Overfire question

[heffergm]

Is it possible to overfire some internal stove part without the griddle temp surpassing 650 or so?

I ask because tonight I filled the box with some nice dry pine. I know the stove well enough at this point to know that's fine. I run it with the bypass open until the griddle temp hits about 650 to burn the glass clean. Just before I close the bypass I take a look at one of the andirons and kick me if the thing doesn't look like it was just pulled out of the forge... I'd say it was glowing red, although I suppose it's possible I was just seeing all the orange from the flames and surrounding coals reflected.

 

[jtp10181]

A little dull red glowing should be OK, I know sometimes the manifold tubes on secondry comb units can glow red. I have always heard if it starts turning, orange, yellow, or *gasp* white, then you are in trouble.

 

[LLigetfa]

My secondary tubes sometimes glow a little cherry. I have a heat diffuser above the door which is part of the air wash that has deformed from over-firing. My former RSF had the glass permanently etched from over-firing.

 

[Black Jaque Janaviac]

I've also noticed the white ash that seems to coat everything in the firebox will sometimes glow.

Of course your actual fire temps can easily exceed 1000*. But that doesn't mean that the iron/steel surfaces are that hot. So if something inside the burn box, like an andiron glows I wouldn't worry, rather just consider it a good "damper down" indicator. I think that's why the andirons and secondary manifold tubes are made to be easily replaced.

 

[Battenkiller]

Not only possible, it is common. Inside fire temps will run high enough to heat lots of parts to the visible light range. That's why many of these parts are bolted or even just hung in place. When they wear out over time through constant "overfiring", you get new replacement parts.

My old Jotul 118 clone was a hot running little beast internally. My sons and I learned to forge steel by sticking pieces of steel through the draft holes and pounding them out on a piece of railroad track. It was easy to get them bright cherry red in a minute or two. The stove itself came to me with the side baffles burned right through at the bottoms. They were the second set that the stove burned through. The buddy who gave me the stove replaced them with genuine Jotul parts and those were the trashed ones I got with the stove. I didn't want to spent the money for genuine parts, so I took two pieces of 1/4" steel plate, drilled them out and hung them in place. They lasted about two years before warping badly, and by the third year or so they were burned through and had to be replaced. This went on for about 15 years (replacing them about every three years or so), then the top baffle/smoke shelf burned through. Can't get a replacement part for that part anymore, so this year I had to stick it out in the garden and buy a new stove. That stove saw about 25 years of intense use by two people that heated entirely with it as their sole heat source. Despite all the internal "damage", it'd give another 25 years if I could find the replacement parts.

I see that there seems to be more concern among a lot of new stove owners with overfiring than with the much more dangerous situation of low-temperature burning. I can appreciate the concern after shelling out well over $2000 on a beautiful stove, but if you sized the stove properly, you will find it functions best when cranked up to hotter temps. Even the driest kiln-dried wood gives off about 60% of its dry weight in water as a product of combustion. Yes, even bone-dry firewood gives off massive amounts of water when it burns. Burning the stove at low temps allows this water to mix with the stuff you think you are burning in your secondary burn. Since these flue gases are coming into your flue pipe at temps in the low hundreds, they don't have to rise too far before they cool enough to condense onto the flue pipe walls as creosote. Then, the first time your stove runs away on you... chimney fire.

When I read that folk rarely exceed 200°F on their flue temps, I kinda cringe a bit. Both my chimney sweep and my local stove repair guys tell me to keep flue pipe temps (single-wall pipe) between 400 and 600°F measured about 18" above the collar, and I do everything I can to keep it up there. Run that puppy hot and replace the parts that get consumed over time. You bought it for all those glorious BTUs you could get out of it. Burn it like it was designed to to burned and keep your sweetie toasty warm... and safe from chimney fires.

 

[cycloxer]

Yes. I have seen the rear of my secondary burn assembly glow a very dull red. I have also seen the front air deflector glow a dull red. I only noticed the burn assembly glowing when I had the firebox roaring and I dimmed the lights.

When you get the exterior castings or plate of your stove to glow, that is when you can really start to have problems.