Duratech chimney exterior feels hotter than it should...

[nissanneill]

Re: Duratech chimney exterior feels hotter than it should...

s
I feel that your 7" chimney will not cater for your 42" oven. I think that you will find that especially if you don't have a fairly large entry to the flue collecting and funneling the smoke up into the flue, that it will come out the front and blacken your front arch.
I would most certainly run the full length because as it heats up, it will draw better and literally suck the smoke that way.
I have an 8" flue that is 10' long (3 sections) and no smoke escapes through the front arch at all.

Cheers.

Neill

[sjmeff]

Re: Duratech chimney exterior feels hotter than it should...

So did you find a solution?

I found another thread that discussed leaving space between the stucco and the Duratech chimney and then filling the space with waterproof, high temp silicone sealant. That seems a lot easier than trying to add another chimney within my existing one.

BTW, laser thermometers don't actually use the laser to detect the temperature, the laser is just for centering the infrared detector.

Ah, good to know. Thanks!

[dpike]

Re: Duratech chimney exterior feels hotter than it should...

BTW, laser thermometers don't actually use the laser to detect the temperature, the laser is just for centering the infrared detector.

[mikes334]

Re: Duratech chimney exterior feels hotter than it should...

So did you find a solution? I know when I had a duratech issue I call the guys over at Chimney Liner Depot with my duratech chimney. They helped me out a lot.

[ThisOldGarageNJ]

Re: Duratech chimney exterior feels hotter than it should...

Hey Stephen,,
Im not sure if it would matter, going 7-8, But I would just keep it the same to avoid another strange variable....

Mark

[sjmeff]

Re: Duratech chimney exterior feels hotter than it should...

One other question regarding a lining inside my current 8" chimney. Does anyone have an opinion as to whether my proposed 7" lining should only go up, say, 12" rather than the full 36"?

The possible advantage to having it only go part-way up would be that the top part of the chimney would be a full 8" and might draw better.

The downside could be that the whole chimney still expands/contracts and causes the stucco to crack over time (even if it's not hot where the chimney and stucco meet).

I hope I'm explaining this well.

S

[sjmeff]

Re: Duratech chimney exterior feels hotter than it should...

Thanks, all, for your suggestions.

My current thinking is that I'll line the inside of the chimney with a single-walled, 7" stainless steel chimney liner that's wrapped in 1/2 inch of insulating blanket (I have some left over). The inner dimension of the chimney would be 7" rather than 8", so hopefully it would still be sufficiently large to draw for my 42" dome (and not make the front arch black from smoke).

The alternative is to insulate the outside of the chimney, but I think I'd have a tough time making it look right. I'm also not keen on the idea of stuccoing up the chimney.

If I were to do it all again, I'd probably build a brick chimney, but switching to that now would require too many modifications to what I've already built.

Fingers crossed.

S

[ThisOldGarageNJ]

Re: Duratech chimney exterior feels hotter than it should...

I agree with les, I built mine with Firebrick, But next time I would just use the sheet metal duct and perhaps build brick around it and insulate with vermicrete.... They make chimney liners like that now... even flexible ones... They fill the void with cement and vibrate the tube with a finishing sander to get the air out...

Mark

[Les]

Re: Duratech chimney exterior feels hotter than it should...

Stephen,

You can buy some inexpensive HVAC tubing at the box stores. Center it around your Duratech and dump in some vermiculite. I would think that will drop the temps enough to stucco.

Just my thoughts.

Les...

[sjmeff]

Re: Duratech chimney exterior feels hotter than it should...

Thanks, Mark. Having a number to work with is helpful (saves me a call to Quikrete).

I think the chimney is probably always below 300 degrees, but I'll check the next time I fire up the oven.

I see that Simpson makes a 3-walled chimney. It's pricey, but I may have considered that if I had known this would be an issue.

Cheers,
Stephen

[ThisOldGarageNJ]

Re: Duratech chimney exterior feels hotter than it should...

I used the acrylic stucco on the oven, There are spots on the transition that get about 250 degrees next to my fire brick chimney, When I called quickrete they told me not too be concerned till about 300 degrees, I hope they are right, But I have been cooking since may and so far so good

Mark

[Rastys]

Re: Duratech chimney exterior feels hotter than it should...

Sjmeff,
I just replied to a similar problem at:

https://www.fornobravo.com/forum/f9/6-8-chimney-pipe-7831.html

Check it out for some additional ideas.
You are always going to get your flue hot, way too hot for a paint, especially acrylics.
You cold always put an outer flue over the other one and pack it with some superwool insulation.

Rasyts

[david s]

Re: Duratech chimney exterior feels hotter than it should...

I was also concerned about the stucco to flue contact, so I put a layer of vermicrete around the flue, then the stucco over that.

[sjmeff]

Re: Duratech chimney exterior feels hotter than it should...

If your oven is fairly new then it is probably still eliminating water. This will make it hotter to touch. Keep firing and the problem may go away.

Thanks for the suggestion, David. In addition to the 8 curing fires, I've now fired it two times for cooking. I'll keep firing it several more times to see if it gets cooler.

I may be misunderstanding your intent, but you were not planning to put stucco on top of the steel duratech, were you? To my limited knowledge, thats not a good mix.

I'm not planning to stucco it all the way up the chimney, just around where it exits the roof as others have done (such as TheBadger: PhotoPlog - Enclosure).

I'm drawn to acrylic stucco as that seems to be the choice for the exterior render, but the heat might be an issue. I'm planning to call Quikrete on Monday to ask, but was hoping to hear from others who have used the same setup.

I also thought, perhaps, that it might be an issue with my chimney (maybe the insulation was omitted?).

S

[Les]

Re: Duratech chimney exterior feels hotter than it should...

My primary concern is that this is going to be too hot for the acrylic stucco finish I'm planning for the exterior, which would surround the chimney.

I may be misunderstanding your intent, but you were not planning to put stucco on top of the steel duratech, were you? To my limited knowledge, thats not a good mix.

Les...