# cast iron... how hot is too hot?



## Ashful (Jan 25, 2013)

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?


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## pen (Jan 25, 2013)

I'd say you are AT the redline for what you'd want to see if you want the stove to last.


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## jharkin (Jan 25, 2013)

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.


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## Ashful (Jan 25, 2013)

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


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## Jags (Jan 25, 2013)

740 didn't hurt that cast.  Burn on, Brother.


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## Bluerubi (Jan 25, 2013)

Joful said:


> 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?


 
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?


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## Ashful (Jan 25, 2013)

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.


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## remkel (Jan 25, 2013)

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.


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## Ashful (Jan 25, 2013)

remkel said:


> 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.


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## remkel (Jan 25, 2013)

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.


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## Ashful (Jan 25, 2013)

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?*


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## begreen (Jan 25, 2013)

Joful said:


> 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?*


 
Does that include underwear?


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## firecracker_77 (Jan 25, 2013)

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


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## clr8ter (Jan 25, 2013)

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.


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## Ashful (Jan 25, 2013)

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!


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## adrpga498 (Jan 26, 2013)

Joful said:


> 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


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## BrowningBAR (Jan 26, 2013)

Joful said:


> 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?*


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.


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## Excavator (Jan 26, 2013)

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


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## TheBaron (Jan 26, 2013)

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


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## Dune (Jan 26, 2013)

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


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## Gark (Jan 26, 2013)

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.


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## ArsenalDon (Jan 26, 2013)

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


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## Jags (Jan 28, 2013)

I have peaked at 900F.  Quickly brought it down to 700 (when I realized I screwed up, ash pan was not secured properly).  No worse for the wear.


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## Ashful (Jan 28, 2013)

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.


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## jharkin (Jan 28, 2013)

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.


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## firecracker_77 (Jan 29, 2013)

Jags said:


> I have peaked at 900F. Quickly brought it down to 700 (when I realized I screwed up, ash pan was not secured properly). No worse for the wear.


 
That stove you have is a beast.  I've been watching your posts for some time and it sounds like she gets hot very quickly and throws alot of heat.


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## firecracker_77 (Jan 29, 2013)

jharkin said:


> 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.


 
I like that house of yours.  The fact that you have 3 woodburning areas is pretty cool.


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## Jags (Jan 29, 2013)

firecracker_77 said:


> That stove you have is a beast. I've been watching your posts for some time and it sounds like she gets hot very quickly and throws alot of heat.


 
I am lucky that it is built like a tank.  I am not the kindest person to it.
But - I have always said that the IR is one of the easiest breathing stoves that I am aware of.  Its a 3.0 cuft cast iron stove that was built with one thing in mind.  Make heat.  It does that pretty darn well.  I am also running very good (read dry) wood.  All this said...it is also a very controllable stove with one exception.  It don't do slow and low very well. It likes to cruise at 550-650F.


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## tfdchief (Jan 29, 2013)

First, this is not an effort to try to answer your question,  You have gotten good answers already.  Just an interesting part of my past. 
My Uncle heated his shop with a large old pot belly stove.  He was a carpenter and had lots of scrap lumber.  That is the only thing he ever burned in that old stove, and it always had some part glowing red   I thought you were supposed to run them that way


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## BrowningBAR (Jan 29, 2013)

firecracker_77 said:


> I like that house of yours. The fact that you have 3 woodburning areas is pretty cool.


Dear god, I long for a centrally located chimney in an open layout...


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## Ashful (Jan 29, 2013)

BrowningBAR said:


> Dear god, I long for a centrally located chimney in an open layout...


 
Amen.  The novelty of running multiple stoves wears off very fast, particularly when you have a tight work schedule, kids to get to bed in the evening, etc.


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## jharkin (Jan 29, 2013)

Everything is relative. I have a not horrible heating layout as old houses go... But I long for a second bath. I long for actual closets. I long for not hitting my head on the stairwell header. I long for a basement that doesn't require walking around like a hunchback to clear the pipes.  I long for space to put the kids toys somewhere other than the living room. I long for more than 3 ft of kitchen counter.


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## firecracker_77 (Jan 31, 2013)

BrowningBAR said:


> Dear god, I long for a centrally located chimney in an open layout...


 
I know that it's more work but still...it is nice to have a bunch of fireplaces...whether it's easy to keep them going...you would be the resident experts on these matters


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## firecracker_77 (Jan 31, 2013)

Jags said:


> I am lucky that it is built like a tank. I am not the kindest person to it.
> But - I have always said that the IR is one of the easiest breathing stoves that I am aware of. Its a 3.0 cuft cast iron stove that was built with one thing in mind. Make heat. It does that pretty darn well. I am also running very good (read dry) wood. All this said...it is also a very controllable stove with one exception. It don't do slow and low very well. It likes to cruise at 550-650F.


 
Sounds good.  3 cubic feet should be overnight burn range  As long as she isn't smoking the wood like cigarettes!


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## Jags (Jan 31, 2013)

firecracker_77 said:


> Sounds good. 3 cubic feet should be overnight burn range As long as she isn't smoking the wood like cigarettes!


 
I can do an 8 hours burn and end up with a stove top of about 300F.  Easy restart.  My problem is that I am often away from home for 11 or more hours any given day.


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## BrowningBAR (Jan 31, 2013)

firecracker_77 said:


> I know that it's more work but still...it is nice to have a bunch of fireplaces...whether it's easy to keep them going...you would be the resident experts on these matters


It's easier than it has ever been now that I have the large stoves in place. But, it is still a lot of work.


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