Author Topic: clay oven heated by gas inside and underneath the floor  (Read 772 times)

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Offline jamieg

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clay oven heated by gas inside and underneath the floor
« on: March 16, 2015, 04:36:04 PM »
Hi,

I am in the process of designing/making a clay oven.

It is a clay oven - powered by gas.

After years of headaches as a result of losing heat on the floor during peak hours - I am going to have a gas burner inside the oven and ALSO - a gas burner under the floor. I am curious as to why I have never seen this done.

Can anybody point me to a resource illustrating how to implement a gas burner underneath a clay oven with a brick floor?

Thanks in advance,

jamie


Offline TXCraig1

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Re: clay oven heated by gas inside and underneath the floor
« Reply #1 on: March 16, 2015, 04:59:22 PM »
After years of headaches as a result of losing heat on the floor during peak hours - I am going to have a gas burner inside the oven and ALSO - a gas burner under the floor. I am curious as to why I have never seen this done.

2-Stone, Blackstone...
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

Offline jamieg

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Re: clay oven heated by gas inside and underneath the floor
« Reply #2 on: March 16, 2015, 05:51:15 PM »
True... but why is under floor heating confined to bbq style ovens that cook one pizza at a time?

Why is this not standard practice in a commercial environment where there is likely to be an issue with losing floor heat during peak times?

Any guesses?

:-)

Offline TXCraig1

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Re: clay oven heated by gas inside and underneath the floor
« Reply #3 on: March 16, 2015, 07:35:23 PM »
Real ovens have enough mass in the deck that they don't need it.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

Offline shuboyje

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Re: clay oven heated by gas inside and underneath the floor
« Reply #4 on: March 16, 2015, 07:50:48 PM »
I agree with Craig, a well designed oven that is suited to the pizza style it is cooking will not have this issue.  It's not rocket science, the heat put in by the fire has to match the heat taken by the pizza.  The challenge is knowing what it will take to achieve that with the style pizza you are after.  Outside of fast baked neapolitan there isn't really a baseline to go by.

IF you decided to proceed with a two burner oven, I would personally isolate the burners from each other to ensure the lower burner does not starve the upper burner for oxygen.  Build an insulated cavity bellow the floor with it's own air supply and flue connection that does not connect to the oven cavity in any way. Do the same with the upper burner in the oven cavity.  Again two separate flues would be the simple method.  You might get away with tapping the two into a common flue, but could potentially end up with it drawing backwards through one of the inlets which would lead to smoke in the kitchen.
-Jeff

Offline vtsteve

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Re: clay oven heated by gas inside and underneath the floor
« Reply #5 on: March 16, 2015, 10:05:28 PM »
Real ovens have enough mass in the deck that they don't need it.

...and enough insulation to retain it.
In grams we trust. :)

Offline TXCraig1

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"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

Offline vtsteve

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Re: clay oven heated by gas inside and underneath the floor
« Reply #7 on: March 16, 2015, 10:28:20 PM »
 :-D
In grams we trust. :)

Offline jamieg

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Re: clay oven heated by gas inside and underneath the floor
« Reply #8 on: March 17, 2015, 10:31:53 PM »
Real ovens have enough mass in the deck that they don't need it.

Apologies for my ignorance... by mass... do you mean floor space? Are you saying, there is always x% of floor space not in use... so as to always have at least a % of the floor re-heating?
« Last Edit: March 17, 2015, 10:41:46 PM by jamieg »


Offline jamieg

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Re: clay oven heated by gas inside and underneath the floor
« Reply #9 on: March 17, 2015, 10:40:42 PM »
@shuboyje... I am cooking hybrid new york/neapolitan pizzas... 3 min cooking time... the oven works very well before and after high peaks times... during peaks times - the air temp drops a bit... but the floor temp drops significantly...

Offline TXCraig1

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Re: clay oven heated by gas inside and underneath the floor
« Reply #10 on: March 17, 2015, 10:45:19 PM »
Apologies for my ignorance... by mass... do you mean floor space? Are you saying, there is always x% of floor space not in use... so as to always have at least a % of the floor re-heating?

No - mass - weight - a large volume of material such as refractory, brick, steel, etc. below the floor that can store large amounts of heat so that the temperature on the floor doesn't drop after you cook a pie.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

Offline jamieg

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Re: clay oven heated by gas inside and underneath the floor
« Reply #11 on: March 17, 2015, 11:05:08 PM »
Thank you Craig.

At the moment, we cook on a single layer of refractory bricks (2cm in height). Below them are another layer of very thick bricks (i am not exactly sure what they are) which were part of the old floor, but never heated up very well.

To test your theory, presumably placing another layer of the same refractory bricks I currrently use to cook the pizza... immediately underneath this layer would noticably improve the heat retention? Or is there something even better I could do?

:-)

Offline TXCraig1

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Re: clay oven heated by gas inside and underneath the floor
« Reply #12 on: March 17, 2015, 11:09:36 PM »
Thank you Craig.

At the moment, we cook on a single layer of refractory bricks (2cm in height). Below them are another layer of very thick bricks (i am not exactly sure what they are) which were part of the old floor, but never heated up very well.

To test your theory, presumably placing another layer of the same refractory bricks I currrently use to cook the pizza... immediately underneath this layer would noticably improve the heat retention? Or is there something even better I could do?

:-)

I think they would have to be mortared together so that you would have efficient heat transfer in and out. If not, you will likely have an air gap that will have an insulative effect.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

Offline jamieg

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Re: clay oven heated by gas inside and underneath the floor
« Reply #13 on: March 17, 2015, 11:14:31 PM »
Presumably, I would use refractory cement to do this?

Would 2 layers of refractory bricks (2cm thickness each brick) be a respectable mass? Or should I go more?

Thank you again!!

Offline TXCraig1

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Re: clay oven heated by gas inside and underneath the floor
« Reply #14 on: March 17, 2015, 11:19:31 PM »
Presumably, I would use refractory cement to do this?

Would 2 layers of refractory bricks (2cm thickness each brick) be a respectable mass? Or should I go more?

Thank you again!!

I'm not really the one to ask. I'd PM Tscarborough and Stonecutter if they don't chime in here. They can both tell you exactly what to do.
"We make great pizza, with sourdough when we can, commercial yeast when we must, but always great pizza."
Craig's Neapolitan Garage

Offline jamieg

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Re: clay oven heated by gas inside and underneath the floor
« Reply #15 on: March 18, 2015, 01:07:11 AM »
Cool, I have sent them a pm... hopefully they will report back here... :-)

Thanks everyone.

Online Tscarborough

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Re: clay oven heated by gas inside and underneath the floor
« Reply #16 on: March 18, 2015, 07:37:23 AM »
Layers of mass are not a good solution for the reason noted above (incomplete bonding).  Better to remove the 2 layers you have and replace them with one layer that has sufficient mass to get you through peak times, probably 12cm.  If you have no issue with the oven at off peak times I would not mess with more burners, etc., your problem is not in getting enough heat into the mass, it is with having enough mass to handle peak heat transfer out of your floor.


Offline JD

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Re: clay oven heated by gas inside and underneath the floor
« Reply #17 on: March 18, 2015, 08:18:42 AM »
At the moment, we cook on a single layer of refractory bricks (2cm in height). Below them are another layer of very thick bricks (i am not exactly sure what they are) which were part of the old floor, but never heated up very well.

Maybe you just need to remove the thin layer of refractory bricks and really allow the original floor fully heat up. You may not need to do any major work at all.

Offline jamieg

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Re: clay oven heated by gas inside and underneath the floor
« Reply #18 on: March 20, 2015, 07:40:20 AM »
So, I have just noticed another oversight in my existing oven. There is no floor insulation! If I put my hand underneath the oven - it is boiling hot. I had only ever thought previously about the insulation on the sides and top of the oven which is actually very good. So, I will add some insulating bricks below the oven floor and see how much of an effect this has.

I think, fixing this problem, while also ensuring a good mas of refractory brick on the floor and an oven big enough so that the floor gets a rest occasionally - will give me what i need.

A final question... is there a post regarding the A-Z process of making a clay oven - which stands above all other posts? - much like Craig's Neapolitan Garage has become comprehensive?

Thank you again,

jamie


 

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