Hardi backer board usage - question...

[67shelby]

Does anyone have a finished oven using the Hardi backer board? I'm having some problems and wondered if anyone else is experiencing anything similar.

So far, from what I have experienced, you should be very careful with the placement of your elements next to the backer board. I guess I was naive and thought I could just put my elements in like I've seen others do with metal and the backer board is just being roasted. I'll take some pictures, but so far, I've pretty much roasted the backer board and it is starting to crumble. I'm using two elements, one 2700 watts one 3400 watts and the 3400 watt element has almost baked the backer board into dust. The 2700 watt element has a distinctive char pattern in the shape of the element.

My second attempt was to put sections from the oven I used above the element and it helped, but not enough. I'm going to remove the section where the elements are and replace it with sheet metal with a gap.

I still have some concerns that the cement board will absorb the heat since I have been also having problems even coming close to 400 degrees with an oven 3 ft x 3 ft x 6 ft.

Did I just get ahead of myself and not do enough research?

Thanks for the help. The board has given me plenty of info. Maybe I just missed this.

[raydog]

I use backer board for my commerical oven and no problems, but I use torpedo kerosene heaters for my heat source. My oven size is 10' long x 7' high x 5' wide, and insulated witjh commerical grade rock wool, I've been using this system, now for over 7 yrs.

[67shelby]

Originally Posted by raydog

I use backer board for my commerical oven and no problems, but I use torpedo kerosene heaters for my heat source. My oven size is 10' long x 7' high x 5' wide, and insulated witjh commerical grade rock wool, I've been using this system, now for over 7 yrs.

How does your heat come into the oven? Does it directly hit the backer board?

[67shelby]

Here is a pic. This is after trying to warm the oven for 1/2 hour, then adding a porcelin piece above each burner and trying again for 1/2 hour.

http://www.lornewillard.com/images/P...n/DSC08397.JPG

As you can see, it got pretty hot.

You can see what it did to the insulation (not a great pic, but you can see it got the insulation pretty hot too):

http://www.lornewillard.com/images/P...n/DSC08408.JPG

I mounted it like it was in the oven, using the original hanger.

http://www.lornewillard.com/images/P...n/DSC08404.JPG

The other side was not as hot because of less wattage:

http://www.lornewillard.com/images/P...n/DSC08399.JPG

So the insulation wasn't quite as bad.

http://www.lornewillard.com/images/P...n/DSC08407.JPG

[Banditperformance]

Are those elements on the roof I havn't fired my oven to full temp yet, waiting on door pueces first, but I lined a sheet of Aluminum between the Hardi and the elements on mine. Also, that hardi looks different from my stuff. Mine is 1/2" and doesn't have the gridwork lines. That's the 1/4" stuff you have, right? not sure, but that might be a difference.

[67shelby]

Yea, I put them on top. Is that going to make a big difference?

I just added a 20 gauge piece of sheet metal offset 2 1/2 inches and it made a bunch of difference. I did use the 1/4 backer board, and with the new offset sheetmetal, I added another layer to make it 1/2 inch. My first test was to burn off the oil on the sheet metal, but it ran to 150 degrees pretty quickly. I'll test it more later today.

You might do some testing, but I would offset it. I think the difference to the kerosene heat is that it isn't as hot at the source like an element.

[Banditperformance]

Ya, that will make a huge difference. Heat rises. You might have upwards of 50-75 or more degrees difference between floor and celing temp. And depending on where your temp sensor is, the oven may have hige temperature gradients(not good) The elements should be at the bottom, so they heat the air,then the hot air rises, and cooler air comes down in contact to the element. Natural convection/air movement. Mine are bottom, mounted on the sides, spaced out 1" from the wall. Most all mount them on the bottom or lower sides. And space them from the wall. Were yours right against the hardi?

[67shelby]

Yes, against the board. Even with a porcelien piece (cut from the old oven)between the burner and the backer it still got too hot.

I'll see if I can move them to the bottom.

[Banditperformance]

I'll get some pics today of how I mounted my elements.

[67shelby]

Originally Posted by 67shelby

I'll see if I can move them to the bottom.

Thanks in advance for the pics. Somebody suggested I just turn the oven upside down and you know, that will work!!! I've got to get through the first few days of the year at work, so maybe this weekend...