flue

[hungng]

I really like the way this contributor (attached photo) has done their flue with the curved metal base part going across the top of the entry.
I have access to all the equipment needed to make one similar but thought I'd just ask what everyone else thinks of this style. Would it work as efficiently as the more raised style that you see a lot of builders doing? Would it heating up and expanding cause bricks to crack and should i allow room for a bit of expansion?
Thanks to whoever contributed this photo by the way. Its a really nice looking build.

[azatty]

Re: flue

The reason for the "raised style" that you see is the extra height allows the creation of a "funnel" or "throat" that ends at the actual flue. It drafts across the entire arch opening instead of a single point halfway across the arch. Efficiency-wise, the only real indicator is whether it keeps smoke from coming out of the front of the oven in regular conditions. If it does that job, then it's plenty efficient.

Whether the masonry around it cracks or doesn't crack depends on how it's installed. Most likely, the steel plate is simply floating in a channel cut into the brick (or formed into the concrete), and maybe is secured with a couple pins drilled into the brick (at least that's how I'd do it). If I were worried about smoke escaping out the gap between the masonry and steel, I'd lay some fiberglass rope/gasket in the channel.

[Les]

Re: flue

I would contact the builder directly to see if there were issues. My opinion is that is should draw fairly well after it gets to temp. For all the exhaust to find the pipe in the beginning is pretty optimistic. In regard to the temp differential, I think you would be fine. They build bridges with steel inside of concrete so the materials co-exist fairly well together.

[david s]

Re: flue

I would contact the builder directly to see if there were issues. My opinion is that is should draw fairly well after it gets to temp. For all the exhaust to find the pipe in the beginning is pretty optimistic. In regard to the temp differential, I think you would be fine. They build bridges with steel inside of concrete so the materials co-exist fairly well together.

That's true, but in an oven situation the denser and more heat conductive material (steel) heats up way faster than the refractory that surrounds it. This creates greater expansion of the steel and can crack the refractory, which is exactly what happened to my second two ovens that had 1.2mm thick stainless steel flue pipes surrounded by castable refractory.
I think you need to make provision for the fact that the steel will expand.

[brickie in oz]

Re: flue

The flue looks way too small to me, the smoke will find the path of least resistance, ie the entry.

[hungng]

Re: flue

My oven is 850mm interior. I was thinking of a 150mm flue. Does that sound big enough?

[brickie in oz]

Re: flue

Bigger is always best.
150mm is on the small side.

[david s]

Re: flue

In ancient, outmoded, imperial measurement system, that's a 6" flue for a 34" oven. Pretty much standard, relative to other members ovens.