An Accidental Discovery

[peterberg]

Matt,
Congrats, welcome to the select society of gas analyzer owners.
In order to interpret the results correctly, you need to know that the CO is diluted by the O². So, when the stove is running with a fair amount of excess air and a low carbon monoxide level this CO level isn't low at all, only heavily diluted.

The thing to accomplish is excess air and CO both at a low level. Moreover, it's possible to have fairly high end temps and high efficiency at the same time because of low excess air. This mutual cross-influence isn't easy to grasp, in my case it started to dawn on me after about a year of using this equipment.

In order to compare your future diagrams with mine, I'd like to suggest you start the Testo when lighting the stove. Wait until the O² level drops below 20%, stop the Testo and start again without saving the earlier measurements. The end of any run I would like to define at the point where the CO² is dropped below 4% for at least one minute. Some people, like the very knowledgeable guys from Lopez Labs let it run until 90% of oxygen level is returned. It's your choice which method to use and it's best to stick with it.

[matthewwalker]

Thank you for the welcome and the tips Peter, I need all the help I can get! You have made it clear over the last few years that excess air is a very, very important piece of the whole puzzle. I'm starting to grasp the concept, and I must admit that the first time I covered the feed and saw excess air shoot upwards really confused me. I get it now, or, I'm starting to. Here's a couple shots of the test data on my 8" J....

[peterberg]

OK Matt,
Your 8" system is running admirably clean, even the undiluted numbers CO AF are very low. To my surprise, the new T330-2 is measuring the excess air in percentages instead of Lambda. And you are right, excess air could be lower. The fuel you are using has a moist percentage of 20%. Maybe when this is lower, more volatiles at the same time would be produced and consequently more oxygen used to react with those volatiles. As far as I can see, gross efficiency could be more than 90%.

The low CO numbers, how many minutes are those at the same level?

[matthewwalker]

I need to do a proper run, but from the little I've tested, it's surprisingly stable at those levels. That was not a shot of the one good minute, it stayed that way as long as it was burning at full rate. It surprised me, how stable it was. You can see in this last picture from that run, it's been almost 10 minutes since the first picture above, and it's still improving regarding excess air.



It just didn't seem to change over the 30 minutes or so I played with it that night. I'll do a proper run in the next day or two and we'll see for sure. I picked up a small laptop that will work with the logging function, so I'll be able to post a full run. Did I read that you set sample rate at 10 seconds?

[akaleather]

Matt,

How did you build the broken riser to sustain the weight of itself and preventing it from becoming a "collapsed riser"?

[peterberg]

Dec 27, 2013 14:07:42 GMT -8 matthewwalker said:

Did I read that you set sample rate at 10 seconds?

Yes, that's what I am using. It's an acceptable rate to wait for. Is your 8" J-tube system built by-the-book or did you use a P-channel in that?

[matthewwalker]

Peter, the system is pretty much by the book, but the core is cast using my home brew mix and it has the window in front. Otherwise, stock ratios and proportions.

Akaleather, the riser in my broken riser build is 2" thick formed ceramic fiber, so it has enough strength to hold it's shape when laying over. It is carried on the lip of the barrel where it enters through a hole in the side.

[Donkey]

Congrats on the Testo, Matthew..
You got a picture of this stove?

[kpl]

Hi,

If this original finding could be transferred to a rocket-inside-a-bell masonry stove, like Peters' - what if the bend is located at the upper end of a riser, probably even bend it downwards - this should help avoid extreme overheating of the bell's ceiling, if the bell is not very high? Probably it's possible to create kind of a vortex inside the bell, to get more even heating.

This is my first post here, I just found this very interesting.
Basically I want to build as-simple-as-possible heater from the free bricks I have collected. I have also about 50 quite good fire bricks for a burn chamber and heat riser.
Heater will be located in my rented uninsulated woodworking workshop, It would be nice if heat mass could store enough heat to keep the room warm during paint or varnish drying, for 24 hours, if possible, as I can get there only after my day work. Last winter I heated with electric power, which was too expensive, when temperature outside got under -15 C.
Probably I should start my own topic, as I have several decisions to make before I start.

[matthewwalker]

Kpl, I don't know if your idea would work, but it's worth experimenting with.

Donkey, I apologize for jumping all over in this thread. The stove I was testing when I took those shots of the tester is my home heater. There are lots of videos and photos of that one. I will start a new thread with a test run of that one once I get around to doing a real test.

I don't have pictures of my broken riser test stove yet. I played with it for a week or so and have since disassembled it to switch gears on a different project in the same space. I will revisit it in a week or so and get some photos then.

[Cramer]

Well, I built the double barrel broken riser stove a week ago and put it in my bedroom for testing. I also have recently acquired a 330-2. I can verify this modification works just fine, I'm averaging around 82% efficiency even with fairly warm stack temps(350°F). CO is typically <50ppm during a burn, with O2 typically at 10.5% or so. I haven't had a computer that I could plug the 330 in to for the logging function, but that will change in the next day or two and I'll post some data. This opens up a lot of different format options, I'm still real excited about it.

Hi Matt!  You know what I am planning on doing.  What you built and put in your bedroom, is it broken (as we discussed earlier) or is it angled?

[morticcio]

Dec 28, 2013 12:30:30 GMT -8 kpl said:

Hi,

If this original finding could be transferred to a rocket-inside-a-bell masonry stove, like Peters' - what if the bend is located at the upper end of a riser, probably even bend it downwards - this should help avoid extreme overheating of the bell's ceiling, if the bell is not very high?

Take a look at the riser on Michel Wijnja's stove here. It has a right angle at the top which then directs the flue gasses down through a heat exchanger. This is all heavily insulated as it's primary purpose is heating water and not space heating. More photos on this stage of the build can be found on his blog

[kpl]

Thanks morticio, his other stoves are also extremely interesting. I have full head of ideas, but most probably the first thing is to start building something, just to get the feeling.

[Cramer]

Here is the rudimentary burner set up to test the idea of the "Slanted" riser instead of broken riser.  The wood used was not so dry deadfall and sticks from the woods.  Started with a hand full of pine needles and one blow on them immediately began a good draft.  Shown is the very beginning of the burn, the bit of smoke at about a minute forty in to the video cleared up completely when it began burning well.  In two hours it never smoked back even once.  Just thought you might like to see the test.

[matthewwalker]

Thanks Cramer, good stuff!