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Can these grills really survive high temps?

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So I just joined the cracked firebox club with the grill being 1 year old. It's not a bad crack, but I am one that needs to understand why especially since I was very careful. I always brought the grill up to temperature slowly on high heat cooks and brought it down slowly. I also never put the heat deflector low doing high heat cooks.  There were recently two cooks that I did. One was four racks of ribs and a pork should. The other was a pizza cook. Nothing extreme. Around 600 degrees.

 

I am unsure if the weight of all that meat is to blame or if the high temp pizza cook is the culprit. However, after discovering the crack I attempted to do another pizza cook. The grill reached 650 degrees indicating on the dome and as I opened the lid to place the pizza on I heard a loud pop. <INSERT FAVORITE SWEAR HERE>. I still haven't had time to look at what exactly failed, but from the loud pop I imagine the firebox is now in more pieces. I abandoned the cook and will investigate once the grill cools.

 

Which brings me to the question. Are these grills really able to reliably survive these high temps? I know they are capable of reaching those temps but does that means they are reliable around those temps? It seems that the fireboxes and gaskets do not have very long lifespans reaching temps that high.  Should I be getting this grill no hotter than 500 degrees to prolong its life?

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I cracked my firebox last October. I know mine was on pizza with deflectors in low position high heat. Live and learn. I got the replacement and winter came so I never changed it. Kept cooking in cracked box. It is now may and I still haven't replaced it. Last week I gutted my Joe's for a spring cleaning.

The box came out east and didn't fall apart all in one piece despite cracked. I decided why not and put it back in. Why change it???

Anyways you are covered and cooking with a cracked bix really doesn't matter. Plus warranty covers you

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So I just joined the cracked firebox club with the grill being 1 year old. It's not a bad crack, but I am one that needs to understand why especially since I was very careful. I always brought the grill up to temperature slowly on high heat cooks and brought it down slowly. I also never put the heat deflector low doing high heat cooks.  There were recently two cooks that I did. One was four racks of ribs and a pork should. The other was a pizza cook. Nothing extreme. Around 600 degrees.

 

I am unsure if the weight of all that meat is to blame or if the high temp pizza cook is the culprit. However, after discovering the crack I attempted to do another pizza cook. The grill reached 650 degrees indicating on the dome and as I opened the lid to place the pizza on I heard a loud pop. <INSERT FAVORITE SWEAR HERE>. I still haven't had time to look at what exactly failed, but from the loud pop I imagine the firebox is now in more pieces. I abandoned the cook and will investigate once the grill cools.

 

Which brings me to the question. Are these grills really able to reliably survive these high temps? I know they are capable of reaching those temps but does that means they are reliable around those temps? It seems that the fireboxes and gaskets do not have very long lifespans reaching temps that high.  Should I be getting this grill no hotter than 500 degrees to prolong its life?

Take you Joe out to 1000 if you need to. Your firebox is covered for lifetime replacements.

The FireBox is literally the punching bag and the defender of the faith of the ceramic Kamado world. It's takes all the hard hits so the rest of your Kamado stays in tact. The cracks from from expansion and contraction from heating and cooling. (Not Just Heating) You could be the most cautious Kamado user on the face of the earth and cracks can still happen.

A crack in the fire is just means the Firebox did it's job by taking the brunt of the high temps and by taking a blow so the rest of your Kamaodo remains pristine. A crack in the firebox is Kamado users badge of honor. It's just means you're heavy user.

As long as it's not two vertical cracks or 1 badly positioned horizontal crack than don't worry. With single vertical crack the prognosis is the patient (Mr. kJ Firebox) has anywhere from 3- 25 years to live.

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I don't have much to add, these guys are right.

One theory is that the first crack provides a good bit of natural thermal stress relief, the second crack May take longer to form.

I have taken my joe, with and without cranked fire ices to >750 F numerous times.

You did nothing wrong. Take a deep breath and cook.

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Cracks can (and do) happen with all brands of ceramic Kamados.  As Bosco stated earlier, having your diffuser in the low position enhances the probability of a crack forming.  Although the top half of your Kamado may only be 650, under the diffuser it becomes much hotter.  Remember a firebox cracking is partially determined by the firebox temperature, and not the dome temperature. Asymmetry of the actual fire has an impact, the ideal fire has the ceramic at a uniform temperature in the box, this tends to level out differences in expansion.  As an important note, an actual symmetrical fire is almost impossible to achieve.   Size matters, the sum of the heat distortion in the firebox, is bigger the larger the firebox is.  This is why we see cracked fireboxes more commonly occur the larger the firebox is.  This is part of the reason you will see me periodically post my Junior is the "searing station".  Most ceramics have a naturally occurring organic component, this unfortunately ensures non-uniformity in the ceramic (in stress and expansion characteristics).  When originally fired at the factory, the ceramic actually shrinks slightly, and stresses get created in areas which did not shrink uniformly.  Some pieces will crack at firing time; they are discarded.  Other pieces micro-fracture, and a visible crack will not develop until later.  The micro-fractured fireboxes may crack in shipping, or wait until they experience heat stress.  As some of you know, I like working on Kamados.  I have patched a few fireboxes (for my self, and covertly for others).  Once a box has cracked, the asymmetrical stress has been relieved.  This is the position I will then re-bond the cracked surfaces together.  If you try to bond the surfaces in a compressed condition, you are just re-introducing the stress back into the ceramic, and inviting a new crack.  When a crack forms, I re-bond the ceramic in the relaxed position (or if it is minor, ignore the crack), call the factory and invoke the warranty (if it exists) to have a spare sitting around.  A properly patched firebox has had its stress relieved, and will offer great service for years. 

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Would be interesting to know if the owners did the recommended low temp first few cooks & cool downs with their KJ's before bringing up to higher temps. I think three initial cooks no higher than 350 degrees is required. I have a large outdoor fireplace with a concrete exterior & ceramic fire box & the instructions required a few low temp initial fires & cool downs before any high temps which I did

& have had no probs for several years.

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I'm wondering why all kamados aren't designed with two piece fireboxes like the KK,mor at least a built in stress relief seam, i.e. a cut in the firebox on one side running from top to bottom. Any time you have a lot of unrelieved stress, and in conventional one piece fireboxes you have huge amounts of unrelieved stress, beyond a certain point, the heat induced stress overcomes the strength of the ceramic material. Something as simple as a 1/8" to a 3/16" slit will provide all the relief one needs. That would save KJ, Primo, BGE, etc. a ton of money is warranty associated claims. I don't get it. An ounce of prevention ...

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CC, I am usually the first to agree with your points, and I would have fully agreed with you a year ago.  Now that I have seen in person (or in pictures) a lot of firebox cracks some previously unknown factors have come to light.  The most common vertical crack is where the lower damper air enters the firebox.  The big however is: sometimes vertical cracks happen elsewhere.  Most companies which do put a relief slot in the ceramic, places it at the lower damper vent area (highest probability of cracking spot).  But if a vertical crack does occur somewhere else, the net result is a firebox which is literally split in two (and then splays outward making it unusable due to the classical firebox shape).  Without the relief slit, a single crack would not render the firebox unusable while the owner waits for a new box.  This makes relief slits a two-edged sword, it will prevent some failures, and exasperate other failures.  A true two-part (or more) firebox (designed to not splay out) is a great solution, as it reduces the amount of area for stress to build over.   

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You're right, Adder. The KK has a 2 piece firebox and I've never heard of or seen a broken firebox on a KK. Then again, the KK firebox is beastly and the airflow in a KK is significantly different as well. Airflow in a KK is forced up through the charcoal rather than flowing around.

I've seen many industrial ovens with stress relief built in to great effect. The one that didn't had real problems. I've always said a little bit of something is better than 100% of nothing. I'd wager that a slit in the firebox would result in much fewer warranty claims since the heat induced stress would be largely relieved. The probability of the a stress relieved firebox splitting is deminimus in relationship to one that isn't. Besides, how much cost is added to the manufacturing process versus a slew of warranty claims?

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Would be interesting to know if the owners did the recommended low temp first few cooks & cool downs with their KJ's before bringing up to higher temps. I think three initial cooks no higher than 350 degrees is required. I have a large outdoor fireplace with a concrete exterior & ceramic fire box & the instructions required a few low temp initial fires & cool downs before any high temps which I did

& have had no probs for several years.

 

I am not sure about others, but high temp pizza cooks are rare for me. And from what I have heard from others they tend to be at lower temps than others use.  So my firebox and ceramics went through multiple heat cycles most of them during low and slow cooks. And several cooks at 400 or below.

 

If anyone is curious. I have a firebox that has a stress relief cut in both the firebox and fire ring. It didn't save it.

 

I know the warranty is there, but in a year I have lost both a single piece heat deflector and now a firebox. The heat deflector broke during a time KJ had inventory issues and the port stike and it look a little over two months to get a new heat deflector. Luckily I had a spare or I would have not had a choice other than to not cook or get a replacement elsewhere.

 

The most concerning thing is the most recently high temp cook where once I opened the grill lid I heard the loud pop of ceramic breaking. It's obvious that the temperature difference from the surrounding air (around 90 degrees that day - live in Phoenix) and the hot ceramic stressed it to the point where it failed in another spot. However, on a pizza cook I don't see how I can not open the lid.

 

For as little as I do high temp cooks the ceramics are just not lasting at those temps. I do know the warranty covers replacements, but I also don't want to keep getting warranty fireboxes and heat deflectors each season either. I may just skip the pizza cooks on the KJ and see if I can get things to last longer. I just wanted to know if others have seen a correlation between failures and high heat cooks. 

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