My first "runaway"

[Pagey]

I experienced my first "runaway fire" last night. I loaded up the Endeavor pretty full with some nice, dry oak. The stovetop was reading around 350F. Within a few minutes it was 400F, and I had a nice secondary starting, so I closed the bypass damper. At 450F, I close the air about halfway, and then at 500F I set it to the "sweet spot" where I get my best burn without choking out the fire (I can't seem to get more than 15 minutes of secondary with the air control fully closed). I waited about 15 minutes, then I went to bed around 10PM. At 11PM, I woke up and noticed that the room was very warm and that I could "smell" the warmth, in a sense. I immediately checked the stove, and it was maxed out around 850F. The surface itself never became red, but the fire brick in the baffle and the burn tubes were literally red hot. I shut the air down all the way and turned on the room's ceiling fan and set it for high.

I can't think of anything that was different last night save a 15 to 20mph wind. My setup is a double wall stove pipe going up for about a 5' run, then it's 8' of Class A through a bedroom corner, possibly another 1' through the attic, and finally 4'6" on the roof. This is a straight run, no offsets/elbows.

 

[savageactor7]

Yeah Pagey, scary when that happens...seems to me some winds can pass over the chimney just right making a blow torch out of your fire. Good thing for us it very very rare. Sorry I can't recommend a good defense.

 

[Pagey]

Yeah, it was very unnerving. I just wish I could say, yes, it was the fact that the wind was up. But there's really no way to be 100% certain of that. I just found it odd that it was cruising along fine and then suddenly decided to spike like that. Makes me wonder if it has ever done that before when I've gone to bed for the night. The only other time it's done this (that I am aware of) was when I already had a nice fire rolling and I added some additional splits when the stove was already running between 550-600F. It did NOT like that, and I've made it a point to not do so again.

I suppose I should check everything out really well in the firebox tonight. But, as luck would have it, we're about to enter a cold streak for the next few days. I'll try to take some pics of the firebox and post them up to get everyone's thoughts.

 

[Chettt]

I wouldn't worry about it, stove's work 100 times better the colder it gets. Also if you're anywhere near 500 degrees, you should be able to close down the primary completely on a modern stove.

 

[karri0n]

I would just shut down the air completely when you go to bed. IIRC, most people only get 15-30 minutes of secondary burning. That doesn't necessarily mean it's not burning clean. You will produce slightly less heat, but you'll get a longer burn and have a nicer coal bed by morning with the primary all the way down.. If your sweet spot occasionally makes the stove skyrocket to 800, it's not much of a sweet spot. Perfect for daytime/monitored burning, but not overnight. Better safe than sorry.

 

[begreen]

Every loading of wood is going to be somewhat different. There will be average conditions, but no two fires are exactly alike. The "sweet spot" is going to vary somewhat with the wood and the weather conditions. As noted, when it 10 outside and blowing strong, your stove is going to draft a whole lot stronger. You didn't do anything wrong, but I think you'll find as the weather gets colder that the sweet spot will be shifting towards the fully closed position.

 

[Pagey]

The "sweet spot" I am referring to has me consistently running between 550F and 600F. Didn't mean to indicate that it caused any runaways. The only other time the stove got this hot is when I added 3 or 4 splits to an already 600F stove. Good point about the lack of secondary burn not necessarily meaning the stove is not burning clean. I need to test this during the day when I can go out and look at the chimney to check for smoke when I have the air shut all the way down.

 

[Bill]

Sounds like you have very dry, good wood. If you load a stove with allot of coals on the bottom, they tend to take off. Try dampering it down sooner and wait a while and then close the damper next time. But yes you sometimes have to keep an eye on those wood burners.

 

[T Osborn]

Just an honest question here, but does 4'6" above the roof satisfy the 10-3-2 rule? If this condition exists each time the wind kicks up, you may be having some sort of roof affect on your chimney.

 

[cannonballcobb]

Try burning fewer, larger splits the colder it gets.

When warmer outside temps return, go back to smaller splits, as the draft will be less.

 

[Pagey]

The roof has a very, very gentle slope, so I would say with 99% confidence that it does. However, being honest, I haven't been on the roof since the install. I don't have a ladder that will get me up there, and I have absolutely zero business on a roof, as I usually get vertigo when I am on one.

Looking at the picture below, the chimney would exit about even with the left side of that 2nd story window on the left. Or maybe a little to the left of the window, actually.

 

[Pagey]

Went home at lunch and took some pics inside the firebox. I did discover a large space between two fire bricks in the baffle (as you'll see). I slid the bricks into place, so that issue is fixed. My questions: do you see anything out of the ordinary? What is that gray, "wool" like substance at the back of the fire box? Also, ignore the single split lying there. I discussed this issue with the wife and we're not on the same page that in order to burn clean/hot, we need to load 3-5 decent splits per burn cycle.

Inside the box:

The evil space:

Tubes and baffle:

The "wool" like substance:

 

[karri0n]

I don't see the wool substance in the pic, but I can venture a guess... Rockwool? It's insulation.

 

[Pagey]

I don't see the wool substance in the pic, but I can venture a guess... Rockwool? It's insulation.

Look down a little and to the left of where the flashlight is shining in the last pic.

 

[karri0n]

ohhh those small flecks? Not sure.

 

[Pagey]

I've circled the area with some red:

 

[meathead]

looks like just powdery ash deposits

 

[Pagey]

looks like just powdery ash deposits

Okay. It may very well be. I'll confess that I've not poked around to see for sure. I guess I was afraid I'd mess up something royally!

 

[Chettt]

Enjoy your stove Pagey. In maybe 30 years you'll need to fix something or buy another one.

 

[Pagey]

Enjoy your stove Pagey. In maybe 30 years you'll need to fix something or buy another one.

LOL, I really do enjoy the stove. For the first time in five years, we're spending the early part of winter actually warm! I just worry about the safety of my family, and that means making sure I operate the stove properly. It really unnerved me when I came down last night to find it running so hot. I'm going to do some more experimenting this weekend during the day when I can observe the entire burn cycle and can go out and get visual confirmation of any smoke.

But, yes, by my very nature I am probably just being overly paranoid.