Am I OVER-FIRING my JOTUL F-500

[DUMF]

Wowie, so many chiefs, so many experts, so many academicians.
This boys and girls is a product (wood stove)that has extreme variability in use, in performance, in real world specs, in the gross variability of fuel, and the flue construct.
Why too many of you feel a righteousness need. It is to this behavioral expert (sic) an O.C.D. in spades. You are all to go to the corner time out.
Now for a word from our sponsor.

 

[OhioBurner©]

Sootfoot, I understand where you're coming from, trying to get a credible answer. Especially after reading some of the responses, I feel like I need to offer you a beer if you were closer.

Anyhow I think the main points have been mentioned if you can sort through it all. Mainly to use larger pieces (2-3" is pretty small pieces, and will tend to burn hotter and quicker due to more exposed surface area), try shutting the stove down a little quicker, and letting the coals die down a bit more before reloading. That is if its burning too hot... I wouldn't be too worried about 850ºF on the cookplate, though I don't have a f-500 to compare notes. My Jotul 550 tends to run hot too, and would see 800+ fairly regularly on the top center if I had a full load of good wood (usually would try to keep it in the 6-700s though). I would run that insert with the air control fully closed almost all the time, my chimney just drafted a bit to strong for a low burn. I'd have installed a key damper to reduce draft but since it is a tight fitting insert the flue is not accessible for a key damper. I just replaced it with a Woodstock Ideal Steel and that can idle much lower with far better air control. The Jotul air control just did not reduce air enough. I am still however considering a key damper since in some cases the stove still can't go as low as I'd like.

 

[jetsam]

BLAZE KING... when you need a stove that controls its own air input so you don't have to mess with it or worry about overfires.

Now, back to our show!

/perfect setup, couldn't resist! =)

 

[stovelark]

To the original OP- are you getting 800 degrees on the cook plate that is the optional milled steel plate or the original stove cast iron oval plate?? 325 in the corners at that temp almost sounds like the stove had not evenly heated up yet. If indeed you have the milled steel plate installed, then those 800-900 degrees points would be probably right as opposed to the cast oval. Ideally, temps of 350-700 degrees taken from the corners of the top plate are the temps you want. Years ago with my own Oslo, I'd get up to about 450-500 or so (taking approx 45-60 mins), come back later (7-10 hrs or so), the stovetop temp had fallen back to about 200 to 250, reload and stayed warm. Great heater, blue black enamel, my favorite.....

 

[semipro]

What are normal stove plate temps when the corner reads 500F?

Interesting, the results from our burn tonight.
Oslo cranked up full speed ahead, air control wide open, temps in F:

• Upper top corner: 550
• Top cook plate: 800+ (IR thermometer maxed out)
• Front upper corner: 530

air control closed, lots of secondary action (interesting that the top portion immediately cooled when secondaries were engaged, while the front seemed to heat up.

• Upper top: corner 520
• Top cook plate 660
• Front upper corner 550

 

[begreen]

Thanks semipro, that's helpful information. I am for shutting down the stove air sooner. Less stress on the stove and longer burns. On the F400 I often had the air shut down before the stove top reached 350F. This year with the T6 I am ignoring stove top temp and going by the probe flue temp and visual condition of the fire and secondary burn. This is leading to much earlier air control closing.

 

[Sawset]

Could anyone truly define "overfire" on a cast iron wood stove. That got me curious. A quick look up of cast iron specs -
"A critical temperature in most cast iron is about 1450 degrees F. When at this temperature, conditions that can lead to cracking occur. "

 

[jotul8e2]

The current manual pdf on the USA/Canada website has a mis-print on page 8 concerning operating temperatures. There is an incomplete phrase concerning the location of the stove thermometer and so fails to describe where on the stove the temperatures are to be read. In previous versions it was made clear that the thermometer is to be placed on your choice of any of the four corners of the top.

The manual referenced above - which is written in, what, Swedish? - assuming we were given a correct translation seems to call for north-south loading (recommended firewood length of just over a foot) with very small splits of two inches in diameter or smaller. It is possible that burning small pieces of birch loaded north south will permit reloading every 80 minutes, but I am thinking you are going to have one very hot stove!

The USA/Canada manual calls for much larger logs - suggesting three to five inch diameter. Many of us can attest to the fact that an attempt to reload hardwood logs that size every 80 minutes is going to generate a fire box full of coals that will take many hours to burn down, if they ever do. Like most users here, with a full load I get maybe three hours of active burning, followed by a couple hours of good coaling. These coals will finally burn down to where few btus are generated, but will remain active enough for a restart for eight, nine, sometimes ten hours using oak, maple, or other high btu content hardwood.

My stove with my draft and my wood using my thermometer (please note all the variables here) will show an initial maximum temperature in the back right corner of 475 to 550 deg. f. It then comes down to 350 deg. f. and holds that for maybe two hours, dropping to 250 deg. after about five hours. I have a 33 foot flue with only a single slight jog, no damper, and have never had any trouble with an overdraft at any time these past seven plus years.

 

[BrotherBart]

Could anyone truly define "overfire" on a cast iron wood stove. That got me curious. A quick look up of cast iron specs -
"A critical temperature in most cast iron is about 1450 degrees F. When at this temperature, conditions that can lead to cracking occur. "

And since a surface thermometer is reporting approximately half of the internal temp then around 700 degrees stove top temp you have rung the bell.

 

[BrotherBart]

Wowie, so many chiefs, so many experts, so many academicians.
This boys and girls is a product (wood stove)that has extreme variability in use, in performance, in real world specs, in the gross variability of fuel, and the flue construct.
Why too many of you feel a righteousness need. It is to this behavioral expert (sic) an O.C.D. in spades. You are all to go to the corner time out.
Now for a word from our sponsor.

About as useless a post as I have seen in my ten years here. Congrats. Your prize is in the mail.

You misspelled the last letter of your ID.

 

[FionaD]

Perhaps this should really be a new thread... Please do move it if that's the case..

Not arguing here... Just noticing that Jotul does seem to recognise and adapt to different burning practice in different countries. See page 11 for the English language version of the European manual... Which does indeed recommend 2-3 splits for the Oslo.

(broken link removed to http://jotul.com/uk/products/wood-stoves/_attachment/2494?_download=true&_ts=1394863b90d)

As a point of interest, I realised a while back that there are several differences between US and EU jotul specs, at least on the F3, so maybe on the Oslo and other models too: for instance, the secondary air inlet is closed off by over 50% in the US F3s...that's a huge difference, isn't it? there's a US-only piece of cast iron filling in more then half of the inlet. I have often wondered (as have others here) why that is... Perhaps it's jotuls way of adapting their stoves to (what I have come to see is) the American practice of filling stoves as full as possible to get longer burn times, so that they don't over fire in the process?

Even though folk have got a wee bit hot under the collar, I've found this thread useful, as it has highlighted for me something that I've been wondering about recently ... The fact that, if I fill my stove (which also has a strong flue draft) like Americans do, the temps (and the secondaries) shoot through the roof. I am now wondering if it can't be done too well on a jotul that does not have its secondary intake half blocked off, à la American models.

My stove hits 600 stove top easily and burns well with the recommended (in European manuals) two splits.

Does all that make sense?

Given our vastly different situations, I think that advice both given and received across the pond needs to bear much in mind. I have learned almost everything I know about stoves here, and am still learning. Part of what I'm learning is that I live in scotland and my secondary inlet is over four inches wide and I need to operate my stove accordingly.

I realise this is slightly off the OPs topic - is latching on to the sub-topic - and I apologise... but I do think it's good to be aware of different countries' situations when we read and post. I agree with St Coemgen (are you Irish? Just wondering about that name) that the WWW is a global community.. That doesn't homogenise us though.. it requires us to be aware of our different situations and so on...

 

[DUMF]

Wowie, so many chiefs, so many experts, so many academicians.
This boys and girls is a product (wood stove)that has extreme variability in use, in performance, in real world specs, in the gross variability of fuel, and the flue construct.
Why too many of you feel a righteousness need. It is to this behavioral expert (sic) an O.C.D. in spades. You are all to go to the corner time out.
Now for a word from our sponsor.

About as useless a post as I have seen in my ten years here. Congrats. Your prize is in the mail.

You misspelled the last letter of your ID.

Why thank you, thank you very much. When will the prize arrive ?
No there was no "misspelling", you need to say "deleted". Now Bart get it right.

 

[semipro]

I am for shutting down the stove air sooner. Less stress on the stove and longer burns.

Agreed. I was trying to "max" things out a bit. given the OP's original questions about overheating.

 

[semipro]

To the original OP- are you getting 800 degrees on the cook plate that is the optional milled steel plate or the original stove cast iron oval plate?? .... If indeed you have the milled steel plate installed, then those 800-900 degrees points would be probably right as opposed to the cast oval.

I'm curious why you think temps would differ between the cast iron and steel cook plates?

 

[firefighterjake]

Not sure about the Oslo . . . but it sure is getting a little heated in this thread.

To get back to the OP and reiterate . . . larger wood, shut down earlier and if the draft is too much feel free to use the damper . . . and yes, the Oslo can burn for a very long time without it melting down or folks freezing to death. Happy burning!

 

[claydogg84]

Wowie, so many chiefs, so many experts, so many academicians.
This boys and girls is a product (wood stove)that has extreme variability in use, in performance, in real world specs, in the gross variability of fuel, and the flue construct.
Why too many of you feel a righteousness need. It is to this behavioral expert (sic) an O.C.D. in spades. You are all to go to the corner time out.
Now for a word from our sponsor.


Why thank you, thank you very much. When will the prize arrive ?
No there was no "misspelling", you need to say "deleted". Now Bart get it right.

Where are these new members coming from? They seem to be of less and less intelligence. It's one thing to come here to learn, but I've seen more and more of which are simply here to spread false information and be obnoxious.

 

[DUMF]

Where are these new members coming from? They seem to be of less and less intelligence. It's one thing to come here to learn, but I've seen more and more of which are simply here to spread false information and be obnoxious.

Wow, spreading the joy of knowledge, enlightenment, and warmth. Lighten up boys and girls, it's just a wood stove....then again

 

[branchburner]

small American elm 2-3" logs

-My stove top temps right now read 700-850F ** on the oval cook plate**
back corner of the stove reads 350F.
air control is fully closed, and damper on stove pipe is also fully closed.

I would call 2" a stick, not a small log... nothing wrong with burning them, but a stove full means far greater exposed surface area and therefore greater temps than normal. I'd mix them with larger logs/splits.

I don't think 800f on the center is overfire, but here's a question: what are your flue temps? If they are running high, too, it means you are heating the great outdoors more than you need to be.

Having a 500f difference between the center and the corners early in the burn makes sense, but if that difference doesn't close greatly as the burn progresses, and the air is fully shut, I's suppose the stove is leaking. Short burn times and high flue temps would tend to confirm if that is the case.

 

[stovelark]

SEMIPRO- heating up to temp, the milled steel plate will get hotter, quicker initially than the cast iron part. Eventually, I do believe the two components would equalize in temp and as the stove cooled that the steel would cool quicker than the cast. The difference in temp between the oval plate (steel or cast) is probably exasperated by more flue heat is passing by that oval part of the stove, than at the edges of the top plate as well. I guess its a lot to do about nothing, since Jotul wants the temps monitored at the corners, that's the (correct) point of measurement.

 

[heavy hammer]

As others have said maybe different scenarios might mean a little difference in burning. The members on this forum that are in the USA might be getting different results than others overseas. Claydogg84 has a valid point, saying that members here that own and burn an Oslo can comment on 8 plus hour burn times and using the Oslo for 24/7 burns with not destroying the stove. I'm not saying others might have a different reaction, but there are a lot of members who claim to be getting the same results. If not getting the same results try changing the equations to your problem. Try bigger wood try different wood, try changing your draft. Just putting my thoughts out there but if others can make it work for them, or find a way to make the stove react differently it is worth a try right? When it's all said and done everyone on this site is just trying to get the same goals, as much heat, burn times and knowledge about what ever way they are trying to heat with wood.

 

[semipro]

heating up to temp, the milled steel plate will get hotter, quicker initially than the cast iron part.

Because it it has less mass?

 

[DUMF]

Because it it has less mass?

Right, you win. That "cook plate" is thinner, less mass; meant to be replaced. It is why Oslo thermometers should be in the top corner(s).
Jotul has options for a plain plate, or a porcelain/enameled plate simply installed.
No damper needed.
Calling Jotul people.

 

[stovelark]

Well, I'm not sure. I actually thought that the steel was more dense, molecules heated faster because of that but I'm not sure. The bottom line I believe is because of where the flue gases travel up and around and toward the flue outlet that the heat is directed more intensely toward the oval plate. Especially in the heating up the stove portion of the burn. I'd need to ask Jotul engineers, I'm sure they got an explanation.....

 

[begreen]

IIRC cast iron is a bit more thermally conductive than steel but I'm not a materials engineer.

 

[semipro]

Some thermal properties of steel and cast iron from http://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html