Cracked hearth- Casa 2G 90

[d0rifto]

Hello,

I have owned the Casa2g 90 for about 6 month, and used the oven for about 15 times. I noticed the hearth had 2 long cracks and wanted to see how bad it was. I removed the tiles, which were heavy , but noticed that the cracks ran the backside of it.

Most people on the board say small cracks in the oven walls are normal, which I have but it hasn't caused any problems. Is this OK for the floor tiles?

I have my oven on a stainless steel stand with casters that moves back and forth about 30 feet. Basically from under the patio to outside, to clear the chimney and not cook dangerously under the patio cover. I dont think moving an oven would cause the tile to crack.

Also I noticed that the heat under the stainless plate, the metal gets quite hot. I wonder if the heat is leaking out? I am using the 2" insulation board supplied with the Casa2g oven.

The 2 images below are 1 side of the tile




This image is of the other tile that is cracked, but isnt as bad and doesnt run all the around the backside.

[d0rifto]

Re: Cracked hearth- Casa 2G 90

Bottom side of oven stand

[david s]

Re: Cracked hearth- Casa 2G 90

The larger any refractory pieces are the more inclined they are to crack, particularly floor sections.

[PIZZAMANMIKE]

Re: Cracked hearth- Casa 2G 90

I would assume you constructed you oven as light as you could since you move it around. It looks to me like you set the oven deck on the FB board only, can you provide me with more info on floor install.
Mike

[d0rifto]

Re: Cracked hearth- Casa 2G 90

"david s"- i guess i never thought about that. but doesnt some of the mobile wood fired ovens , such as The Fire Within, use Forno bravo ovens with multiple floor pieces? I remember seeing them at last years FB Expo.

"PIZZAMANMIKE"- The oven assembly consists of the stand and FB oven. I would say the stand is about 300 lbs. I used a mix of 304 stainless steel square tubing in various size, and stainless steel plate on top.

The insulation board sits on top of the stainless plate. Then the sand goes over the board, as mentioned in the FB install book. Next went the hearth cooking floor.

I welded 2" angle iron around the perimeter of the oven so it would not move around while being pushed.

How strong are the tiles from cracking? Any experience from Casa 2G owners?

[d0rifto]

Re: Cracked hearth- Casa 2G 90

Is there anybody from the FB staff that can give me any insight or recommendations?

[Tman1]

Re: Cracked hearth- Casa 2G 90

Is there anybody from the FB staff that can give me any insight or recommendations?

You should call them/ email them directly as I don't know if they check the board regularly.

The cracks don't look like anything I'd be worried about. Everything is relative though. What is big to one, is small to another.

[dmun]

Re: Cracked hearth- Casa 2G 90

I'm confused by your pictures. You took your oven apart to photograph the crack?

Also I noticed that the heat under the stainless plate, the metal gets quite hot. I wonder if the heat is leaking out? I am using the 2" insulation board supplied with the Casa2g oven.

Usually when an oven is leaking heat despite being properly insulated the culprit is wet insulation. It may be that your stainless base plate, being much more conductive of heat, may seem hotter, quicker than a conventional concrete support slab. All that heat has to go somewhere.

[james]

Re: Cracked hearth- Casa 2G 90

Hi d0rifto,

Sorry that you have a crack in one of your floor tiles. We have shipped many thousands of floor tiles and a thin crack like this is very rare. We have seen it only a couple of times. It turns out that 18"x18" is an optimal floor tile size for larger ovens, where there are few seams and very little hairline cracking. Cast monolithic floor are much more likely to crack.

Still -- you have a crack.

Looking at your floor piece, it does not appear that it is going to be a problem. It is not the source of any heat loss through the bottom of the oven, and when you place it back in the oven there is a very good chance that the floor pieces will never change and never be a problem. Of course if you have any problems with the piece, let us know. You can reach customer support on info at fornobravo.com, or 800 407-5119. That is the best way to get service.

On the heat under the oven, I think David's comment is right. There is an amount of heat working its way through the FB Board, and unlike concrete, the stainless steel is a very good conductor of heat. In the overall context of firing your oven, cooking performance and heat retention, the warm steel has very little impact.

Let us know how it goes, but basically -- keep cooking!

James

[d0rifto]

Re: Cracked hearth- Casa 2G 90

dmun- Yes, i took the oven tiles out of the oven. But I did not disassemble the 3 piece oven dome to remove it. It is not too difficult to do, especially since the outside of the oven isnt finished with any tiles, roof, other design. I just had to chip away at the FB mortar that was covering the front base, which was the insulation board, sand, then cooking tiles.

It has the scratch coat over the 3 layer of insulated blanket. Which I must add does a great job of keeping heat in, I do not feel any heat on the exterior of the oven. I just removed the sand then took the tiles out.

The oven tiles never had any cracks when I first used the oven and started to appear after cooking.

I would not be afraid of the cracks if it was only on one side, but 1 of the tiles has it running across the other side. Maybe ill post a video so people can see what it looks like, its kinda hard with pics.

Ill contact FB if it looks like it getting worse or if I need assistance!

[david s]

Re: Cracked hearth- Casa 2G 90

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]

Re: Cracked hearth- Casa 2G 90

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

[PIZZAMANMIKE]

Re: Cracked hearth- Casa 2G 90

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]

Re: Cracked hearth- Casa 2G 90

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]

Re: Cracked hearth- Casa 2G 90

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