Want to build a gas fired deck oven. Any plans available and suggestions?

[Sqid]

I'm pretty much decided that I shall go with the 9" square bricks, that are available to me, for the hearth.   This will give me an internal deck dimension of 54"x27".

Can any one explain how the heat dampers work to regulate the top and bottom temps?

[scott123]

Can any one explain how the heat dampers work to regulate the top and bottom temps?

The dampers are just extensions of the deflectors under the stones.  The bottom and side deflection is taking the rising heat, and, rather than sending it right into the stone (bottom heat), it's redirecting the heat up the sides of the oven and into the top of the baking chamber, heating the ceiling and the top of the pizza (top heat).

2" thick bricks will take a while to pre-heat- most likely at least 2 hours. They will also stay hot long after you're closed.  They should give you stellar recovery between pies, though. A thicker brick should be naturally more diffusive, so you might not need that much deflection underneath- especially since, as you add more mass (in the form of deflection), the greater the extension on the pre-heat. The hearth heat, with all this mass, is going to be pretty unresponsive. If, for some reason, you need to turn the thermostat up, it will take at least a couple of hours for the heat coming from below to reach the top of the hearth. Not that thermal mass is bad- it's just slow to respond and will take some time to get used to.

A steel plate ceiling might be the answer, but I think, due to the lack of conductivity of brick, the bricks will respond a bit better to a frequently opened door. Still, if you have better access to steel... I might give it a shot. 1/2" sounds like a good amount of thermal mass.

[Sqid]

The dampers are just extensions of the deflectors under the stones.  The bottom and side deflection is taking the rising heat, and, rather than sending it right into the stone (bottom heat), it's redirecting the heat up the sides of the oven and into the top of the baking chamber, heating the ceiling and the top of the pizza (top heat).

2" thick bricks will take a while to pre-heat- most likely at least 2 hours. They will also stay hot long after you're closed.  They should give you stellar recovery between pies, though. A thicker brick should be naturally more diffusive, so you might not need that much deflection underneath- especially since, as you add more mass (in the form of deflection), the greater the extension on the pre-heat. The hearth heat, with all this mass, is going to be pretty unresponsive. If, for some reason, you need to turn the thermostat up, it will take at least a couple of hours for the heat coming from below to reach the top of the hearth. Not that thermal mass is bad- it's just slow to respond and will take some time to get used to.

A steel plate ceiling might be the answer, but I think, due to the lack of conductivity of brick, the bricks will respond a bit better to a frequently opened door. Still, if you have better access to steel... I might give it a shot. 1/2" sounds like a good amount of thermal mass.

Hi Scott

Thanks for the quick reply.  I'm under the impression that the dampers are like movable flaps that limit the movement of air from the bottom chamber up the sides to the top chamber.   
The deflector that I am planning on using will be a 54"x27" mild steel 3mm sheet.
The dampers that I want would enable adjustment of the top and bottom heat as in this Garland:
www.garland-group.com/docs/.../g_go_br_pyrodeck_gpd48gpd60.p.
Not sure if this is standard or not in most pizza ovens.

I know 2" is on the heavy side. I would much prefer 1.5" but nothing suitable available. 

As to the ceiling.  On the umpteenth rerun of the Marsal vid you sent me I noticed that they are using insulating bricks on the ceiling which would be in line with what you say aboout low conductivity.  I had thought earlier that I would need a good radiating heat source on the ceiling to keep up with the hearth.

[scott123]

I don't think the Marsal has an adjustable damper.  It's an interesting concept, but I'm not sure what it brings to the table. With the  fact that, in a bottom heat source scenario, the top is rarely as hot as you want it to be, I'm not sure damper adjustment is really all that necessary. I would think that you would want the air flow to always be max coming up from below.

The ceiling bricks on the Marsal aren't insulating.  They're plain vanilla firebrick- like the brick's you're using as a hearth. The decks are fibrament- cast reinforced refractory cement and the ceiling is traditional firebrick.  They also offer a firebrick hearth option.

[Sqid]

The ceiling bricks on the Marsal aren't insulating.  They're plain vanilla firebrick- like the brick's you're using as a hearth. The decks are fibrament- cast reinforced refractory cement and the ceiling is traditional firebrick.  They also offer a firebrick hearth option.

I don't know what vanilla refers to.  Is it just the colour?
However I don't think they are they are the same as the bricks I'll be using for the hearth.   In the video they mention that they are "lightweight firebricks".   I have seen similar bricks available here but they are very different from the 2.3g per cu cm that I will be using on the hearth.

I have presumed they are insulating.  They use the same bricks at the back of the Marsal where it would be disadvantageous to have radiant heat.

[Sqid]

I don't think the Marsal has an adjustable damper.  It's an interesting concept, but I'm not sure what it brings to the table. With the  fact that, in a bottom heat source scenario, the top is rarely as hot as you want it to be, I'm not sure damper adjustment is really all that necessary. I would think that you would want the air flow to always be max coming up from below.

It doesn't appear to have a damper.   The Garland  that I posted a crappy link to does.   Here's one that should work:
http://www.google.com/url?sa=t&rct=j&q=garland+pizza+oven+damper&source=web&cd=1&cad=rja&ved=0CCsQFjAA&url=http%3A%2F%2Fwww.garland-group.com%2Fdocs%2Fuploaded%2Fgar%2Fproducts%2Fg_go_br_pyrodeck_gpd48gpd60.pdf&ei=7sxIUMb1A5HJrAeDhYHgDQ&usg=AFQjCNEIeGpn76uEZDj9KwJwBA1Zt9-xXg

I'm still thinking to have a top burner but was considering a hybrid using maybe smaller vents at the side.

[scott123]

I don't know what vanilla refers to.  Is it just the colour?
However I don't think they are they are the same as the bricks I'll be using for the hearth.   In the video they mention that they are "lightweight firebricks".   I have seen similar bricks available here but they are very different from the 2.3g per cu cm that I will be using on the hearth.

I have presumed they are insulating.  They use the same bricks at the back of the Marsal where it would be disadvantageous to have radiant heat.

Richard, 'vanilla' is a another word for 'standard,' ie, nothing special.  The narrator uses the term 'lightweight' in the context that the bricks are lighter than the 70 lb. fibrament slabs.  I promise you, they aren't insulating bricks.  Insulating bricks have very little mass. Without the mass, they don't radiate.  The radiant heat from above is the entire purpose for the brick ceiling. The bricks absorb heat into their mass and then radiate it down onto the pizza.  In non brick ceiling ovens, when you turn up the oven very high, the bottoms start burning before the tops are done.  The additional top heat from the brick ceiling helps to balance this out.  Without the brick ceiling, you're talking about 7 minute bakes, at a minimum. With the radiating mass of the bricks, you can get down to that magic 4 minute bake. 

[scott123]

I'm still thinking to have a top burner but was considering a hybrid using maybe smaller vents at the side.

I hate to sound like a broken record, but I've never seen a top burner in a gas deck oven. The thermodynamics is pretty simple.  Good deflection underneath, proper sized side channels, a brick ceiling to absorb and radiate heat, along with an abundance of BTUs. 

Top burners, on the other hand, seem far more complex. You've got to make sure the top burner has it's own air supply. It seems like, from home ovens, that gas broilers tend to work better pointed upward with a shiny metal sheet to reflect the heat back down. You're also talking about another pilot light/ignition.

[shuboyje]

I gotta agree with Scott here, although originally I thought a top burner would be easier to engineer then the deflectors and baffles of a bottom only oven, now that I've seen them there really is nothing to it.  As an added benefit I feel it would be easy to add a top burner after the fact if the bottom burner only configuration isn't working for some reason, so you always have that as a plan b to fall back on.

[Sqid]

Richard, 'vanilla' is a another word for 'standard,' ie, nothing special.  The narrator uses the term 'lightweight' in the context that the bricks are lighter than the 70 lb. fibrament slabs.  I promise you, they aren't insulating bricks.  Insulating bricks have very little mass. Without the mass, they don't radiate.  The radiant heat from above is the entire purpose for the brick ceiling. The bricks absorb heat into their mass and then radiate it down onto the pizza.  In non brick ceiling ovens, when you turn up the oven very high, the bottoms start burning before the tops are done.  The additional top heat from the brick ceiling helps to balance this out.  Without the brick ceiling, you're talking about 7 minute bakes, at a minimum. With the radiating mass of the bricks, you can get down to that magic 4 minute bake.  

Don't want a 7 min bake!!!!!!!  So I guess it's down to a lack of my language abilities .   They call the bricks either, "heat holding" or "heat capable".  The 9x9" are heat holding and 2.3g/cu cm.  I will find out about the other type, I think vanilla.  "Lightweight" may have been used to describe the overall weight but I doubt they would have chosen that word if the SG was heavier. 
According to this thread fhttp://www.pizzamaking.com/forum/index.php/topic,5645.0.html
fibroment has a mass of about 1.8g/cu cm which is lighter than my 9x9s but probably heavier than the vanillas available.

If you have heat coming up the sides it will also be radiating so I can accept that the bricks at the back are also radiating.

Leaning towards 1/2" steel for the ceiling as I only have small bricks which would be a pain to hold up evenly.

[Sqid]

I hate to sound like a broken record, but I've never seen a top burner in a gas deck oven. The thermodynamics is pretty simple.  Good deflection underneath, proper sized side channels, a brick ceiling to absorb and radiate heat, along with an abundance of BTUs. 

Top burners, on the other hand, seem far more complex. You've got to make sure the top burner has it's own air supply. It seems like, from home ovens, that gas broilers tend to work better pointed upward with a shiny metal sheet to reflect the heat back down. You're also talking about another pilot light/ignition.

If I could go look at some pizza ovens I probably would just copy the popular mainstream design.  There isn't a single one in this country as far as I know.   We do have a lot of ovens which use a top and a bottom burner.  Extra expense and all that!

I freak out regularly when someone mentions difficulty with top heat.  Turn the burner on high to get the top heat back, as if that wont i increase the temperature of the already hot hearth.   Dampers I can see, to some extent, may give you control over top/bottom heat.  Seems most ovens utilise them but can't find any reference to them for the Marsal.   I'm paranoid that I will not be able to get a consistently high top heat after I've gone to all this trouble.   The Woodstone range do utilise top and bottom burners, don't know if anyone has any experience with these.

The air supply will come from the forced blower attached with the control system.

[Sqid]

I gotta agree with Scott here, although originally I thought a top burner would be easier to engineer then the deflectors and baffles of a bottom only oven, now that I've seen them there really is nothing to it.  As an added benefit I feel it would be easy to add a top burner after the fact if the bottom burner only configuration isn't working for some reason, so you always have that as a plan b to fall back on.

Adding a top burner later (plan B) has been the way I've been thinking.   More recently, without full knowledge of the damper system and with no one here in Burma who has any experience with this, I'm thinking it will be easier for me to go with a 2 burner system from start.   Incorporating the side vents as a courtesy to traditional pizza deck design or not.

Thanks for your thoughts.

[scott123]

Richard, I can't speak for the bricks you have there, but in most of the world, there's two types of firebricks.

Insulating - extremely light, Styrofoam light

Regular - heavy

Regular firebricks can have a range of densities, but the differences are not that great.  Compared to insulating bricks, they're all heavy.  The bricks you're using are regular firebricks, as are the bricks in the ceiling of the Marsal.

The Garland oven might do things a bit differently, but the Marsal is the same approach as the Baker's Pride y-600.  Between the two, that's more than 50% of the market.  You don't really need to see any more ovens, because they all pretty much mirror the Marsal. Once you've seen inside the Marsal, you've pretty much seen inside of them all.

I'm 99% certain that the adjustable dampers on the Garland are for lowering top heat for longer non NY bakes.

[Sqid]

Scott - You are absolutely right about the bricks.  They are the same weights.   Only difference is, the local ones are a little brittle and crumbly.

The heat controlling dampers are also used on the Y600
http://www.tumblr.com/tagged/bakers-pride-deck-oven

I've heard that there is a 'main man' dealing with fire bricks,  So I'm going on an excursion today to find Mr Big and see if I can get a more suitable size.  I was thinking of making a 3 pipe burner to run along the center of 3 rows of bricks which would give me 27" depth for the oven chamber.   Would like to get a few more inches of depth.   Mt present oven  has 33" which is adequate.

[scott123]

The y-600 has adjustable dampers? I stand corrected.  After reading this, I just did some digging on the Marsal.  Apparently that has dampers as well, so I've been wrong about that also. Regardless of my incorrect information, I still strongly believe that, with the bake times you're working with, you're never going to want to dampen/limit any heat reaching the top of the oven, so, in your case, I still don't think dampers are necessary.

Your firebricks are a little 'brittle and crumbly?'  I'm sorry to hear that.  I think that rules them out.  If a piece breaks of and ends up on the pizza, someone could easily chip a tooth. Are you sure they aren't just a bit sandy?  Sandiness can generally be washed off.

Don't be too concerned with larger firebrick dimensions, by the way.  As firebricks get bigger they can be less sturdy and less flat and the lateral heat transfer on large whole bricks is really not that much better than smaller bricks, as long as the smaller bricks are butt up against each other.

This is a bit outside of my current skill set, but perhaps, with your troubles tracking down firebrick, you might be able to cast your own fibrament-ish hearth.  I know they reinforce it with something- most likely fiberglass. If I were doing it, I might opt for stainless pins. With the right cement mix and perhaps something along the lines of a homemade vibration table...   

[Sqid]

The local firebricks are a no go for the hearth.  I may be able to use them for the back and the ceiling.  I'm heartened that you think lateral heat transfer won't be such a problem so I shall probably go with the 9x9s that were made in Japan.   Think they will be better than cobbling together a homemade fibrament  hearth.

Another reason I wanted larger bricks was to get a little more depth to the oven.  3 parallel burners would put a flame underneath the center of the 3 rows of bricks.  27" will just about suffice but it might be a bit tight getting the back row of 12" pizzas.  Don't need 36" depth which would use 4 rows of bricks.   Could use 4 rows (and 4 burners) and have the back wall of bricks sitting on top of the last row, that would give me 34" but I think that row wouldn't be the same temperature as the other rows.

[Sqid]

Still concerned about the lack of control of top and bottom heat.

Every time I talk to you guys I think that bottom heater, side vents is the way to go.   When I talk to my oven guys here I feel that I should be making 2 heating chambers!!!

If I go the way that's been suggested, bottom heater with option to add top at later date.  There are a couple of points to decide now.

1)  Height of chamber.  Allowing that I may decrease the height by 1.5" if I add a burner later.

2)  Position of the thermocouples.   In my bread oven: one of them is about 3/4 of the way up the chamber.   The other is under the steel deck.
I don't mind installing 2 thermocouples to begin with.  For the hearth, I was thinking that half way into the 2' brick would be the best position.  Any ideas?

[Sqid]

Pics of the firebricks.
The paler one is local and it's very easy to scrape it away.

[scott123]

Yes, that local firebrick is not what you want.  You might be able to use if for the back wall, but I wouldn't use something that sketchy on the ceiling for fear that it would drop a piece on the pizza. The Japanese firebricks look like winners.

You want the smallest possible oven height that you can comfortably work with, i.e., access the back pies with a peel.  The lower the better, as the ceiling height plays a role in top heat.  If you can get away with 6", that's what I go with, but if you want to play it a bit safer, go with 7" (from the hearth to the bottom of the ceiling).

Bear in mind, if you go with bricks for the ceiling, you most likely won't need the bricks if you decide to add a top burner, so you may not have to accommodate the height of the burner in the original plans.  Perhaps you could attach your ceiling in such a way that it could be adjusted up or down, to accommodate an eventual burner should you decide to go that route- as well as height tweaks to get it as low as possible.

I'm not 100% certain about where to the thermocouples.  Are you thinking of drilling a hole in the firebrick?  I'm thinking, for the top, you'd want it as far away from the side vents as possible- maybe the middle top.

[Sqid]

I watched a video about Peerless ovens (admittedly, they are only using 60,000 Btus) and the operator was singing their praises.  He also mentioned that the pizzas cook faster at the back as if that were a good thing.   Marsal talk about evenly cooked pizzas every time however if the pie is placed close to the back it will surely cook faster on one side.

I have been considering not having a back wall of refractory bricks.  This would even out the heat for any position in the oven.   It also poses the question about the side walls behind the vents - do you know if the walls are made of refractory bricks or insulating material?

What is the smallest height with which I would be comfortable.  Hmmm     I'm used to the cavernous 12 - 14" that I'm working with atm.   8" seems to be the industry standard with some ovens using a slightly lower 7" door size.   Many manufacturers give an option for 10" height maybe to accommodate bread or lower skilled people like myself!  I get the idea of the lower, the better... but!  Will talk to my steel guy today and find out about adjustable ceiling.  Trepiditiously (is that a word) I'll say I'm leaning towards 7" door 9" ceiling (to later accommodate a burner if needs be).

With or without top burner I feel that the oven will perform better with a heat retaining ceiling.  My guy suggested 1/2" mild steel.  Very simple and probably radiates heat better than brick but I doubt it has the thermal mass of firebrick.  Any thoughts?

I think drilling a hole for the thermocouple is the way to go but don't know about the logistics.   With a 2" hearth, there will be a long time lag between heat being applied at the bottom and it traveling to the top, where its needed.   Probably an ideal situation for a PID but I don't want to  go that route.

Thanks for your help.