oxygen control for garn

[heaterman]

I'd love to monitor a full burn with my combustion analyzer both with and without the O2 sensor engaged and observe what CO and efficiency are doing over the course of a load. That would really tell the story. I'm betting that the O2 sensor controlled burn would show really low CO levels.

Steve - This would be an interesting exercise. I just wonder how accurately you could duplicate a burn cycle. Even splits from the same tree aged in the same manner for the same amount of time are going to burn differently. I think you would need to do a longer study of multiple burns over the course of a season to get averaged results for both combustion efficiency, Delta T comparisons (thermal yield), and solid fuel consumption.

Tom - do you have any chrono data for the phases of a non-modified GARN burn? Let's say for a 2 hour burn, how much of the burn is occuring during rich, stoich, and lean phases? I'm a believer in the 80/20 rule for many things. I would offer a hypothesis that 80% of the burn is occurring within stoich, or within 20% of stoich on either side. If that assumption is correct, you are optimizing the burn phase during less than 20% of the burn. I am sure your system is modulating the input air continuously, as you say, but I just wonder how much "return" their may be on this type of investment. Can you pull data from the controller and plot the flow curves for P&S air flow over the course of a full burn?

I am not at all criticizing your effort. I commend it. I am just curious as to how much more thermal yield you are getting from optimizing the burn in this manner. If you can get more close to a 20% increase in Btu yield from the fuel using this method, I think it is well worth the effort. If it is less than 5-10% increase in thermal yield, it is more of a fun exercise (and maybe a cleaner flue). You sure have us thinking though! :coolsmile:

I think about the best one could do and still have the test resemble field conditions would be to check both loads for moisture content, use the same number of pieces so as to approximate the size of the wood and weigh each load. Considering those things, one can understand why the EPA test is done with kiln dried wood cut into 4"x4" square pieces. The old common denominator thing..........

 

[Jim K in PA]

I think about the best one could do and still have the test resemble field conditions would be to check both loads for moisture content, use the same number of pieces so as to approximate the size of the wood and weigh each load. Considering those things, one can understand why the RPA test is done with kiln dried wood cut into 4"x4" square pieces. The old common denominator thing..........

Bingo! That is exactly why I like averaged data from real world operating conditions rather than a single "standardized" test using parameters that have no appreciable correlation to those real world conditions.

Engineers are weird (I know, I are one ), but scientists are weirder . . . :lol:

 

[Nofossil]

What I'm hoping for is that data obtained from the lambda sensor can be used to create a nominal burn profile that's closer to optimal than the fixed ratio that we're stuck with from the factory.

Even if there aren't any other clues that we could get from simple & cheap sensors, a simple time based primary / secondary ratio curve seems like it would be better. In my own system, I divide the fire into phases:

1) Startup - temperatures are rising quickly, equilibrium not yet established.
2) Main burn sequence - output at 75% of rated value or higher, boiler at operating temp.
3) Burnout - just coals. Output is tailing off.

These phases are inferred by time and temperatures. I use these phases to manage loads and flow rates, but I don't do anything with the primary and secondary air. I'd love to be able to make good guesses about combustion air from some variant of this phase logic.

The EKO controller has one major flaw - it runs the blower at full speed any time that the outlet temp is significantly below setpoint. This means that it runs the blower full tilt at startup (not good) and during burnout (a complete waste).

One Froling feature that I'd kill for is the fire start logic. It manages blower speed and dampers to automatically nurse a fire through startup. I doubt that lambda sensors play much of a role in that, but I don't know.

 

[TCaldwell]

I guess simple minds think alike! Anyway, with the rain and snow last night,i had the day off, i monitored about 1.5 hrs of burn at .5 hr intervals with the testo 327 combustion analyser, i did load between the first two readings, test 1 flue temp 268--- co2 13.32%----effiency 85%---- excess air 49.3%---- ppm co 97----- o2 7% test2 flue temp 237---- co2 13.13%---- effiency 85.9%---- excess air 51.4%--- ppm co 115----- o2 7.2% test3 flue temp 225 ---- co2 13.13%----effiency 86.3%---- excess air 51.5%---- ppm co 85---- 02 7.2%---
pretty consistent results. Tomorrow i will start monitoring from beginning to end, the wood burnt today was a very dry mix of split cedar and oak. Maybe heaterman would be able to test a stock garn from beginning to end at preset intervals, and we could compare notes? Jim , no offense taken, my wager is that i can control 80% of the burn cycle within 2%, and that 40% of the stock garns burn will either be under or over aired.

 

[heaterman]

TC What was your water temp during those tests? That can make a big difference in the efficiency numbers as well as flue temp. Those are pretty impressive numbers. I just walked in the office from a job with a new 1500V Garn installed and piped up. It's burning it's first load as we speak. I'll be back there tomorrow and bring the Testo along with to do some sampling. I'm really curious about this one because the guys wood leaves a lot to be desired. Also anxious to see what the water temp is in the AM as it will be sitting there not circulating with the prototype of our insulation jacket on it. The owner is going to check the water temp before he goes to bed and we'll see how much standby loss we have in the morning.

 

[TCaldwell]

Heaterman,water temps were between 150 and 170 when i took readings, i will note when i monitor tomorrow, tell me about your garn jacket, my house is on the market, might have to take garn with me.

 

[heaterman]

might have to take garn with me

Now that is the sign of a true believer.

I'll see if I can take some pics tomorrow of the prototype wrap. The production version will have an aluminum pebble facing on the front not the polypropylene.

 

[Como]

What is a 1500V, is this different to a 1500?

I am looking at getting one this winter, in the process of designing the building, it will be capable of housing 2, we have a big heat demand but small pockets.

 

[heaterman]

What is a 1500V, is this different to a 1500?

I am looking at getting one this winter, in the process of designing the building, it will be capable of housing 2, we have a big heat demand but small pockets.

It's a 1500 with a vertical flue vs the original (H) model which has the flue discharging out the back horizontally.