PDA

View Full Version : Rocket stove fail



Tylerdurden
11-23-2011, 07:37 AM
Fired the stove for the first time. Clay is still very damp so a slow cure start was in order and I was warned that is will suck so much heat the draft will be hard to keep going. Started off slowly with newspaper an kindling and soon she was making the sounds rocket stoves get their name from. Ran fine for about 15 minutes till the flames slowed then woosh she backed right up into the house. I was ready with a very large furnace fan and started pulling smoke out but it got pretty dense for a while. Come to find out that the ash door to the chimney was leaking like a sieve and my boy was watching it from the top of the chimney. Said he watched the smoke rising then it just collapsed right down. That is the issue with sucking every last BTU out of the exhaust. New door being picked up today and will try again after installed.

Picture is not mine but very similar. (don't do photos)

http://lh6.ggpht.com/_3ReOSq1TitE/Sf-KuF_SdkI/AAAAAAAACkI/fi-k2PPZNXw/4e-fox_circle_stove.JPG

Andrew Craig-Bennett
11-23-2011, 07:42 AM
Umm. thoughts...

Try a shielded (double wall) flue?

Try another shape of flue cap?

Try a longer flue (above roof pitch)

Tylerdurden
11-23-2011, 07:49 AM
Nope. Just air leaks. Once the door is replaced I should be fine. Rocket stoves are hard starting when cold. Once the mass has heat the draft runs well. Mine is ice cold so it will take a day or so to get it warm. I have a cover that goes over the fire box when the wood is consumed and it seals the draft to maintain the heat in the mass. Restarting from that point is simple and strait forward. Really amazing having 900 degrees in the combustor and a stack temp of 70. It doesn't waste any heat.

Andrew Craig-Bennett
11-23-2011, 08:33 AM
Interesting stuff. Good luck.

Ian McColgin
11-23-2011, 09:02 AM
That is trescool. I helped a friend build a multi-downdraft unit that was more vertical - about ten tons of masonry and clay up the middle of a large old two-story farm house - but I'd not thought about the more practical smaller approach and I love the window seat sculpting. We need pix of a person recumbent with cat . . .

PAlien
11-23-2011, 03:31 PM
Is the exhaust going up your existing chimney? I believe you will need to exhaust horizontally, unless you have a very short exhaust path. Trying to exhaust a rocket stove vertically can lead to dangerous exhaust gasses collecting inside the dwelling, as well as corrosive condensate collecting and compromising the construction. As you've discovered, there's very little heat left to force the exhaust very high vertically. Good luck, I'll be excited to see your progress. Please keep us posted.

Tom M.
11-23-2011, 03:32 PM
I don't get it Mark. You are calling this, or something like it, a rocket stove? Where I'm from, a rocket stove is basically an insulated chimney that one cooks on top of. I built one the other day in two hours with coffee cans and soup cans.

http://www.npr.org/2011/02/09/133598036/engineers-hone-clean-energy-stoves-for-the-world

PAlien
11-23-2011, 03:45 PM
Tom, this version of a rocket stove is used to heat a space by transferring the heat to a large thermal mass for slower release into the space. Often referred to as Rocket Mass Heater or the like. It's still a rocket stove, just heats a cob bench or other thermal mass instead of a cook top, or sometimes, does both.

https://encrypted-tbn3.google.com/images?q=tbn:ANd9GcRRbVLFEQ1ADSVa3ikysna1YwPYwlqnu w91ox6A6prkI8iOdYWsoA

Mrleft8
11-23-2011, 03:54 PM
We used to call those "Russian ovens"......
A massive thermal sink with a fire box. The ones I have experience with took up to 4' logs. It took a good 2-3 days to get it up to temperature, but once it was there, it only needed a few small logs a day to maintain the heat mass. The one that worked the best was centrally located in the basement of the house, with ceramic tile floors that became toasty warm....

PAlien
11-23-2011, 04:01 PM
We used to call those "Russian ovens"......
A massive thermal sink with a fire box. The ones I have experience with took up to 4' logs. It took a good 2-3 days to get it up to temperature, but once it was there, it only needed a few small logs a day to maintain the heat mass. The one that worked the best was centrally located in the basement of the house, with ceramic tile floors that became toasty warm....

It's similar in theory, but the combustion is very different from a Russian oven or Masonry Heater. These burn a small amount of fuel completely and quickly, using the relatively new rocket stove technology.