Author Topic: Want to build a gas fired deck oven. Any plans available and suggestions?  (Read 25977 times)

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buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #120 on: August 26, 2012, 11:19:38 AM »
Richard, That's the purpose of the thermo sensor. When the oven reaches a certain air temp the sensor sends a message to the solenoid in the control box to shut off the gas to the burners. When the temp drops the reverse happens and the solenoid opens, gas flows and in your case the piezo igniters light the burner and the process repeats itself.
Don


Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #121 on: August 26, 2012, 12:02:09 PM »
Quick reply there Don. 

I didn't make my question very clear.  What I mean to ask is: Is there any way of regulating the top temperature which is independent of the bottom temperature.   Or to put it another way, is there only one thermometer in a typical deck oven, i.e. the upper and lower temperatures cannot be controlled separately.

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #122 on: August 26, 2012, 01:34:40 PM »
Richard, That would require two seperate control boxes and sensors for upper and lower, but you don't need that because you're not baking below the hearth. My sensor is right at the top of my oven as most ovens are. I think you're trying to make this more complex than really is. A simple system will give less problems over time. If you had an electric oven, then yes, you might have two seperate controls for the upper and lower heating elements. Are you planning to have upper and lower gas burners?
Don


Quick reply there Don. 

I didn't make my question very clear.  What I mean to ask is: Is there any way of regulating the top temperature which is independent of the bottom temperature.   Or to put it another way, is there only one thermometer in a typical deck oven, i.e. the upper and lower temperatures cannot be controlled separately.

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #123 on: August 26, 2012, 11:22:07 PM »
Are you planning to have upper and lower gas burners?
Don

No one will like this answer but I'm still not decided!   The extra complications in build would be offset buy the fact that everyone here can relate to the concept of 2 independently controlled burners.  

There is the problem that there is more stuff that can go wrong in the future.  However without some way of separately controlling upper and lower heat it seams that that getting an even cook is a bit chancy.  If I have too much stored heat on the ceiling or the ceiling is too close to the deck then I will consistently have over browned tops.  Conversely, the opposite could also be the case.

The main disadvantage that I see with a top burner is the requirement to make the gap between the ceiling and the hearth wider.  About 2" wider should be enough.  I want about 9" of work space so that would make the gap come to 11".

I would say that overall I am leaning towards incorporating a top burner.  Having said that some mornings I wake up chastising myself for trying to reinvent the wheel and determioned to make do with one burner! :-\

On the aluminium  plate question.   Would this be considered, what you guys call "the deflector".  Is 6mm thick enough to avoid warping.   Is $100 going to be an unnecessarily expense?  Should I make it $200?

Thanks for your thoughts.
  
« Last Edit: August 26, 2012, 11:24:39 PM by Sqid »

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #124 on: August 27, 2012, 08:14:30 AM »
Richard, I forgot to mention conveyor pizza ovens use upper and lower burners with seperate controls not just electric ovens. I wouldn't have a clue what the interaction would be with a deck oven with both upper and lower burners besides trial and error but I know there has to be an interaction between two sources of heat and a hearth.
Don

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #125 on: August 27, 2012, 11:32:50 AM »
A conveyor oven would be loosing so much heat, being open on two ends, that two burners must be essential.

I envisage the upper burner on my oven to only kick in occasionally when the door has been open for a long time.  Maybe only use about 30,000 btu and keep 120,000 btu below.

Shuboyje mentioned that a manual control would be suitable for the upper burner.   I think I shall probably wire it in to a separate automatic thermostat controller.  Also I think I shall be using a normal thermostat rather than a PID as the work load on the oven is so variable.

Offline Chicago Bob

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #126 on: August 27, 2012, 12:33:16 PM »
"Also I think I shall be using a normal thermostat rather than a PID as the work load on the oven is so variable."

Is that not the advantage of the PID....able to better control variable situations?  Hmmmm......
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Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #127 on: August 27, 2012, 11:12:44 PM »
Hi Bob

My understanding is that a PID uses fuzzy logic to learn from past experience what to tell the burner to do in order maintain a constant temperature.

This is great for heating when the parameters are relatively constant i.e. different times have fairly regular ambient temperatures and fairly regular demands for heat.

With an oven.  We are generally in need of more burner activity at supper time which a PID would learn and be able to burn the gas accordingly.  Occasionally the oven sits there doing nothing for 2 hours and at 3.50 pm is called on to cook 25 pies.  I don't think a PID would cope so well in this situation.

I think the above would just about fit on the back of a postage stamp!    

Offline Chicago Bob

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #128 on: August 27, 2012, 11:35:18 PM »
Oh OK Squid, thanks.
I thought the PID was more sensitive to changes and can react faster than a normal thermostat.
btw, what does..."I think the above would just about fit on the back of a postage stamp! "  mean?
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Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #129 on: August 27, 2012, 11:49:47 PM »
Your correct in that a PID can keep a temperature more constantly adjusted.   It doesn't exactly react faster but it does predict what will happen.  For instance a thermostat would turn on the burner at 290 to get the temperature to the desired 300.  When it gets to 300 it will turn the burner off.  Quite possibly the stone will keep on transmitting heat after the burner is off and the oven will heat up to 303 before it evens out.  A PID would know this and therefore perhaps only turn the burner on 'till 298.   It would also know that if the temperature is dropping that it doesn't need to wait until 290 to turn the burner on.  It might give a short blast of heat at 295.

btw, what does..."I think the above would just about fit on the back of a postage stamp! "  mean?

I know next to nothing about what I'm writing ;D


Offline Chicago Bob

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #130 on: August 28, 2012, 12:09:24 AM »
Dang..'ol PID pretty smart...
And I think you have much more to say than a postage stamps worth, thanks!
btw, why would PID not apply for your situation(humor me please)  ;)
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Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #131 on: August 28, 2012, 12:23:54 PM »
Now I'm really just winging it.

Generally I understand that a PID can vary the power depending on how far away you are from the desired temperature.  If you only open the oven door once or twice it could tell the burner to blast at 1/2 power for 2 minutes.   If you are constantly opening the door and the temperature is dropping rapidly the PID would recognise what is happening and tell the burner to run at full power until you are near to the desired temperature (set point SP).   This sounds great but the switching mechanisms for the burner on/off that I have come across only do on or off.  I think if I start delving into variable gas flow mechanism I would really give myself a headache.

The other problem I see is that you have to dial in the parameters yourself and then it will learn from there.   So you tell it the SP (desired temperature) and temperature difference where it has to start working.   It will learn to keep the temp. at your desired 300 C within a degree or 2 but once you start putting different loads on the system it will be turning on and off just as many times as a normal thermostat.   Don't really see its advantage here.   If you were curing pepperoni in a closed fridge then it could maintain the humidity very constantly.  But once you start opening and closing doors erratically then it has no real benefit.

That was fairly long winded without saying an awful lot.  If anyone can confirm that I'm not talking bo##ock$, please do! 

Also if you're reading Scott, what do you think about the aluminium plate and warping?

Offline Chicago Bob

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #132 on: August 28, 2012, 01:00:21 PM »
Gotcha Squid, thanks. I guess it just sounds like an additional unnecessary expense (and something else that can burn out :))
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Offline shuboyje

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #133 on: August 28, 2012, 08:54:51 PM »
A PID and the thermostat do the exact same thing.  They turn something on and off to control temperature.  The only difference is how they decided when to turn it on and off.  A thermostat generally has some sort of set point as to when it turns on and when it turns off.  For instance it may turn on when the temperature is 5 degrees below the set point and turn off when it is 5 degrees above.  Nothing fancy.  A PID uses computer algorithm's to determine when to turn on and off to maintain much more accuracy.  Where a thermostat is static, a PID essentially learns based on the effect of it's past functions.  The longer it is used in a system, the better it will get.  Huge changes in load, like one day deciding your deck oven doesn't need a door might give it fits until it has time to readjust, but small changes would be no problem.  The mass in the oven acts to stabilize the temperature and would only help the PID to function even better.

The big reason I mentioned a PID in the first place was cost.  Task specific oven thermostats are pretty expensive here in the states, but a PID is $30. 
-Jeff

Offline Chicago Bob

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #134 on: August 28, 2012, 08:58:35 PM »
Thank you Jeff   ;)
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Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #135 on: August 29, 2012, 04:06:22 AM »
Thanks for clarifying that Jeff

Here is the burner I had made in Bangkok

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #136 on: August 29, 2012, 04:07:29 AM »
Close up of the 2mm ports

scott123

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #137 on: August 29, 2012, 05:43:03 AM »
Richard, I wouldn't put any thickness of aluminum that close to the burner. Is steel plate really that much more expensive than aluminum?

That's a pretty nice burner, btw. I think the holes need to be closer together- like double the number you have now.  That might help it light a bit better.

Offline Sqid

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #138 on: August 29, 2012, 07:45:14 AM »
Hi Scott.  How ya doin?

That's a bummer!  I thought I was going 'cutting edge' oven design with an aluminium plate. :'(  Trying to avoid getting hot spots in the oven.
Steel is cheaper 6mm.  About $7 sq ft
Stainless 6mm.  About $19 sq ft
Different thicknesses are available.

Is there any major advantage to using SS rather than normal steel and would 1/8" be suitable for both?
Maybe steel, then aluminium, then firebrick hearth?

The burner ports are 8mm apart.  If I double the number of holes they will be very close - 3mm.  Does that sound about right?

buceriasdon

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Re: Want to build a gas fired deck oven. Any plans available and suggestions?
« Reply #139 on: August 29, 2012, 08:18:20 AM »
Richard, I assume the burner was copied from a similar burner, correct? Also you will be using natural gas? How long before you can trial fire the burner? Curious to see how far natural gas can push a flame.
Don


 

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