Overfire Protocol

[Chuck the Canuck]

Howdy. Hope ya'll had a great New Year's Eve! I brought in the new year babysitting my stove as it went semi-nuclear and inched ever closer towards a full blown overfire situation. The scenario:

So I followed the same routine as I always do for an overnight reload; burned down the coals from the evening fire (stove top was at about 140F or so but there were for sure still some pretty hot looking good sized coals in the bed of the stove) and loaded up the stove with 6 medium/large sticks. After about 10 minutes the stove got to about 450F stove top and I cut the air down to half and then shut it down completely a couple of minutes later when the stove top hit around 520 or 550F, knowing that the temp would keep climbing until it levelled off around 675 - 720F like it usually does (the flue thermometer was reading around 320F when I shut the air completely down). Anyway, it never levelled off and kept climbing and climbing and climbing. The primary air wasn't doing much, with lazy flames down low and at the sides (at least for the first hour or so) but the secondaries built into a total raging inferno.... I had a fan running full speed over the stove after it hit 750F on the stove top, but even so it reached around 820 - 830F in the middle section of the stove top around the flue, and hovered around 680-720F around the outer edges of the stove top for a good couple of hours... Needless to say, although it all started off with raging secondaries, eventually the whole firebox came to resemble a raging inferno after about the first hour. The flue temperature stayed pretty constant at around 350F, but I suspect that the fan had something to do with that....

So why would I get a raging inferno even though I shut down the air completely, and nice and early in the burn to boot??? Leaky door gasket maybe? I checked the gasket on the door this morning and it looks a bit thin & flimsy on the 2 bottom corners, and very questionable where the two ends meet at the bottom middle of the door (like an extra 1/8" to 1/4" of gasket would have made a better seal, maybe...).

So I was reading another thread "How do you guy's cool the stove with overfire" and it seems that I should just open the door next time? My question is, do you just leave the air damper closed and then slowly open the door??? I better go check on the stove...

 

[Chuck the Canuck]

As an addendum to the above post, the stove seems to be burning fine this morning with normal secondaries.... although I did shut the air down a bit quicker than usual this morning and I've got stove top temps around 520F, single wall flue surface temp 300F at 18" above the collar. I noticed last night and again this morning that sometimes the left side of the stove top is hotter than the right side... does this indicate air leakage or is it just a normal quirk? Sometimes both sides run together in almost perfect harmony too....

 

[tcassavaugh]

knock wood....I haven't had a bad over fire. well, not one that has happened because of a stove failure although I have left the stove controls open trying to start a fire and walked away once or twice. byt the time I got back, the stovepipe temp was up in the top end of red but shutting it down or closing the main air and key damper brought it under control. last time it started climbing, I had a bad stove gasket. I saw the recent threads about opening the door, prettymuch letting it act as a fire place. I hadn't heard of that before but it makes sense. me, being "figuratively" from Missouri had to try it and see how it worked. After my stove had got running along, but not hot, I opened up the door......it calmed right down and behaved nicely so I would think it would probably work. good advice that you wouldn't think about. good luck in finding the cause. hopefully, its just a air control or gasket problem that's easily fixed.

 

[DougA]

I am confused. "The flue temperature stayed pretty constant at around 350F" but at the same time " it reached around 820 - 830F in the middle section of the stove top around the flue"
When my stove reaches 800, I don't need a thermometer to tell it's crazy hot but the flue temps will always be very high also. Perhaps the design of my stove is very different from yours.

I'm wondering if one of your thermometers needs a tap (or more). I've even had my digital probe go ballistic a few times. I pull the 110 v plug, push it back in and the temps are suddenly normal again. Could be?

 

[DougA]

knock wood....I haven't had a bad over fire. well, not one that has happened because of a stove failure although I have left the stove controls open trying to start a fire and walked away once or twice. byt the time I got back, the stovepipe temp was up in the top end of red but shutting it down or closing the main air and key damper brought it under control. last time it started climbing, I had a bad stove gasket. I saw the recent threads about opening the door, prettymuch letting it act as a fire place. I hadn't heard of that before but it makes sense. me, being "figuratively" from Missouri had to try it and see how it worked. After my stove had got running along, but not hot, I opened up the door......it calmed right down and behaved nicely so I would think it would probably work. good advice that you wouldn't think about. good luck in finding the cause. hopefully, its just a air control or gasket problem that's easily fixed.

It depends. If you have mostly kindling or small sticks, I would never open the door because you are adding oxygen to an inferno. If you have mostly larger sticks, then yes, opening the doors should actually cool things down. I have not done that but it makes sense. I'm not sure that is something you could feel comfortable in doing or even remembering in an emergency but it's the same as gently accelerating when a front wheel drive car is skidding on a snowy street. You want the front wheels to pull you into control, not lock-up. Also that takes a few times to practice before you can believe in it.

 

[Chuck the Canuck]

I'm wondering if one of your thermometers needs a tap (or more).

Yeah, I wondered about that last night. I have a magnetic therm on the flue and an IR gun, and when I double checked the IR gun up on the flue it was almost dead on with the magnetic therm..... 800F was mainly around the middle area of the stove top, with 680-720F around the outer edges of the stove top, using the IR gun. The left side of the stove top was running hotter by around 30F, so if it was 830F on the left middle stove top, it was around 800F on the right middle stove top, and so on.... The flue thermometer was inching up towards 400F when I turned on the fan, and that brought the surface temp of the flue down pretty handy to around 300-325F, but come to think of it I'm pretty darn sure that the flue gas temp must a been a whole lot hotter; it was probably at least 800F if not higher during the peak inferno period.....

 

[Chuck the Canuck]

I thought of opening the door last night, because I was sure I'd read about doing that before. But, I couldn't come upstairs and start searching Hearth.com to find the relevant post because I didn't want to walk away from the inferno (I just kept moving the fan around and inch this way, and inch that way, lift it in the air and focus on the stove top, read temps with IR gun at 500 stove top locations, repeat repeat repeat........

 

[Chuck the Canuck]

I also thought of opening the door and throwing a shovel full of ashes in on the fire, but I opted to monitor the situation endlessly instead....

 

[Chuck the Canuck]

Here's the stove at present with 6 medium logs loaded: air shut down completely, surface flue temp around 310F, left middle stove top 626F, right middle stove top 636F.....

 

[Chuck the Canuck]

You notice how the fire is burning with a lot more flame on the right side of the stove in the picture above? Last night the situation was reversed, and there was a noticeably higher amount of flaming on the left side of the stove??? I don't know what the heck this stove is trying to say to me.....

 

[tcassavaugh]

I, rely more on my exhaust temps than my stove temps. I know some will probably chastise me for it but I figure that if you take care of the exhaust, the stove will take care of itself. I keep it in the 350-450 range most of the time and my stove runs pretty well. looks like you have some good secondary's going there. doesn't look too out of the ordinary to me but i'm not familiar with that stove.

 

[Chuck the Canuck]

Well she peaked a few minutes ago at around 680F stove top (flue therm never budged over 320F) and then started drifting slowly back down towards the low 600's, which is where I'm comfortable.... But it seems like there's an awful lot of flaming going on in that firebox for a stove with the air shut down completely. Our outside temps last night and this morning are hovering around 18C (around 0F); do you suppose that is causing my draft to go a lot stonger, thus leading to raging secondaries??? Or perhaps I loaded the overnight load to early and just needed to burn down the coals a while longer maybe.......

 

[Chuck the Canuck]

But looking on the bright side, the house is toasty warm, the heat pump ain't come one once since I started burning last night when I got home, and the wife is making cookies to go with our New Year's dinner, so.... Happy New Year's ya'll........

 

[tcassavaugh]

But looking on the bright side, the house is toasty warm, the heat pump ain't come one once since I started burning last night when I got home, and the wife is making cookies to go with our New Year's dinner, so.... Happy New Year's ya'll........

Happy New Year to you and yours also......
those secondary's get rolling on my stove when I shut the air down too....I think its part of the design. they roll for five or 10 minutes then they kind of spurt or get occasional secondary "flares" and that's when I increase the air a bit to nudge the stove into burning again rather than smoldering. temps might have had something to do with it....my stove prefers it cold but that's relative and below 30 degrees, not 0 F. we don't hit those temps too often. enjoy the cookies.

 

[Brick (ware)House]

I hadn't heard of that before but it makes sense. me, being "figuratively" from Missouri had to try it and see how it worked. After my stove had got running along, but not hot, I opened up the door......it calmed right down and behaved nicely so I would think it would probably work. good advice that you wouldn't think about.

"I come from a country that raises corn and cotton, cockleburs and Democrats, and frothy eloquence neither convinces nor satisfies me. I'm from Missouri, and you have got to show me."

Never had my stove top over 620 but I need to test the open door technique myself just in case.

 

[Sully]

Open door works perfect. Did the other night. Had to stove went way hot, about ten min I left door wide open and it had gone down significant. 300 or so. I tried wet paper that just dried up and burnt in about a min , door was key to cool down

 

[begreen]

Chuck, you did the right thing. Get a fan on it and by all means, stay calm and observe rather than over-reacting. Opening the door has worked for me in the past when I had a rare too intense bloom of fire. It reduces the blaze quite quickly as it cuts off draft from the secondaries.
FWIW, this was always my fault, typically from loading very dry wood on a very hot, deep coal bed. Now I always burn down the coal bed to a reasonable level first.

 

[Chuck the Canuck]

FWIW, this was always my fault, typically from loading very dry wood on a very hot, deep coal bed. Now I always burn down the coal bed to a reasonable level first.

Yep. I suspect that I did this too.... hopefully I've learned my lesson and won't repeat the same mistake again (at least not too soon)....

Thanks to everyone for the feedback. I really do appreciate the enormous amount of wisdom that is so freely shared on this site.

Cheers,

 

[BrotherBart]

I was having sympathy pains for ya last night. About the same time the 30-NC was at around 800 and not looking like it was getting sleepy. Decided I have a new spare one in the basement if it split down the middle and just rode it out.

 

[Chuck the Canuck]

So having sweated my way through this escapade, is 830F stove top considered an overfire situation? Is there any danger of damaging the steel on the stove, or damage the gasket around the door or anything like that?

 

[HotCoals]

So having sweated my way through this escapade, is 830F stove top considered an overfire situation? Is there any danger of damaging the steel on the stove, or damage the gasket around the door or anything like that?

That's getting pretty dang hot!

You're not going to melt that steel,maybe warp something or pop a weld with the steel wanting to expand.
830 outside the box could be double that inside it.

 

[BrotherBart]

You're not going to melt that steel,maybe warp something or pop a weld with the steel wanting to expand.
830 outside the box could be double that inside it.

The UL clearance testing is at around 1400F surface temp.

 

[HotCoals]

The UL clearance testing is at around 1400F surface temp.

WOW..never would have thought!

 

[BrotherBart]

They feed the thing firebrands made of these stapled together and get it as hot as they can.

 

[Chuck the Canuck]

The UL clearance testing is at around 1400F surface temp.

So I guess I'm good to go eh???