#11  
Old 10-17-2011, 01:52 PM
brickie in oz's Avatar
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Default Re: First course

Quote:
Originally Posted by Omaharosario View Post
What kind of insulation & the what amount you would apply under the soldier course to fix this problem?
Also I want to understand why this creates a huge leak and why the insulation changes that? Not trying to question you just want to be a informed builder.
Thank you for your input it it very useful.
1" of calcium silicate board would help, 2" would be better.

Anything in contact with the oven itself will get hot and the heat will be transferred to what ever it touches. .
The more heat that leaks away the more wood you will need.
The entire oven should be cocooned in insulation, that way you will use less wood and have extended cooking time.
Done properly your oven should stay at cooking temps for days.

My last oven was near cold in the morning after a pizza party, my new one stays hot for a week and its all due to being properly insulated..

Quote:
Originally Posted by Omaharosario View Post
Thank you! How did you go about fixing yours??
I tore it down and rebuilt a new better insulated oven, it wasnt a chore for me because its what I do, bricklaying is a paid hobby for me.
But for someone who is only going to do 1 oven you may as well get it right to start with.
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Last edited by brickie in oz; 10-17-2011 at 02:07 PM. Reason: Fixing stutter.....
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  #12  
Old 10-17-2011, 02:03 PM
Faith In Virginia's Avatar
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Default Re: First course

I would use your 1'" fiber board under your solders. but your second issue is the 4" refractory cement that you plan to sandwich with your fiber board. If that 4" slab touches your soldiers then as you heat your oven you will also be heating that slab unnecessarily. so I would run the 1" insulation under and on the inside of those solders.

As far as why. the firebrick is dense and conducts (heat) energy very well. the concrete slab also conducts (heat) energy very well. if they touch each other the fire brick will transfer the (heat) energy to the concrete slab. The insulation layer will prevent that transfer of energy.
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  #13  
Old 10-17-2011, 02:49 PM
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Default Re: First course

It is not to late to tear it down and start over.
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  #14  
Old 10-17-2011, 03:31 PM
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Default Re: First course

Quote:
It is not to late to tear it down and start over
I had all of my soldiers mortared in and tore them out because I felt they didn't bond well. I ended up starting with a horizontal first course and just went up from there. It didn't take me very long at all and I am tickled I took the time to do it right.

Regarding the refractory slab sandwich - why? If you want extra thermal mass under the floor (I have 3.75" total in my floor), place ALL of your insulation under the floor. It will be much more efficient, IMHO.
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  #15  
Old 10-17-2011, 04:56 PM
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Default Re: First course

The best way to look at it is - your oven / dome should be "floating" on and surrounded in insulation. Anywhere the firebrick touches another hard surface (concrete slab, outside arch, countertops) - you will lose heat.

When you fire the oven - it's not just the floor and the top of the dome that gets hot. The bricks saturate with heat. When you saturate the bricks in the oven as you've built it so far - the heat will travel down the sides of the dome and begin to heat the concrete slab. The heat will continue to try to transfer to the concrete slab until it gets as hot as the firebrick.

Floating your dome on insulation prevents that heat transfer.
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  #16  
Old 10-17-2011, 05:15 PM
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Default Re: First course

I have been trying to track down your build post for a while now, that is looking like a brilliant oven! I have attached a sketch to illustrate what everyone here is talking about - you really want to 'cocoon' the whole oven in good insulation, it makes a HUGE difference to the performance of your oven as a whole.

Also, the refractory slab that you are going to pour, this is basically just a dry mixed refractory brick - when you pour this slab it will have very similar properties to the refractory brick floor (dense, fairly thermally conductive) so it will act as additional thermal mass under the floor. Is this what you were intending? 4" of additional thermal mass is significant, it will take a lot longer to heat up, but will also hold its heat for a long time (providing it's well insulated ) Unless I have the wrong end of the stick entirely and you've got your hands on a premixed insulating castable...
Attached Files
File Type: pdf Insulation Design.pdf (15.5 KB, 117 views)
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  #17  
Old 10-17-2011, 05:27 PM
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Default Re: First course

Although I agree with what everyone else is saying here, the important question I haven't seen asked here is what were you trying to achieve with your alternative design? It's pretty complex so I have to assume there was a certain goal in mind.

Your work looks really nice, take a step back and get this part right and you should end up with a great oven.
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  #18  
Old 10-17-2011, 05:33 PM
Peasant
 
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Default Re: First course

First I wanted to start by saying Thank You!
If the soldier course is floating on insulation board, does your soldier course get a good enough bond to the Refractory Castable Layer and each other to be structurally sound? Also I have already poured the Refractory Castable Layer. I have been talking with a gentlemen who has been involved with a couple of commercial oven in the area and this is where a lot of my ideas are coming from. Hope I did not go to far off the path, But I know the help from everyone will help me get there. Thanks again!!
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  #19  
Old 10-17-2011, 05:48 PM
benguilford's Avatar
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Default Re: First course

From your description the refractory castable layer is only bonded to the inside face of the solider course, and it really doesn't need to be bonded to the soldier course at all for your oven to be structurally sound - most of the ovens here on this forum cut the floor to fit inside the soldier course, which means the soldier course is self-supporting.

Do you have a layer of insulation under the refractory castable slab? If so, you could just lay your firebrick floor directly onto your refractory slab (with a thin layer of fireclay to level the floor bricks).

A sketch would help (I think I must be one of those darn 'visual learners' that my English teacher wife talks about)
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  #20  
Old 10-17-2011, 05:49 PM
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Default Re: First course

I think the refractory castable layer is what has us all thrown off. As you have it now it is doing little to nothing other then mayber stealing heat away from the oven and keeping it there. In commercial bread ovens they generally do something to increase the mass in the floor to retain heat for many loads of bread after one firing. The way you have this constructed won't even do that because it has insulation above and bellow. It's only contact to anything conductive is on the sides.

As for bonding to the castable layer, that's a moot point IMHO. The soldier and the castable will expand at different rates and the bond will probably be broken by themal expansion anyway.
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