Heat Break

[brickie in oz]

To break or not to break, that is the question.

Or it was until I did it on the new oven..

The fire embers inside have been soaking for about 2 hours and the oven is 400c.
The pics below are self explanatory.

I used insulating fire bricks between the oven and outer skin on the front only and in the flue below the damper, the damper is also insulating fire bricks.

There is a ceramic rope in between the heath and the granite tiles.

The build, http://www.fornobravo.com/forum/f44/...two-15241.html (Oven number two..)

Hearth (by the door), 130c.
Granite, 115c.

Fire Brick, 223c.
Insulating Brick, 93c.

[ThermoJax]

Well done !! A great proof of concept.

[Tman1]

Awesome info!

[Les]

Originally Posted by ThermoJax

Well done !! A great proof of concept.

Is this really needed?? The brick doesn't conduct heat all that well. In regard to the flue, I would think that the hotter the better for draft. You got me curious though. Next time I get to temp I want to see the delta between the interior floor and a few inches away on the landing.

[david s]

There are three advantages in having an insulated gap.
1. Reduction in heat conduction and consequent heat loss.
2. The expansion joint reduces or eliminates any outward pressure on the exterior arch.
3. Reduces the temp. differential between the inner and outer surfaces of the outer arch thus reducing thermal expansion stresses.
Hands up those who have cracks in their outer arches. I bet you don't have a thermal break.

[Lburou]

I'm planning an arch of insulated firebrick (IFB) just outside my inner arch. Then, an air gap between the brick landing floor and the granite in the front two thirds of the oven landing. I've placed rigid insulation between the firebrick at the front of the oven landing and the support for the granite landing (attachments one and two). The air gap between the firebrick and granite will be less than one sixteenth of an inch (to be filled with ash).

Will study incorporating IFB in the chimney structure Brickie...Great 'Demonstration/Validation' phase! What I'm not clear about is your IFB placement and how you protect the inside edge of the IFB as you run a peel through there......? In other words, is the inside IFB edge out in the open? I'm working on that issue.

[Les]

Originally Posted by david s

Hands up those who have cracks in their outer arches. I bet you don't have a thermal break.

I just checked an I have zero cracks at that location. Maybe I am lucky. I did notice a crack on one of my porcelain tiles, but that was from freezing, about 4 foot from the entry.

[Lburou]

My goal in using a heat break is to maximize heat retention (read minimize heat loss) for extended baking, after the pizza bake. There is one other issue. That is the hot summers in Texas. The heat break, and less radiated heat from the landing, should make it a little more tolerable while standing in front of the hot oven in the heat of summer........I know, I live in my own dream world

Goal is not to minimize cracks, I already have cracks and haven't fired the oven yet

[brickie in oz]

Originally Posted by Lburou

What I'm not clear about is your IFB placement and how you protect the inside edge of the IFB as you run a peel through there......? In other words, is the inside IFB edge out in the open? I'm working on that issue.

You can see the insulating halves in the dry set out I did before I built the oven.

[brickie in oz]

Tonight's effort.
Ambient, 21c
Granite, 55c
Hearth, 120c
Fire Brick, rebate (near the entry) 300c
Insulators ,(near the entry) 150c

Oven, 700c

Back of the ceramic blanket that surrounds the oven, 27c

Front entry arch 30c

The last oven was too hot to touch at times, this one isnt.