Excited or Dissapointed - My Cool New Oven isn't Heating Up

[MarkJerling]

Hi Mark

Apologies for the late reply - it's been an eventful few weeks leaving me with little to no time for my oven.

I took your idea to my fabricator and he said it's doable - hopefully tomorrow he will collect the oven and follow your advice with a small adjustment . Instead of just a straight baffle like you sketched out, he will cover the chimney hole on the inside with a box type and then channel it to the oven mouth with the new a vent there - sorry my explanation is poor but in retrospect, the cold air will enter the oven, heat the fire and before exiting out the oven moth, it will travel up the new vent box as I would like to call it and then finally out the chimney hole. This will prevent the direct flames from travelling straight up the chimney, I've just attached a picture of the chimney as it is.

Wish me luck - hope that circumvents the issues I'm experiencing.

Again thanks for being awesome with the brilliant advice.

Take Care

I'm interested to know how the changes worked out?

[MarkJerling]

That sounds like a fine plan to me. Lets hope it works!

[Oven_Man]

Hi Mark

Apologies for the late reply - it's been an eventful few weeks leaving me with little to no time for my oven.

I took your idea to my fabricator and he said it's doable - hopefully tomorrow he will collect the oven and follow your advice with a small adjustment . Instead of just a straight baffle like you sketched out, he will cover the chimney hole on the inside with a box type and then channel it to the oven mouth with the new a vent there - sorry my explanation is poor but in retrospect, the cold air will enter the oven, heat the fire and before exiting out the oven moth, it will travel up the new vent box as I would like to call it and then finally out the chimney hole. This will prevent the direct flames from travelling straight up the chimney, I've just attached a picture of the chimney as it is.

Wish me luck - hope that circumvents the issues I'm experiencing.

Again thanks for being awesome with the brilliant advice.

Take Care

[MarkJerling]

Hi Mark

Definitely going to brick the entire floor of the oven - also gonna remove the underneath plate that's creating an air gap.

If you don't mind, please can you sketch the baffle you referring to.

You truly have been a great help - can't thank you enough.

Take Care

Here's a rough sketch of what I think can help. ( Cross sections)
Obviously, I hope I understand how your oven has been built. If my understanding is not correct, then please let me know.

[Oven_Man]

Hi Mark

Definitely going to brick the entire floor of the oven - also gonna remove the underneath plate that's creating an air gap.

If you don't mind, please can you sketch the baffle you referring to.

You truly have been a great help - can't thank you enough.

Take Care

[MarkJerling]

Hi Mark

Thanks for your response.

I think you are correct - the flue is sucking away most of the heat since the flames actually travel up the flue instead of lapping the dome to the opposite side of the fire. I'm trying to understand a little more about the baffle - are your referring to a damper on the flue itself so i can open and close it? I'm actually going to ask my fabricator if he can add that on for me. I was also think of closing the flue off temporarily and see if that makes any difference.

Sorry for the delay in reply. We've been away from home. I was not thinking of a openable baffle in the flue, but rather a baffle at the top of the oven so as to prevent all the hot air which should be held at the top of the oven from going directly up the chimney. Let me know if you need a sketch.

Regarding the firebrick, yes it is elevated ontop of another piece of sheetmetal - I did this to help with the airflow underneath the brick but perhaps the though behind it wasn't all that good. I can easily remove the sheetmetal and let it sit flat on the base?

I wonder also if another design flaw maybe a contribution factor to the heat issue i'm experiencing. I have firebrick on one side of the oven only i.e. the right side and then on the left side of the oven I created a Steel Tray to hold the logs and keep the ash contained - this steel tray sits directly on the base of the oven. I'm wondering if the installing firebrick over the entire floor and then left my fire burn directly on the firebrick - will that help in any way?

While I think your contained fire idea has merit, it means you can't spread the coals over the whole floor and you can't move your fire location from one part of the floor to another - all features of a typical wood oven. I would consider removing the ash grate and pave the whole floor with firebricks and go from there.

[JRPizza]

Burning directly on the firebrick would help, as would eliminating the airspace below as MarkJerling pointed out. I'd consider adding some type of CF board on the bottom and making the layer of brick extend over the entire surface.

[Oven_Man]

Hi Mark

Thanks for your response.

I think you are correct - the flue is sucking away most of the heat since the flames actually travel up the flue instead of lapping the dome to the opposite side of the fire. I'm trying to understand a little more about the baffle - are your referring to a damper on the flue itself so i can open and close it? I'm actually going to ask my fabricator if he can add that on for me. I was also think of closing the flue off temporarily and see if that makes any difference.

Regarding the firebrick, yes it is elevated ontop of another piece of sheetmetal - I did this to help with the airflow underneath the brick but perhaps the though behind it wasn't all that good. I can easily remove the sheetmetal and let it sit flat on the base?

I wonder also if another design flaw maybe a contribution factor to the heat issue i'm experiencing. I have firebrick on one side of the oven only i.e. the right side and then on the left side of the oven I created a Steel Tray to hold the logs and keep the ash contained - this steel tray sits directly on the base of the oven. I'm wondering if the installing firebrick over the entire floor and then left my fire burn directly on the firebrick - will that help in any way?

[MarkJerling]

Looking at your video and photo posted, I see a number of potential areas for improvement.

1. As your flue is going out from the top of the 'dome', you will see rapid heat loss. I'm guessing here, but I think you should see some improvement if you have a baffle so that you can retain some heat under the top of the dome. At the moment, all your heat will be sucked up the flue. You'd want that baffle to extend down behind the flue to a height somewhere between the door height and the top of the 'dome' height.
2. I see your base fire bricks are elevated above an air space. This is bound to provide convection air movement so your tiles will constantly be cooled due to air being sucked in below. I'm not surprised, therefore, that you're saying the underside of the oven is cool to the touch. As others have pointed out, you'll struggle to retain heat with such thin floor tiles.

As others have pointed out, this oven will function very differently to a brick oven - I believe we wrote about that in your design thread.
Good luck!

[Oven_Man]

I guess this oven is a learning curve - the more I use it, the better I hopefully get at making it work.

[UtahBeehiver]

JR is spot on. The 1" thick floor will need to be replenished with heat more often. 2" is a minimum thickness for thermal mass on floors (even with 2", depending on the number of pizzas needs replenishing of heat). So you just have to adjust and factor in raking the to coals over the floor more often. Not much you do about the thermal mass on the dome other than keeping a live fire.

[JRPizza]

I think your design is going to lend itself to more live fire cooking than retained heat cooking. It will heat up faster than a conventional brick oven and cool off faster too. Move the fire around enough to saturate your floor with enough heat to cook a crust and keep a fire going to one side to reflect heat back to cook the top of your pie.

[Oven_Man]

Thank you all for your responses.

JRPizza, you are 100% correct. There is very little to no thermal mass in-between the domes. The floor just has 1" firebrick for thermal mass - I don't know thicker firebrick would make any difference.

deejayoh, I brought the flue as close to the oven opening as possible but I hear your concern that the flue and vent should be in front of the opening so hot air circulates properly in the oven before finding it's way back out the vent and flue.

Petter - I followed the guidelines for the opening - I kept the height at 63% of the inner dome height. Not sure what guidelines there are for the width but I went with a width similar to a brick oven.


I see Forno Bravo has the Bella Medio stainless steel oven https://www.fornobravo.com/PDF/bella...dio-manual.pdf and looking at the dimensions, mine are almost the same. Anyone has the Forno Bella oven and can comment on the effectiveness of this oven?

Something interesting happened yesterday - after I was done with the oven, I left it to cool off but a short while later it started to rain so i quickly covered it with a water proof cover. After more than 2 hours, I went to check on the oven if it didn't burn through my cover (thankfully it didn't) and I noticed the inside was still quite warm (stone measurement was around 200f and baking steel was about 300f compared to the previous day when I let it cool - as soon as the coals died, the oven cooled off within 20 minutes. It seems the cover locked in the heat which boggles my mind since the insulation should be doing the same.

I'm just hoping that using this kind of oven is a learning curve compared to a similar brick oven

[Petter]

Additional reflections:


Look at the fire management of this guy:

https://www.pizzamaking.com/forum/in...pic=41907.1400

The oven is also a low mass stainless dual layer.


Your opening is very wide and has full height across meaning it draws a lot of cooling air at floor level.

[deejayoh]

Two issues I see with the design that may be contributing to your heat-up issues
1) can't be 100% sure, but it looks like your design has the flue inside the oven? That means the heat could be going up the chimney instead of circulating. (Similar issue to barrel designs)
2) you have insulating material between your dome layers, instead of something that will retain the heat. So there is very little mass to heat up, possibly exacerbating the issue above.