About to start a corner build

[NCMan]

What's the purpose of insulating the chimney? I've seen and heard of that, but really don't get the intended purpose?

[Grahamstein]

Yes building a flue gallery reduced the exhaust by probably 50%. I also framed a chimney with cement board and filled it with perlcrete around a 24" flue pipe. I'll remove that China man's hat and top it with a stone eventually. The hat on there now seems kinda restrictive. Work has slowed a little but in still plugging along.

[JEFF88]

Grahamstein Did the flue gallery help with the soot? How do you like the oven?

[Grahamstein]

[Grahamstein]

it just wasn't sitting well with me so I went back and changed things. I got some insulating firebrick and some fireplace mortar and constructed a flue gallery of sorts. I didn't get pictures before I reinsulated but I snapped one from the inside. I think it should help considerably with drafting. It adds 9 inches in height but makes a much better transition rather than having the anchor plate just screwed on top of the arch like it was before.

[UtahBeehiver]

A lot of oven will get some soot staining on the outer arch area. I know that David S uses a nice glazed tile face with "black" mortar so it is easier to clean and the black mortar hides the soot stain.

[Grahamstein]

I had the same thought about arch heights being part of the issue as well. I forgot to measure the dome before starting my day 5 fire, but it looks to be about 16-17 inches. The inner arch measured 12, which seems to fall into that 2/3 range. The outer arch measured 13 inches high. So I think the combination of the arch heights and a slightly restrictive chimney are causing the exhaust to roll out the front. Is really only smoking when i put new wood in the oven, but I would say about 20% of the exhaust goes out the front instead of up the chimney. I may leave it, just because the only real problem it might cause is soot staining at the mouth. But I'm a little OCD so that will eat at me.

[JRPizza]

I checked out their web site to see what the geometry looked like but could not find exact numbers - I was wondering what the internal dome height and opening heights are, both for the inner arch and the outer arch. There might be something in their geometry that adds to the tendency to smoke. I also see from a UK site that the recommended chimney is listed at 300 mm od (11.8"), where my 8" double wall pipe is 10" od. Maybe your vendor sent you the wrong pipe and adapter?

http://www.orionheating.co.uk/cooker...a-oven-models/

[UtahBeehiver]

Clay flues are an option but they need to be insulated so they do not crack due to temperature differential between inside and outside. It is also possible that the CaSi absorbed some of the moisture from the vcrete layer possibly contributing to the smoking issue. This will dry out as the cure process continues. I would continue with the cure and see how the smoke is after the full cure, the ovens get better with each firing.

[Grahamstein]

Your correct about it being a Volta, and most likely therein lies the issue. Where forno bravo probably carefully examined what is appropriate for their ovens, the maker of mine probably said "fuck it, it's good enough". The flue pipe on mine measures only 18 inches in length. I'm thinking a longer pipe would help, but then I think if I'm going to start changing things, I might be better off if i just take that chimney off and just get 2 sections of 8x12 clay flue liner instead.

I think that's most likely the route I will take as I don't want the chimney getting to much higher.

[UtahBeehiver]

The 6" ID chimney is what was supplied with the Forno Volta (not a Forno Bravo product)? The Forno Bravo e- plans call out 6" for 32 and 36 inch ID ovens and 8" for 40 inch and larger. I would continue to cure and see if the smoking diminishes.As mentioned start a draft fire under the chimney opening first. I originally had a 3 foot stack but had to add an 1 footer to get a better draw.

[Grahamstein]

Its a 40" oven, the kit came with a 6" chimney.

[UtahBeehiver]

What is the ID of the oven and the ID size of the chimney? New ovens are notorious for smoking. Once cured, I normally start a small "top down" burn under the chimney opening to get a draft going then push the fire into the dome once the draft is going.

[Grahamstein]

Ive been successfully fighting the urge to make the fires too big too fast. I just don't know if its appropriate to take a step back and do some more insulating. One other concern i have is that my chimney may be too small, as there seems to be a decent (AKA too much) smoke coming out of the mouth of the oven. I dont know what would be the most advisable step at this point, take the insulation off and fabricate a larger chimney? Add more height to the flue for better drafting? Try a less restrictive cap?

[UtahBeehiver]

This is the point where we see builders wanting to hurry the cure process and fire too hot too fast. It is unknown how much water remains in the factory casting and by going to fast to hot you run the risk of cracking the dome.Take it easy, you can aways do some dutch oven cooking while you cure. Looks like you have some great helpers.