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Well, I got very inspired by this idea some years ago. This autumn I wanted to realize the idea. Now, 4 rebuilds later, I can conclude with a simple answer: The riser is by far high enough to create the needed draft. With a simple bathroom ventilator, drawing 90 m3/hour everything works just fine. And I suspect all my previous builds might have worked just as fine this this kind of draft.

Well, after all rebuilds and your polite thoughts, it seems there is really only one simple answer: Draft. Im stubborn, but now Im slowly gain the knowledge too. With a simple bathroom ventilator, drawing 90 m3/hour everything is fine. And I suspect all my builds might have worked just as fine this this kind of draft.
So, actually I could tear down the whole construction; I suppose the riser has no function in front of the ventilator?
And I could be back with the beautiful batchbox...

Yes, you are right Glenn. The insulated chimney would help.
Allthough it is purely mafiosic regulations ;-(
But you know, with a regular chimney fire you would like to have it over the houseroof.

Tobias: Length of the horizontal run is about 27 feet.
I tend to agree with you, too much is against this construction.
Exittube is about 30 degree celcius with outside temp at zero.
You are not hijacking anything, Im very happy for all contributions!

Glenn: Yes, because of the two storage building, the chimney must be 5 meter high, and dobble insutaled is a must. So there are good reasons to find other solulions

Ianto, ok, I think I get it now. Next time I try, I will make a 6 feet riser and a biiiiiiig voluminous bell.

Kurt: Ok, ofcourse, dobble barrel A very smart thing. From a thermal point of wiev, the bigger the better. Like in ancient thermal baths, which were heated beneath the flors and through the walls. But still no experience showed me any power produces through the barrels. As Hans also confirms, the barrel is an obstackle. But with dobble barrel the gasses have more time to get rid of the heat and therefore can flow out beneath with the least resistance.

Hans: "...draft has to be coming from somewhere" Its difficult to get a good picture; but after 5-10 minutes burn, I see the draft working correctly beneath and flames building higher up the sticks starting to point upwards at the same time. So some air is getting sucked down and some just enters and then is hauled upwards without getting into the riser. This just worsens until the draft stops. It becomes an open fire on top of the feed. Air is sucked in from outside, not downwards through the hot riser.

Now I just tryed with a short chimney. It works better, so its obvious, that the J-feed needs more draft, than my system delivers.  Offcourse it would be sad to let go of the self feeding. But ericting a 5 meter high dobble insulated steel chimney, as would be required here, doesnt feel good. Maybe a fan would be a way out?


Im still wondering: Where are the people, who advocate J-feed and horizontal outlet? I really would like to see their systems running!

Kurt: What is a dobble barrel heatriser?

Tobias:
- Cost is a point here. Chimney starts where your stove ends. Thats an extra, which doesnt give any heat bonus.
- Estetics yes.
- Without chimney you break with old stiffened ways of thinking.
- With a chimney you must manually stop the draft, when the stove cools down, to prevent loosing all gained warmth.
- Only a chimney can catch a chimneyfire. A horizontal piping will never be able to perform like a heatriser.

Hans:
"(1) it acts as a trap to prevent the cold air in the horizontal run from flowing into the heat rizer making the system run backwards."
Did you experience this, or is it a thought? From my experience the warmth from the heat riser gently pushes the colder gasses out the horizontal flue, keeping the right direction all the time.
"(2) After the smoke stops burning in the heat rizer it starts to cool and becomes heavier and wants to fall."
Yes there is a temperature fall from heatriser to the exit of drum. And yet: did you ever fire your system without drum? The gasses leave strait into the heavens. Apperently there is no such thing as "wanting to fall" in the drum. The gasses have to be pushed downwards, through it. The drum is an obstackle, creating resistence in the system, that has to be overcome by the force of the heatriser.
Thats the reason I have all tubing (exept the exit) horizontal, in order to have no resistance occuring from temperature variations.
I didnt experience flow back at any moment. Also wind is of no concern in this area.
The exit is pointed downward to avoid cold air to creap in and cool down the system, when not operated.

I definitly will try the system with some few meters of chimney, to see, if it will overcome the fire creaping up the feed. Allthough I have little hope with the soft wood.
Instead I suppose I will have to leave the J-tube for a L-tube, for which there might be enough draft.

Glenn: You bring in some valuable information about existing horizontal systems. Thank you!
Yes, you might be right, that the system could benefit from a higher riser. And yes, like also
Tobias proposes, I will try a chimney.

There is no bell here. Only free flow through the ducts. And at least what comes out during good burn the first few minutes, is slow flowing moist 40 degree celcius.

Tobias and Hans:
Im sure that a higher heatriser, which Hans surgest, would improve draft.
But how would a drum/bend down increase draft?
Im inclined to think, that the hot gasses look for a way upwards?

Thank you Tobias
Riser is 60cm effective, 90cm from buttom of burnchamber to the top of the horizontal tubing.
Riser is square 6x6"
Feed is 5x6" and 9" deep
Tunnel is 5" between feed and riser
Now I added a picture from the recent build with a more clear J-tube.
Well, after a short time fire creeps up the sticks...

Glenn: Do you mean to say that this system would function if it was placed indoor?
I mean, somebody made functioning horizontal systems, didnt they?
Did you run horizontal systems?