Cracked hearth- Casa 2G 90

[david s]

The thermal conductivity of different materials shows some surprising results. Stainless steel is about 4 times less conductive than mild steel and copper is about 25 times more conductive than the stainless. My first oven had a small black rock set into the outer shell and although the outer shell was only warm when the oven was ready you couldn't hold your hand against the dense rock. It became our temp guage.

[david s]

Should also have added that the stainless is about 10 times more conductive than concrete.
Check out Thermal Conductivity of some common Materials

[PIZZAMANMIKE]

In researching your floor and installation, I beleive in the installation guide ( pgs 10 thru 13)It Calls for 3 1/2" of concrete, I believe the floor is cracking do to not enough thermal mass to collect the heat, only my 2 cents. If you installed it corectly you should not have any issues as I am still using FB ovens I purchased 7 or 8 years ago.

[d0rifto]

Instead of adding 3.5" of concrete, wouldn't it be better to add another 1" or 2" insulation board to the bottom. Look at the new FB Premio ovens, they use 3" insulation at the bottom.

Are the FB insulation boards there to absorb heat so the concrete base does not get too hot?

Or is it there push the heat back into the tiles?

If so then I could use insulating firebrick, rather than typical firebrick, sandwiched in between the insulation board and cooking floor. I was thinking this would be easier to add more insulation without having to take apart the oven walls

I believe the exterior of my oven works well because it calls for 3 inches of blanket and I do not feel any heat when I put my hands on it. The layer of my scratch coat is less than 1” thick also.

"PIZZAMANMIKE"- "I believe the floor is cracking do to not enough thermal mass to collect the heat, only my 2 cents"

So the floor is cracking because heat is being wasted? If it is being wasted that means the cooking floor is too cold, which it is and I cannot get it past 600+F. Wouldn’t a cooler cooking floor mean less chances of cracks then?

[james]

Hi guys,

This seems to be taking on a life of its own, and there is a lot of incorrect information here.

There is nothing wrong with the insulation, the floor tile, or the fact that the oven is installed on a steel plate rather than concrete. As long as the tray that holds the oven is rigid and does not wobble in any way, it is fine. Though if there is a wobble, that would put pressure on the floor tile.

Think of it this way. We have installed 10,000+ floor tiles in the FB manufactured ovens, and fewer than 5 pieces have developed a hairline crack. That is .05%. Plus, the don't wear out.

It is also important to point out that the firebrick tile floor is much better than a cast floor. The firebrick tiles are compressed and kiln fired, and they cook better and last much longer. We have somehow taken a big positive, and made it sound negative. :-)

James