Mini-Me heater

So I wanted to make a smaller version of the one I posted here: https://woodstoves.forumotion.co.uk/t165-let-me-introduce-myself

This is thrown together with scrap that's laying around and most of it is just tacked together for now. I added a secondary air intake to this one and I'm still playing with the draw and pellet feeder ramp. Seems to work pretty well and within about 25 minutes the top of the bell hits 550 and stays between 550 and 600 degrees. No smoke out the stack.

After it got up to temp I was messing around with draw and closed the secondary air intake. The temp shot up to 625-650.  

Suggestions are welcome and encouraged!

Of course, if I really wanted portable, I could have made one of these.  

Did I fart or something? Nobody seems to have any suggestions for me.

Enclosed all the insulation.....with welded steel.  Not a good idea, though it does work well.  The solid attachment of a weld means that it transfers heat to the outsides.  Still the firebox must be getting plenty hot.

Closed all the additional air intakes and the only air is through the ashbox and under the pellet tray.  Within 20 minutes the top of the bell reached 750 degrees and never left there.  That's hotter than I've ever gotten it with any combination of the additional intakes open/closed/partially open.  What does that mean?  Well, I guess that things like secondary air and the like aren't always needed.  

I guess it must be like an engine, you try something that shouldn't work and get an improvement!
It's a good looking stove :) whether it is a bit contrary or not ;)

Jack

I have been reading that less air is needed for these stoves. It seems that you have proven that theory.

Josjor wrote:

Of course, if I really wanted portable, I could have made one of these.  

 

:lol:    

Interesting the "negative" influence of the secondary air in the overall temperature output. Pekka Leskela in one of his videos proved exactly the opposite but he was burning wood. In your case, the secondary air seems just to mix with the combustion gases, does not react and reduces the overall temperature. Can you try and make the same experiment with plain wood and see what happens? What I noticed first is that the secondary air has a very short distance to warm up and second, secondary air openings may be too big, dragging too much cold air.

In reality I also use smaller openings for air supply in my stoves.

caotropheus wrote:

Interesting the "negative" influence of the secondary air in the overall temperature output. Pekka Leskela in one of his videos proved exactly the opposite but he was burning wood. In your case, the secondary air seems just to mix with the combustion gases, does not react and reduces the overall temperature. Can you try and make the same experiment with plain wood and see what happens? What I noticed first is that the secondary air has a very short distance to warm up and second, secondary air openings may be too big, dragging too much cold air.

In reality I also use smaller openings for air supply in my stoves.

I thought about both those things, the size of the secondary air and the temperature. Since it's all steel and is welded it's entire length, the temperature of the outside surface of that secondary air tube reaches almost 600 degrees so I'm not sure that temperature is the problem. When I messed with draw on previous burns, I closed it off so that it was down to about 20%. I still never reached the temperatures I did with it fully closed off.

The only thing I can think of is that maybe there just aren't any gasses left to be burned and when there's any secondary air added, all I'm doing is adding some 600-700 degree air to 1000+ degree exhaust. :?: 

I thought about trying it with regular wood, but with only a 3" tube it limits the amount of wood I can even get in there. One thing that is nice about pellets is that you get more material with more surface area in a smaller space. Anyway, with the feed the way it is, there's not really a good way to feed wood without changing out the feed pipe.

I never believe in results unless they're repeatable.   

This was the first time I had a chance to fire it up again. I ran it with the same plugs on all the additional air intakes. 16 degrees outside and about 20 degrees in the shop. Brrrrrr.

As I mention in the video, usually, while I get other things together, I'll shove a heat gun into the pellet feed and let it run for a minute or two in order to start some draft. This morning I decided to pretend I was living off the grid. I removed the exhaust stack and placed a lit cotton ball soaked in denatured alcohol there and replace the stack. Had a draft within seconds. Grid or no grid, I think this will be my new method.

700 degrees on top of the bell within 20 minutes. Pretty pleased and now I'll button up those secondary air intakes, weld the bell in place, and work on a pellet bin and stand.