to hook into the main plumbing system. I've done a couple burns without water in the tank yet, but the new wet clay is still takingmost of the heat in drying out so temps are way low through the back half of the bell.
www.permaculturebob.org/2018/12/20/more-dsr-pics-double-shoe-box-rocket/This has some pics of my exhaust in case earlier words didn't describe it well, forgive the mess, it's what all us creative types need to thrive--would you believe lazy? For fun I got a temp reading during the first burn on the exhaust, and temps were around 50-60 degrees F while it was in the 40s outside I expect temps will stay in that range or below 100 most of the time.
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