Overfiring is heating your stove up too hot to the point of damaging it.

To me, over-firing or too hot, relates to heating the stove and/or chimney to a temperature which starts to advance into the failure safety zone of each. Thus, it depends on the design of each.

In practical terms, for my wood stove, firebrick lined, standard black chimney pipe to ceiling, and insulated stainless chimney above, over-firing or too hot is when 900-1000F internal flue temp is achieved, although my typical burn will have internal flue temp of 550-800. My understanding is that the stainless chimney operating design is 1000F, about 1/2 of its design failure range. In other words, it is designed to take a 2000F chimney fire for a period of time before failing.

Stove/chimney thermometers are not known for their precise accuracy but they do provide good relative info. In general, as a rule of thumb my understanding is that if the temperature of the external black stove pipe at the point of measurement is X, then internal flue temp is 2X at that point.

As mentioned my typical burn will have internal flue temp of 550-800, external flue temp 275-400. At about the low end of this range my stove has heated well, and secondary burn will sustain. The real sweet spot for my stove is external flue temp of 300-350, which I seek to obtain with an appropriate air setting. At this temp I can throw in one split at at time when the prior one has burned to large coals, temperature will be maintained, and I don’t much need to attend to the stove at all.

Hotter burns for a radiant heating stove produce disproportionately more heat, by about a factor of 4. See:
http://www.hearth.com/econtent/index.php/forums/viewthread/15043/
So, I guess this means that if you need the heat, burn hotter within the design range of the stove/chimney.

As to starting your stove, getting a fire hot quickly is also what I do. A slow start produces lots of unburned gases, potential creosote, so I want to get up to heat as soon as possible and get the secondary burn well started. Also, slow, low temp burns I avoid for the same reason, except when the wood has burned all to coals. At that point creosote formation possibility is minimal.

over-firing or too hot is when 900-1000F internal flue temp is achieved,

Routinely over firing a metal stove will cause damage by warping the iron or steel, making welded joints open and leak as well as increase risk of fire in your home.

Although specific temperatures for over firing vary with different models, ball park figures are over 900* F for an extended period.  Rather than worry about where the stove may be too hot, if any part of it, usually the collar at the base of the flue, begins to glow red, this means the metal has reached an approximate temperature of around 900* F which most feel is a sign of over firing.

Aye,
Marty

If you have a clean burning stove, there is little need to intentionally fire it way up to burn off the creosote. It should be burning off constantly (secondary burn).

In general, over firing should not occur with normal wood and the normal air control settings on a stove. The air controls are limited as to how much air they allow to enter, which keeps the temp at ‘design’ specs.

However, burning construction lumber, dunnage, packing, and other such stuff...can over fire a stove. So can leaving the ash pan or loading door open for two long. Ideally, most steel and cast stoves would be kept below 800 or 850 degrees on the hottest part of a single wall top surface - 700 is just about perfect. But a couple forays into hotter territory is quite normal with many stoves. I know that many models I burned often floored the thermometer for a few minutes. A properly designed and built stove should have no problem with occasional hotter temps. However, a stove used in this fashion constantly may need premature parts replacement.

Thank-you all for the definition.  That is what I thought it was until I read something about it happening at a start up. 

We are hopefully getting our Jotul 550 installed on Monday and I want my facts straight...( Kids and husband have the flu so I’m praying I don’t get it too or else we can’t it installed until I’m well.  Will probably have to hold off on the curing process due to the fumes...give them a chance to recover.)

Many people talk about temps on the flues.  The 550 is an insert so I will be using an external thermometer (Rutland) which I know aren’t too accurate but will give me a ball park figure.  The salesperson at the store I bought my stove at has no clue to what max. temp is for this insert.  Manual simply states not to over fire the unit but gives no temps… I’m assuming I can go up to 700 for awhile and be okay.  How do I find out temps okay with this unit?

In the insert I have now I usually burn up at 575 for awhile and then sit at 400 for most of the burn and our house, on a day above 40, will stay at an okay temp.  I am getting the Jotul in hopes that on colder days (below 40) we can maintain warmer temps than with my current unit.  I’m assuming I’ll have to get it up over 575 to achieve that.  I guess I will soon find out as the unit breaks me in!

“How do I find out temps okay with this unit?”

When you see red, stop.

Aye, Marty

Marty - I don’t want to see red at all on account of I don’t want to cause damage to the insert.  When you say “seeing red” do you mean on the flue?  The Jotul I am having installed is an insert and has a cast iron surround that covers up the flue so the only thing I would be able to see turning red would be the door/exterior of the insert itself.

I get scared if the temps go above 600* (external door temp) I can’t imagine what would happen to my heart rate if any part of my insert would turn red.  I would probably faint and miss the whole show!!!!

perplexed - 09 February 2008 06:20 PM

Marty - I don’t want to see red at all on account of I don’t want to cause damage to the insert.  When you say “seeing red” do you mean on the flue?  The Jotul I am having installed is an insert and has a cast iron surround that covers up the flue so the only thing I would be able to see turning red would be the door/exterior of the insert itself.

I get scared if the temps go above 600* (external door temp) I can’t imagine what would happen to my heart rate if any part of my insert would turn red.  I would probably faint and miss the whole show!!!!

    I thought I was the only one on here like that....nice to know I have some company!!!

The secondary tubes on my Quad glow often. When the top of the fire box glows red, I get scared - it’s happened 3 times with no noticeable damage. My IR thermometer registered 950 at the red steel- ouch! On my insert this only happens with a well established fire, and the air turned way down - with VERY strong secondaries. It’s the secondaries tickling the top of the box that do it.
Ways to avoid it:
Use less wood
Pack the wood tighter so air cannot freely circulate
Learn how to adjust air to keep your fire under control - varies from stove to stove.

Read my lips:

Seeing red* = over firing = PO’d (metal) = NG (no good).

Aye,
Marty

*anywhere on your metal stove except the firebox

PS:  My Harman TCL 2000 is cookin’ now with a belly full of anthracite.  It’s in my basement (68* F) and I’m writing this in my office on the mainfloor (70* F).  Outside now it’s about 4* F, with a steady 25 mph wind out of the NW gusting to 45 mph.  Wind chill somewhere around -35* F.  Guess I’ll have that second cup of coffee now and plow the road after it lets up…

OK fokes if I think I am overfireing . New DW , 2 small break in in June , How do I stop it Less air or more to cool , .At my ex gf s house her regency insert pipes glowed all the time

The secondary air tubes getting hot is not a big deal.

As for the beginning of the fire… are you sure that you aren’t talking about break-in fires?  The first few fires in a new stove should be smaller, shorter fires during break in.

Was asking how to stop it .  Havent even had mine to 300 degres yet to small breakins so far waitting for cooler weather

Can anyone tell me what temp is ideal for mt Jotul F400 castein single door?? I’m looking for the temp where you are not to cold or to hot.

thanks john

johnnywarm - 24 August 2008 05:22 PM

Can anyone tell me what temp is ideal for mt Jotul F400 castein single door?? I’m looking for the temp where you are not to cold or to hot.

thanks john

Jotul says that the Castine is most efficicent between 400 and 600 degrees stove top temperature. It should be on page 8 of your manual.

BrotherBart - 24 August 2008 06:16 PM

johnnywarm - 24 August 2008 05:22 PM

Can anyone tell me what temp is ideal for mt Jotul F400 castein single door?? I’m looking for the temp where you are not to cold or to hot.

thanks john

Jotul says that the Castine is most efficicent between 400 and 600 degrees stove top temperature. It should be on page 8 of your manual.

Thanks BB. I only seen the brake in part.

I have found that calling the manufacturer can clear up any questions you have. They don’t post all information in the manual.

As far as parts getting red hot, my Dutchwest cat stove has a iron grate of sorts below the cat chamber (allows hot gasses access to the cat chamber). When that cat was lit the grate would glow cherry red and there was no way around it as this happened every time you had a good fire going. Point is each stove is different.

You will know you are over-firing when you hear that sound of the “freight train” rumbling thru the room the stove is in.