Combo

[nhans]

Back again fellas. I’m still trying to figure out how to have pizza oven fireplace combo. I just poured the top slab and ready to set pizza oven on top in about 1 week. Starting to get cold here in Maryland.

Can someone explain whats the reason a fireplace can’t be vented out the back?

I have an anticipated finished area of approximately 34 w x 24h x 40 d beneath the oven. I really want the fireplace beneath the oven and hoped to find a solution. The only place I can vent to is behind the structure.

I thought I could do a Rumsford design type by going shallow - maybe 24” to middle of the box. Then make a tupe of wind tunnel that tapers left and right and top and bottom to 8” hole at back / top of box. Does that make sense?

The ceiling would taper back 2” front to back.

The walls would taper to back, but remember, only to middle of box because it will be shallow. The Back wall of fireplace would only go up approx 18” then taper backwards and up.

So side wall slant inward, ceiling and top of fireplace slant up to connect with 8x8 hole for venting out the back.

My thought is there should be a natural current from wide mouth face to back/ middle / top ............ tapering hole.

Sorry for the bother but would really try to make it work.

Thanks in advance for any explanation.

[nhans]

[nhans]

[Gulf]

Can someone explain whats the reason a fireplace can’t be vented out the back?

I don't like the term "can't". Will it be efficient? I doubt it. Can you make it work? Maybe. Preheating a flue or chimney helps a lot with getting a draw started even in the most difficult situations. That said, I think you have the "cart before the horse". Your design (if I understand it correctly) would have been much easier to have been built before the oven's hearth was in place.

[MarkJerling]

Like Gulf says, I don't think it's a case of "can't" but more a case of - "How well will it work?" Superimposing a few different flue options onto my pizza oven drawings, I think it can be done, but what i can't say is how well either option would draw. In each case, I've assumed that the flue would go up missing the outside of the pizza oven dome, but need not be all the way back from the rectangular base. (With other words, taking the flue up on one of the two rear quadrants.

In each case, I've assumed a 110mm x 400mm throat and a 200mm diameter flue. The question that remains hard to answer is: How well will the low slope 'horizonal' flue draw? I would guess, not too badly, provided there's reasonable height to the flue overall.

[david s]

Only way to find out is to build it, but a horizontal flue is a design no no and a recipe for lots of smoke out the front.

[MarkJerling]

Only way to find out is to build it, but a horizontal flue is a design no no and a recipe for lots of smoke out the front.

I'm also quite concerned that the horizontal flue will soot up quite badly. Some books I have on old fireplaces say that the flue should not deviate more than 45 degrees from vertical. In fact, most seem to indicate that more than 30 degrees from vertical is not advisable. But, I know that my pizza oven flue works, so clearly quite "flat" designs can work, so I think you have two choices. Build it and trial it, or build a mock-up and try that.

I would think the left and centre designs (per my sketches above) should draw ok, but I'd worry about the right hand one smoking out the front. Of course, the right hand one will be the easiest to sweep, so there is that!