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mrchipster 10-19-2012 09:21 PM

Need Help with troubled oven
 
4 Attachment(s)
Spent some time today with another oven owner here in Minnesota discussing their oven and how to increase it's performance over just making pizza.

They purchased a 36 inch cast oven made in Minnesota, Artesian ovens.

The reason we initially met was because of a contact we made because they were trying to sell some foamglas on Craigslist. The oven came with enough 4 inch thick foamglas board to be placed under the entire oven, but some of the local "Experts" on oven building supposedly engineers talked them out of installing the provided insulation and to put down 1 inch of ceramic board under their oven because

-- get this...

"How would the heat of the oven be able to get into the supporting slab with all that insulation in between. You would not have enough thermal mass to cook"

Well their 36 inch oven takes over 3 hours to come up to pizza temps and I have my doubts about that statement because some of the photos I saw of them cooking pizza the oven is still not clear. So up to pizza temps is well... questionable.

They are also complaining about excessive smoking but I believe the oven may be wet due to no roof yet. And there is a high probability that they are burning damp wood.

I encouraged them to get the roof on, which is their own immediate goal; and to add insulation over the oven. They have even been told by the local "Expert" to cover the insulation with plastic... I have no idea where that idea came from. I told them not to add plastic under any circumstances.

I have added an image of the casting, there is no reveal at the entrance to where the inner arch would be, and I was told the manufacturer indicated that they should use a damper in the flue to control the heat loss via the flue.

The oven door provided is of course on the outside of the flue hole.

I suggested that they build a thick insulated door so that it would plug the arch opening and at the same time cover the flue hole as there is zero distance between the flue hole and the start of the inside of the dome at the transition.

At this time they do not have a roof or a way to block the flue so they are down to ambient in the morning after a several hour pizza party.

The Casting is already in place and has a partial house built out of 4 inch CMU and this is all mortared to and over the casting at the opening so no way short of major demolition to raise the oven and put more insulation under it.

One other thing that is very interesting about this oven, They have a gas bar at the back of the oven so they can heat it with gas but from what I gather they prefer to and primarily use wood.

I did not see the oven in operation and did not get any photos because it was raining out and I could not spend much time outside viewing it. But I did get a couple of older photos they have. and they are attached. The far away shot is the only one that barely shows the insulation. At least it is under everything.

The second photo is how it looked today.

Any and all comments welcome. I would like to help them get this oven at least partially usable for baking.

Chip

david s 10-19-2012 09:42 PM

Re: Need Help with troubled oven
 
It sounds like the oven is still wet as it's not getting to temp and is smokey. The second two ovens I built use the vent in this position and it does not work as well as having it right at the front and independent from the actual oven. Your idea re the door is a good one. If they have a gas burner I hope they have a flame failure device fitted.covering the insulation with plastic can help when curing because it will indicate the presence of moisture with condensation on the underside, but is not a good idea to have in place permanently. As you say, too late now to add the required underfloor insulation.

brickie in oz 10-19-2012 11:01 PM

Re: Need Help with troubled oven
 
It always saddens me to hear stories like this after some "expert" has intervened.

I installed a prebuilt oven last year for an Italian family, they tried to guide me on the proper oven building procedure, I obviously ignored them.

It took ages to convince them I was right, but the firing and heat retention was all the proof I needed. :)

WJW 01-25-2013 12:37 AM

Re: Need Help with troubled oven
 
It really is amazing how ignorant "experts" can screw things up. Let's be honest...this isn't rocket science. Ancient civilizations made highly efficient masonry ovens two thousand years ago. It's preety damn discouraging that, in the internet age, a guy would put the flue behind the door of a masonry oven.


All that being said, it seems to me like this oven is fixable.

Why couldn't the guy stack and mortar courses of block against the front face of the stand so as to move the front of the stand out eight inches. So now the stand is now eight inches further out...why couldn't he simply use firebrick to plug up/brick over the existing flue, install a reveal at that location, and then construct a new flue/chimney outside the door over the newly enlarged stand.

Granted it's a project, but it would convert a disater into a totally functional pompeii style oven IMO.

Bill

brickie in oz 01-25-2013 12:53 AM

Re: Need Help with troubled oven
 
Quote:

Originally Posted by WJW (Post 144528)
It's preety damn discouraging that, in the internet age, a guy would put the flue behind the door of a masonry oven.


Yep, here we are in the year 2013 and in the internet age, and yet the flue in my wood fired oven is indeed behind my door, and yet my oven works beautifully.
Hard to believe huh?

WJW 01-25-2013 01:09 AM

Re: Need Help with troubled oven
 
It's a different deal with you Al. You actually know what you're doing. Lot's of "experts" don't.

When you placed your flue behind the door you did so understanding the implications of that and installed a sliding damper that essentially removed the flue when it made sense to do so.

The whole problem with a flue behind the door is that you lose all the heat...unless you don't. Yours doesn't.

Apples and oranges.

Bill

cobblerdave 01-25-2013 04:27 AM

Re: Need Help with troubled oven
 
Gudday
I have a mate with a tunnel oven with an internal chimney witch is only used to flash up the oven. It caped of with a house tile and he cooks great pizza and bloody great slow cooks. I don't understand his oven his oven as much as my own but I always enjoy his cooking so I suppose its what you used too sometimes
By the way the way the tile over the chimney was my idea to start with but he has adapted to his own and he makes it work even thought the oven height to entrance ratio is well much below that "magic" 63 per cent.

Regards dave

Ps. His oven was with the house he brought and not his own build . It's a "store brought " oven of a common kit design

C5dad 01-26-2013 07:33 PM

Re: Need Help with troubled oven
 
Dave:

Need more info: a picture would be great as tile means different things to different folk! Is it an Alan Scott or deviation thereof?

I know that the community will assist. just a challenge to understand the basics of overall design.

CW

Les 01-26-2013 07:54 PM

Re: Need Help with troubled oven
 
Quote:

Originally Posted by cobblerdave (Post 144532)
Gudday
I have a mate with a tunnel oven with an internal chimney witch is only used to flash up the oven. It caped of with a house tile and he cooks great pizza and bloody great slow cooks. I don't understand his oven his oven as much as my own but I always enjoy his cooking so I suppose its what you used too sometimes
By the way the way the tile over the chimney was my idea to start with but he has adapted to his own and he makes it work even thought the oven height to entrance ratio is well much below that "magic" 63 per cent.

Regards dave

Ps. His oven was with the house he brought and not his own build . It's a "store brought " oven of a common kit design

Have a few Fosters there buddy? ;) I think the entrance "magic number" is what James dug out of the Pompeii ovens that he seen (it's been so many years and beer's that I don't recall). I'm sure it could be varied a lot and you would still have a functioning oven.

Tscarborough 01-26-2013 09:34 PM

Re: Need Help with troubled oven
 
Ancient ovens were not insulated well, they understood mass and airspace but not really the concept of thermal mass well insulated. It worked for them as they pretty much kept the ovens going all the time, so the mass was put to use.

Us hobbyists do not run the oven 7 days a week, so it is exponentially more important to have a discrete thermal mass well insulated.


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