vent sizing

[jmargush]

I am getting close to closing in my 42" diam 20" tall dome and have started to think about vent construction. my opening is 20" wide and 12" tall at the center of the arch.

What size should my vent be? or how do I determine the correct size?

[david s]

For a 42" dial oven you need an 8" diam flue pipe. If making a brick chimney its internal cross sectional area should be at least the same as the 8" diam flue ie 50 sq in. Some funnelling to this will assist in smoke collection reducing the tendency for smoke to escape out the front, particularly at light up.

[v12spirit]

For a 42" dial oven you need an 8" diam flue pipe. If making a brick chimney its internal cross sectional area should be at least the same as the 8" diam flue ie 50 sq in. Some funnelling to this will assist in smoke collection reducing the tendency for smoke to escape out the front, particularly at light up.

The plans state that the chimney area should be 3-4 times the door height. Mine has a 15 cm high door (ridiculously small, 66 cm dome), that is 60 cm^2 maximum chimney area according to the plans. My chimney is 9.5 cm inner diameter, which has an area of 70 cm^2. That is more than the maximum chimney area required. However, my vent is a squirrel tail one and I can see my oven get smoky at start up and when I throw a big log of wood in it even when it is saturated. Will going wider with the chimney compensate for the aggressive horizontal part of the chimney or that will not make a difference and I am ok with the current chimney size? Am afraid going wider will make the oven less feul effecient, still don't want a smoky indoor oven.
Edit: The original plan incorporated an extractor fan but now I want the hoven naturally aspirated and self contained without any electrical assist.

[david s]

The plans state that the chimney area should be 3-4 times the door height. Mine has a 15 cm high door (ridiculously small, 66 cm dome), that is 60 cm^2 maximum chimney area according to the plans. My chimney is 9.5 cm inner diameter, which has an area of 70 cm^2. That is more than the maximum chimney area required. However, my vent is a squirrel tail one and I can see my oven get smoky at start up and when I throw a big log of wood in it even when it is saturated. Will going wider with the chimney compensate for the aggressive horizontal part of the chimney or that will not make a difference and I am ok with the current chimney size? Am afraid going wider will make the oven less feul effecient, still don't want a smoky indoor oven.
Edit: The original plan incorporated an extractor fan but now I want the hoven naturally aspirated and self contained without any electrical assist.

You can not take a one dimensional measurement like height and compare it with a two dimensional one (area)
You were warned about the potential smoke issues with your design when in the early stages, but you said you were installing an exhaust fan. That would be your best solution at this stage.
9.5 cm diam is too small for any oven. Mine oven is only 54 cm internal diameter yet has a 12.5 cm diam flue, that's getting close to double the area of yours. Anything smaller I'd consider inadequate. Regarding the horizontal section, anything flatter than a 45 degree slope will impede the draw.

[v12spirit]

You can not take a one dimensional measurement like height and compare it with a two dimensional one (area)

I agree with you. I was surprised too when I read this in the plans.



At the early stages I had an extractor fan and didn?t even think for a while that electricity may one day be going off for whiles as it is now. Pity.

[jmargush]

I just measured a clay flue liner that I am thinking of using and it has an interior area of 49 sq inches. Will this be large enough?

[david s]

That all depends on the size of your oven.
Check this post#2
A round 8" flue has a cross sectional area of around 49 sq in