Pomeii 42" Germany

[Tinnefeld]

Hello everybody I' Niklas and live in Germany, I havé started to build and have now a couple of questions.

Is it nessesary to have a waterproof layer under the Calsi board? The black stuff is water resitant but is it nessesary to use... how much heat it will stand is also a good question.

Is a thermal break a good Thing to do? Will the hole dome be seperated with an insulating layer from the chimney?

greetings

[Gulf]

Tinnefeld,

Welcome to the forum. No, the moisture barrier is not absolutely necessary. But, it does guard against water wicking up from the concrete hearth to the insulation layer.. Your consern about it getting too hot is a valid consern. If that happens, it is because there is insufficent insulation between it and the oven floor brick. Most builds that I have seen lately are using multiple layers of insulation. Some use a layer of v/pecrete and then the insulated board or doubling up on the insulation board. I don't see where there could be a problem with just one layer of board, unless the insulation board had open gaps at the seems.

The jury is still out on the thermal break. At least, until someone builds and compares two almost identical ovens (one with and one with out a thermal break). I don't know if that will ever happen . With or without, the oven will perform just fine.

[UtahBeehiver]

Drilling a weep hole under the "black" plastic has also been recommended to ensure any moisture has a way to migrate out. It could make a difference whether you enclose the over in a structure, or if the oven is under a protective structure vs on open igloo style, which can be more exposed to mother nature.

BTW, nice start and brick work.

[Tinnefeld]

Thanks a lot for answering so fast I try my best to cut the bricks as good as possible

I think I will take a way the black plastic, the isulating board is 50 mm thick and is not stacked there could be open gaps at least were small ones.

Is that a problem for keeping the heat. in the oven? Its possible to push them very tight. What do you think?

[Tinnefeld]

Hello again, here is my progress :-) . I think I have to do 4 more chains to close the oven.

My question is how big should the vent opening and the chimney diameter be. My oven is 40 inch in diameter.

I hope you understands what I mean.

Greetings

[UtahBeehiver]

Ovens 40-42" inside diameter should have a 8" chimney. Based on a 8" ID round chimney, the area is 50.3 square inches. So your vent opening at least 50.3 inches. Square or rectangular chimneys are not as effective flow wise as round chimneys. That said, the vent opening needs to have a smooth transition to the chimney. Look at JRPizza's vent transition if you want to see smooth.

[Tinnefeld]

I,ll do that. Thanks for a fast answer :-)

[Tinnefeld]

Today our chimney sweeper came to take a look. He was wondering why the Diameter had to be that big. The Chimney also have to be sweeped once a year. Would a diameter of 20 cm at the vent and then a change to 15 cm for the flue? The Flue stands next to the oven and need to be 3 metres high. Make it any sence?

[Tinnefeld]

[david s]

The Pompeii oven is not a simple updraft system that your chimney sweeper would be familiar with. It is a cross draft system which requires greater draw from the flue to make it operate correctly without having smoke escaping out the front.. The extra height of the flue will give it extra draw although I'm not sure it would be enough. The bend you have proposed should not be horizontal it is much improved if it is 45 degrees. Also the vertical section of the flue should be closed below the oven so the draw will be from the oven rather than from whatever is below it.

[Tinnefeld]

Hello again! I have started to cure my oven . How small or big should the fire be? This was my first one.
Greetings

[david s]

Start reading here.
#1

[Tinnefeld]

Thank you! Still one question.. where should the temperature 100 F be? Top of the dome or just above the fire?

[david s]

If you measure the temperature at the top of the dome from the inside it is going to be way hotter than the base of the dome. This big difference in temperature readings also means a big difference in thermal expansion which creates huge stresses on the refractory. Allowing the oven to cool again allows temperature to equalise and you can go again. Try taking the temperature about halfway down the dome as an average.As the oven begins to dry it will start to burn the fire much more efficiently and this is when you need to be careful not to let the fire gallop away because the base will be still much lower in temperature.

[Tinnefeld]

I'll do that! Thanks