Interesting flue concept from Germany - would that be permissible here?

[Tron]

A friend of mine in Germany is currently installing a wood-fired stove plus flue. He chose this system here, which includes an outside air kit, but draws fresh air from the top of the flue.
Is that kind of thing permissible in the US? I thought outside air always needed to come from the same elevation or from below, but never from above....

 

[stoveliker]

That would be correct for the US code indeed.

Is that a naturally aspirated wood stove he's installing?

 

[Tron]

Is that a naturally aspirated wood stove he's installing?

Yes, it is.

 

[stoveliker]

Well if both piping are fire rated, who cares which way the gases flow 🤣

 

[Tron]

Well if both piping are fire rated, who cares which way the gases flow 🤣

That's exactly what I don't get about this concept: how to prevent backdrafts.
The thing is that the whole stove and flue business in Germany is hugely overregulated. They banned older stoves for not being clean enough, and there is a government-appointed sweep that wields a lot of power and has to be used (and paid) for anything heating related. They can even shut down heating equipment.

Given that, I'm 100% sure they are aware of the backdraft issue but implemented a smart fix to avoid that. I just don't see it.

 

[stoveliker]

I know, and agree.

Maybe the fact that (i) it first goes down (it seems to go under the floor), then goes up on (ii) the cold (outside) side of a block flue (whereas the chimney is insulated it seems, yellow layer over the channel/tube), and then (iii) have a narrow path at the cap, will create enough impedance and cooldown of any warm gases trying to go up to not have the flow reversed?
After all less air has to come in than gas volume going out of the stove (though I don't know the combustion ratio, and thus whether that difference is signifcant or not), so a higher impedance going in will create a directional preference.

But I think the "first significantly down" is the biggest thing helping here.

 

[EatenByLimestone]

Looks like a good spot for a yellow jacket nest to grow large!

 

[Tron]

Looks like a good spot for a yellow jacket nest to grow large!

I looked at their homepage and they said they have drilled aluminum sheets in front of all openings. Not sure if that would deter wasps.
Here it is, in case you want to fire up Google Translate: https://www.schreyer-schornstein.de/schornsteinsysteme/fblask/

 

[EbS-P]

Aren’t there UL listed pellet or gas concentric intake and vent pipes

 

[EatenByLimestone]

My gas boiler had an option for the gas exhaust and intake in 1 tube. I think the intake was on the outside of the exhaust.

 

[stoveliker]

but gas and pellet are driven, so a fan directs the flow. No chance of backflowing smoke through the air inlet.
Big difference