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  #11  
Old 07-02-2014, 04:50 PM
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Question Re: To Thermal Break or not to Thermal Break? That is the question.

G'day
A 36/42in Pompeii is a large mass of brick. Once heated ( and insulated) stays hot for days and more heat than weekend sometimes. I haven't got a heat break and don't think its of real importance to a large oven.
However a smaller oven with a smaller mass I wouldn't mind betting even small savings like a heat break would have a bigger effect.
Just my 2 cents worth
Regards dave
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  #12  
Old 07-02-2014, 06:09 PM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

I put in a gap (no metal) all the way around, top, sides and bottom and notice about a 180 t0 200F degree difference. If i were to build another WFO again, which I am, I would probably do the same thing again. No scientific back-up, just my gut feeling.

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  #13  
Old 07-03-2014, 02:55 PM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

Thank you, this is some great information. It seems like the general consensus is that a thermal break is a worthwhile mod to incorporate into the build. It seems fairly straight forward, just leave a gap of 3/8 inch or so at the reveal where the arch and vent would normally be connected to the oven opening. This can be stuffed with gasket rope along the walls and arch (available readily from Amazon in 6' lengths), and the floor filled with a short length stainless square tube. Benefits are two fold. This will limit heat loss from the oven through the thermal mass of the throat, and reduce stress and cracking in the vent area due to expansion/contraction of the oven. Correct?
Thanks again!
-Jonathan
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  #14  
Old 07-03-2014, 03:28 PM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

I used rope, so a word of caution. The fibers come off a go airborne, so wear a mask. Then once you stuff the break, coat it with rigidizer or a homemade slurry of Portland/acrylic admix
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Old 07-03-2014, 10:30 PM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

Would stuffing the gap with a lean mixture of vermicucrete work?
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Old 07-04-2014, 03:31 AM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

I used S/S outside the inner dome and vermicrete around the rest of the break. A year on it seems to be fine.

The temp either side of the thermal break convinces me that it works. It is very significant and I am using it again for the oven I am building for my daughter.
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  #17  
Old 07-04-2014, 05:07 AM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

Quote:
Originally Posted by edsiajb View Post
Would stuffing the gap with a lean mixture of vermicucrete work?
Sure, but you still should either use metal or rigidizer because its friable.
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  #18  
Old 07-04-2014, 11:33 AM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

Since metal conducts heat WAY more than these bricks, is there a real benefit with filling the divide with metal. These bricks can absorb and retain heat pretty well, in regard to conduction, they are pretty poor. I have no doubt that the break will cause no harm (if constructed properly) but no one has posted empirical evidence that it helps. Any one with the break, please document the delta across the divide, with pictures so we can compare ( without the door on, that's just another variable) If the data supports the benefit, we should get it incorporated into the plans. Here is a test I did last week? https://www.youtube.com/watch?v=03Pwaf8NlOU
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Old 07-04-2014, 11:46 AM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

I plan to use a heat break in both my floor and between my oven arch and vent arch. I have limited experience w/this, so I only speak my opinion, having lots of experience w/concrete and masonry, just not brick ovens. I would not build one any other way. Besides the benefit of the heat breaks, to me, they also act as a control/expansion joint. They also open up design differences you would not usually have w/out them.
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Old 07-04-2014, 11:53 AM
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Default Re: To Thermal Break or not to Thermal Break? That is the question.

I meant to also add that I am not using any type of metal for a heat break. I have some ceramic fiber strip that I bought and will use that for a heat break on the floor, just outside of my hearth bricks. On the arches, I plan on using rope, as Stonecutter and others mentioned.
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