#11  
Old 04-24-2009, 05:47 AM
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Default Re: Heat break?

Wow Drake. That's a lot of help--thanks.

Mark
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  #12  
Old 06-19-2009, 06:04 PM
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Default Re: Heat break?

Since you guys asked for it, I finally fired up my oven again.

Here is a picture of my landing with temp measurements on each side of the break. Inside oven floor temp 550+ and TC floor reading of 360 or so. Interestingly, taking various floor measurements there seems to be a 20-30deg avg drop across each brick as you read hot side to cool side.
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Heat break?-temps.jpg  
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  #13  
Old 06-19-2009, 06:50 PM
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Default Re: Heat break?

This forum is great!!

I love how you are all discussing the merits of the heat break at the opening. But, it kind of reminds me of when I went cross country bicycling.

I had read all sorts of things about touring bikes, how to reduce the weight, the skinny tires, etc. I loaded down my bike with my clothes, sleeping bag, 1 man tent, map, water bottle, and set off for Chicago.

On the first expansion joint I hit, on an interstate bridge across the river into Iowa, I popped my 'ultra light weight' racing tire inner tube in 2 places!

That day, I went and got a plain old heavy innertube, and a big fat plain old bicycle tire, and never worried about shaving off an ounce here and there ever again. In fact, loading down the bike made it kind of fun to ride -- a little more momentum up and down hills.

Yes, I realize this has NOTHING to do with pompeii ovens, or even pizza, but as all of you know, the perfection we strive for must always be tempered by the reality of the task... and I wanted to become a 'laborer'.

Lars.
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  #14  
Old 06-19-2009, 08:09 PM
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Default Re: Heat break?

Quote:
Originally Posted by Lars View Post

That day, I went and got a plain old heavy innertube, and a big fat plain old bicycle tire, and never worried about shaving off an ounce here and there ever again
Lars - you nailed it. I had road bikes, then mountain bikes. We recently bought a couple of beach cruisers - not looking back...
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  #15  
Old 06-20-2009, 11:22 PM
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Default Re: Heat break?

This is great! I am at the stage right now where I will start my entry arch and was going to put a 2mm piece of cardboard between the entry and vent which I would remove after.
My theory was that an air gap, be it ever so small would still act as a heat break and I think my entry arch will be strong enough to be self supporting without being keyed into the vent arch.
Am I going down the wrong path?
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  #16  
Old 06-21-2009, 09:20 AM
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Default Re: Heat break?

Rodney

IMHO I don't think it is worth the effort. There is so much mass in these ovens that properly insulated, they will retain heat longer than you really need.

The fire break I put into the floor was to keep my entry floor cooler, not to raise thermal efficiency. The amount of floor or entry arch in contact with the dome is very small compared to the area of the dome, so heat leakage is also small, probably in the area of insignificant.

As an example, after a good 2-3 hour pizza burn and another 2-3 hours for the temps to "settle" (brick face temp within 10 deg of center of brick temp) my oven looses 100deg a day (measured constant rate over 3 day period) with the door on.

Insulate your oven well and build a door instead.





Quote:
Originally Posted by Rodneyf View Post
This is great! I am at the stage right now where I will start my entry arch and was going to put a 2mm piece of cardboard between the entry and vent which I would remove after.
My theory was that an air gap, be it ever so small would still act as a heat break and I think my entry arch will be strong enough to be self supporting without being keyed into the vent arch.
Am I going down the wrong path?
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  #17  
Old 06-21-2009, 10:11 AM
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Default Re: Heat break?

I created a heat break at my entry by:

Bottom: a one inch wide ash slot, the width of the door, funneling down to a 4 inch circular opening in the structural slab.
Top: A three inch wide vent opening the width of the entry, funneling up to the flue.
Sides: A 2 1/2 thickness of insulating brick the height of the entry. This is the brick that kiln makers use - check with your local potters.

Last edited by Neil2; 06-21-2009 at 10:13 AM.
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  #18  
Old 06-22-2009, 12:11 AM
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Default Re: Heat break?

Cunfusing! I think I will go with no heat break as it sounds like there is no need and only 2 days each weekend to bake so there is no need to keep the oven hot past 2 days. Thanks for your help on this one.

My progress so far.
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  #19  
Old 07-02-2009, 07:59 AM
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Default Re: Heat break?

Mark,
I agree that the entry and entry floor is likely a significant source of heat loss. One consideration would be to use insulating firebricks when building the entry and entry floor. (see Pompeii oven instructions, pg. 62) I don't know if insulating firebricks are difficult to work with or would present other problems along the way. Maybe someone else has used them in the past. I chose to build my entry and entry floor from the regular fire bricks to keep the project as simple as possible.
Good Luck,
Steve Tidik
San Luis Obispo, CA
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  #20  
Old 07-02-2009, 03:34 PM
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Default Re: Heat break?

Wow, Wade! 100degrees/day loss sounds very efficient. I am about to pour my foundation slab so haven't gotten too far into this but had this idea: How about placing a 2-3" wide strip of insulating firebrick in the floor the width of the entryway? This could be placed where the vent meets the perimeter of the oven floor and also between the vent landing and the front of the oven where I plan to put an 11x38" piece of granite. Coincidentally, my piece of granite looks identical to yours, Wade. Would yours happen to be flamed?

John
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