cast iron... how hot is too hot?

I endeavor to keep my stovetop temps in the 400 - 600 range when cruising, and always below 700F when getting ready to engage the catalyst. I did once see over 700F on one of my Condar magnetic stovetop thermo's, maybe 740'ish if I had to guess (it's only marked to 700F), but my IR gun read 699 on that location. Made me nervous, as the stove top was pinging more than I'm used to hearing, but I suspect the stove was no where near any level of self-destruction.

I carefully read the Jotul manuals for my old Firelight 12, and there's no mention of stove-top temperatures, recommended or maximum. So, I pulled up the new manuals for the Firelight 600, and found recommended ranges for cruising efficiency, but again no maximum temperature listed. What should one assume as a max safe temperature for cast iron?

Its been mentioned in the past that 900 is the threshold where cast starts to glow a deep red. The manual for mine lists 750 as the limit for regular operation, I believe this is a typical figure.

Cool. Thanks guys! I figured this was the range, but wanted to make sure I had my head on straight.

I think the F600 manual says to measure stove temp in one of the back corners, but I'm finding that the temp in the middle of the top can be a couple hundred degrees higher on the Firelight12. Any comments if you're seeing something similar, and if so how to properly determine operating temp?

Yep. The F600 does not have a top-load door, as it's hindered by the reburn system under the lid.

Measured in the center of the top-load door, I cruise the Firelight 12 at 350 - 550F most of the time. This week, being insanely F'ing cold outside, I'm running 450 - 650F in the center of the top-load door. To get the cat to light off, I burn wide open to 500F, then half open to 550F, then 1/4 open to 600F, then almost fully shut, until the wood is finally charred enough to get the cat to light off. On a large load of my less than optimally seasoned wood, I'm sometimes at or near 700F on that top load door, before the cat will take off, even with the air control shut almost completely.

For a while, I had moved the magnetic thermo to the front corner of the stove, very close to the raised oval for the top-load door, and there I was running about 200F cooler than the numbers above.

The center of the top on the F600 is always hotter than the corners as the flames are passing by at that location. The manual states to take the temps at the corners, so that is where I have placed my thermometer and also where I shoot the IR thermometer. I have to assume Jotul is aware the center will be hotter.

True, and perhaps useful, if Jotul specified a max temperature to measure in the corners! I'll admit I did not read the F600 manual as carefully as I did the F12, but I did not see any mention of an absolute maximum safe temperature, in either manual.

No, there is no mention of a max temp, just operating temps of 400-600. I find mine likes to cruise around 625-650, which does not concern me.

I guess the obvious flip-side to this question is:

What's the hottest you've ever had a cast-iron stove. What damage was incurred?

Wow...I never see anything that hot. I see about 600 on my cast around the collar, and that's pushing it.

Last night, I inadvertently let my Oslo go to 700. No damage, although I try to keep it below 600. I have a magnetic thermometer in each front corner. My biggest issue with running it hot is that it chews through wood like crazy! On nights down around zero like we've been having this week, that's OK.

Yeah, sort of meant for those times when someone walks away from a stove when it's in bypass or wide open, and loses track of time... not how hot do you like to run your stove!

Pegged the needle at 900* once. No damage and no red glow either. Got it under 700 quick after I shut air down. I was worried though I must say.
Cause, too many small splits. This was many years ago ,never past 800 since

I've had 800 degree temps on parts of the old Vigilant. The front doors would get particularly hot at times as the stove did not have andirons and the wood would rest up against the doors.

I had parts of the front door glowing red on two-three occasions, but that was before I had an IR gun, and the glowing was not intentional on my part.

On the Defiant, I have had the griddle up to 750.

Had my 1987 Encore up to 800 a few times and the lower fireback cracked years back so I replaced it.
Last year I managed to let it hit 800 a few times again my mistake and the fireback is again needing replaced.
This time I want to replace the upper and lower fireback as well as the refractory and cat.
Both upper and lower are warped a bit and lower has vertical cracks.
Gonna cost me about 700 but I will do it rather than replace it cause I am just stubborn

Installed ss 8 inch liner 3 years ago and the draft is very strong so I have to watch when reloading from just ashes. I installed a probe in pipe just above the T and it has reached 1400 twice and pipe glowed RED.so I again have to watch when reloading and not run air wide open for morethan 2 or 3 minutes

We just ordered the 'inferno' stovetop thermometer to keep an eye on our insert. I've seen some good threads on here as to where to position the thermometer on the Jotul C450, but for now I have been going by the sound of it ticking and the rate at which I burn the hair off my hands and forearms

http://www.sizes.com/materls/colors_of_heated_metals.htm

The upper left shoulder (the business end of this stove's secondary burn system) on our 2008 VC Encore 2550 cat stove got 830 f. once. Scary. It also routinely has the exhaust hood (rear wall of the firebox) accidently glow dull red no matter how I try to avoid the glow. So far no seeming ill effects (warpage) because the hood still goes on and off OK.

Hit 700 once...the tubes were glowing like red lights on a christmas tree

This is making me feel much better about hitting 740F once, not something I aim to repeat, but knowing its bound to happen someday. In my case, it was when I had one stove getting warming up in bypass mode, and I was busy loading the second.

The highest I've ever seen on the griddle thermometer was 700, maybe once. You really have to push this stove hard to get that temp without something else getting way too hot first.

On a regular basis I will get the andirons inside the stove hot enough to glow (900+) when firing a new load since they pretty much sit in the coal bed. I imagine the ash grate probably gets just as hot. On a couple of occasions I have had the glowing combustor throat issue like Gark but this always was accompanied by a cat over temp ( 1800+) so I know what to watch for.