What happened?

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Bows & Bucks

New Member
Feb 12, 2014
11
Auburn, MI
First season burner. Super 27 without ash pan that I installed around a month ago. Have done several fires up to this point....some over nighters also. Tonight I loaded up the stove fully for the first time on a bed of coals with a stove top temp of 250 taken with my IR gun. Wood used tonight was ash with moisture reading of ~20%. After fire had taken hold and stove top temp was around 425 I started cutting air back. After less than ten minutes of running at half open air my smoke detector went off and I took a look at the pipe and could see some spillage from the flue collar. The outside temp of the double wall pipe was reading around 500 degrees. Freaked out still from this.

My stove pipe isn't perfectly level and has a jog in it at one of the seams. Guessing this may have caused the smoke spillage. Also I had been burning some wood that was not dry. I realized it wasn't dry when I heard the moisture hissing out of the splits. I have had approximately a dozen fires so far and had only been using the unseasoned wood for around 4 of those fires.

Any ideas what the heck happened? I am totally new to wood stoves and thought I had kinda figured this out. This was the first time I tried for a full firebox to get an extended burn with cold outside temps. Thanks for any replies in advance and I apologize about the long read.
 
Sure it's not the paint burning off the stove and pipe? Seems odd that smoke would spill with a warm pipe and good draft
 
That does seem odd. I am wondering if your pipe is sealed well at the joints. I mean a slight odor of smoke is one thing, but enough to make the detector go off is a whole different ball park.
 
Could be paint baking in. 500F on the outside of double-wall pipe is quite high.
 
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I had done quite a few fires up to this point and had gotten stove top temps of close to 700 so the paint curing should have been done by now.

I'm pretty sure that the pipe isn't sealed well at the flue collar. What concerns me the most is the temp of the pipe. I know the outside of double wall doesn't mean a whole lot but 500 degrees 24" up is way to high for it. Very concerned that I had a chimney fire due to the wet wood I had burned; but not sure if there would be that much creosote build up from only a few fires.

It has been around about two hours since I loaded it up and the stove top temp is still around 550 and it seems like it is cruising like it should.

Still shaken up over this.
 
Reloading dry wood on hot coals = inferno...quickly! You could have definitely cut the air back sooner. You may have burnt some junk out of the pipe too. The paint will continue curing each time you hit a new high temperature threshold. The pipe shouldn't need to be "sealed" tight because the chimney draft should be keeping negative pressure on it (air in, not smoke out) Doesn't sound like things got too outta control for ya though.
 
brenndatomu said:
Reloading dry wood on hot coals = inferno...quickly! You could have definitely cut the air back sooner. You may have burnt some junk out of the pipe too. The paint will continue curing each time you hit a new high temperature threshold. The pipe shouldn't need to be "sealed" tight because the chimney draft should be keeping negative pressure on it (air in, not smoke out) Doesn't sound like things got too outta control for ya though.
Click to expand...


So possibly the stove top temp reading hadn't caught up with what was actually going on in the firebox?

The stains in my shorts beg to differ with your statement about things getting outta control. :eek: I was about ready to tell the wife to take the kids outside.
 
Well, I would suspect that the firebox took off big time and then you had enough air going in that it was sucking flames up the flue, which lit up the creosote that was there, making the pipe even hotter, which makes the chimney draft even stronger which pulls more air into the stove, which...you know the rest...stained shorts ;lol

I'm not trying to dismiss your concern, I'm sure it was cause for a bit of tension, I just meant that in general people don't realize how much heat steel can take before there are real problems. When I built race motorcycle engines I jetted the carbs based somewhat on exhaust temp, we were shooting for 1200* or so, and that was with aluminum pistons. Carbon steel and especially stainless will take quite a bit more heat than aluminum. I guess I assume you have a proper chimney, hopefully an insulated SS liner? Proper clearances to combustibles? SS chimneys are rated for somewheres in the 2000* mark for...can't remember exactly...10-20 minutes
 
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brenndatomu said:
SS chimneys are rated for somewhere in the 2000* mark for...can remember exactly...10-20 minutes
Click to expand...

From the Simpson website:

Designed for normal, continuous operation at 1000° F flue gas
temperatures, DuraTech is subjected to rigorous and stringent HT
requirements of the UL standard, including one hour at 1400° F,
plus three ten minute chimney fire tests at 2100° F

Generally you should try to keep flue temps under 1000::F

500::F on the outside of double wall really is quite hot, I just checked mine, the inside flue temp (measured with a digital thermocouple probe) is about 580::F the outside is about 180::F( IR gun).

Stove top temp and flue temp can vary greatly, on start up with dry wood, after only a few minutes internal flue temp can be 1000::F while stove top can be only a few hundred.

Here is something I posted some time ago:

https://www.hearth.com/talk/threads...ease-from-475-to-1000-see-for-yourself.63677/

If you watch the video, flue temp goes from 475::F to 1000::F in under 3 min, while stove top temp is 100::F-200::F

IMO for best operation, you need a thermometer for the flue and the stove top.
 
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Bows & Bucks said:
I had done quite a few fires up to this point and had gotten stove top temps of close to 700 so the paint curing should have been done by now..
Click to expand...

Except the issue isn't how hot the stove had previously gotten, but how high the pipe temps had been before... and let's hope this 500f external reading had been the highest.

My stove has a different burn technology than yours, but I see incredible spikes in flue temps in early stages of the burn when the stove is getting lots of primary air (as WES999 mentions above). The stove top temps are more slow to change, so where I used to cut back air (or close my bypass damper) on the basis of stove top temps, I now pay more attention to flue temps so they don't get out of hand.

Colder/windier conditions could mean a flue is drafting more strongly than it does in warmer weather, and that stronger draft could result in higher flue temps for a given air setting over a given amount of time. So I wonder if maybe you had your air open just a little too far and/or too long for this burn, given dry wood and strong draft.
 
I have the air cut back more than half after ten minutes, from a cold start. Ten minutes after the stove had topped 400° is probably too long. I don't pay much attention to the stove temps, but go more by how the fire looks.

One of these days I'll have a probe for the double wall. I'll agree with others and say that flue temps are a better indicator than stove top.
 
I tightened a few of the screws in the pipe that had gotten loose and added a screw to one joint that was causing the slight jog in the pipe to straighten it up. I loaded about a half full load on coals again this morning and starting cutting the air back as soon as the splits were ignited. Stove top temp was around 325. I kept cutting the air back to lazy flames and waited until the fire was going good again and kept cutting it down roughly a quarter at a time. Only took around 10 minutes from first ignition to get to about half closed as jeff_t described. Once all the way cut down it cruised along at around 500 stove top temp and the outside temp of the double wall was around 200 24" up from stove. No smoke spillage yet but will be keeping an eye on this.

I will definitely be closing the air down much sooner now with the drier wood I have on hand for this winter and be looking to get a probe.

BranchBurner: it was a bit windy last night and I think that may have contributed to the stronger draft. I realize now with a full load of dry wood that the stove will not take near as long to reach operating temp and will be closing down much sooner on reloads.

Feeling much better today than I was last night for sure. Thanks to all who replied to such a newbie situation!! I have learned a ton of information from this site over the last 6 or so months and have to say it is one of the friendliest and most helpful forums I have seen.

Chris
 
Bows & Bucks said:
Begreen: what would have caused the pipe to get that hot in the first place though? Not sealed up properly? Or did I possibly wait to long to start cutting down the air?
Click to expand...
Not turning down the air soon enough is the most common cause. I now always carry a timer (or use my cell phone) and set it after starting a load unless I am going to be at the stove all the time until the air is turned down. With dry wood this can be in as little as 5 minutes, particularly on a reload. Also, try not to put a full load of wood on a large hot coal bed. That will take off very quickly and hotly.
 
Agree with others. Once you're in the 300-350 ballpark, time to cut the air back. I had quite a few brain farts last season where I let the stack (single wall) get to almost 500. When you close it at that temp, it actually goes back up a few hundred degrees before it levels back off and drops. Talk about messing up your undies! Sounds like you're getting the hang of it. There's a learning curve to every setup.
 
rudysmallfry said:
Once you're in the 300-350 ballpark, time to cut the air back
Click to expand...
I don't even wait that long. To me, it's not the stove top temp that's as important as when the secondaries are firing. By then, the flue temps are typically well above creosote level but my stove top may be less than 200. Then I'll turn it down in a few stages depending on the load, making sure the secondaries stay lit. If I keep the air full up until the stove top is over 300, then the flue temps get too high.

All that depends on the fuel quality, load size and stove design, though. Just make sure the secondaries are going and flue temp is okay before turning down and then do it stages to keep the wood burning with a "lazy" flame.

BTW, after two burning seasons, my double wall pipe still gave off some smell when it got a bit too hot (like 1000F internal). Seems like the paint on the outside never gets hot enough to fully cure for a long time on the outside of double wall. Now on season three, I haven't noticed it so far.
 
Agreed. I do it more by eye than stove top temp. You can have a blazing fire without hitting 350F yet in a cold start.
 
I have had 3 successful reloads since starting this thread by turning down the air much sooner as suggested by several people. I was initially going by stove top temps instead of just watching the fire and making adjustments based on the flame. Since I have been "reading" the fire I have been able to get the loads ignited and the air turned down so the stove cruises for several hours. Once again thanks to all who replied!
 
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