Loud banging in stove pipe, chimney fire?

[Dug8498]

Slightly embarrassed to ask this, but I'd like some feedback.... was watching TV with the wife and heard a loud banging coming from above us. We heard a total of maybe 4-5 loud bangs over the span of 5-10 min. It startled us both and I want outside to see if a tree branch had landed on the house or something. After finding nothing I am thinking it must have been the stove pipe. Did I have a chimney fire? There was no jet engine wooshing sound that others have talked about.

When I was outside, I didn't see anything crazy coming from out of my stack, just normal minimal white smoke. stove temps were around 650 and magnetic flue thermometer was reading high, close to maxed out, flue damper was completely closed. So I'm not sure how I was getting temps that high with damper completely closed and air about 1/8 open.

I burned wet wood last winter for about 3 months as that's all I had access to so I'm sure I had some creosote buildup. I have a chimney sweep scheduled to come in two days but I have a feeling it'll be rescheduled out a week or two due to rain in the forecast. I was hoping to not burn before the sweep came, but it's been cold so I figured I could get away with doing a few fires.

New stainless steel 6" liner was installed last November. Should I hold off on burning until I can get it swept and inspected? I plan on doing a visual inspection of the liner today when I get home from work. Any suggestions on what to look for?

 

[weatherguy]

Was it windy out? Maybe a branch banging

 

[Dug8498]

Was it windy out? Maybe a branch banging

It was a bit windy but nothing crazy, but I walked all around the house and didn't see any evidence of that. We don't have any trees overhanging the house, so I'm not sure how that would have happened.

 

[begreen]

Was the fire banked down quite a bit? Is it possible the sound came from the stove? How dry is the wood this year?

 

[Dug8498]

Was the fire banked down quite a bit? Is it possible the sound came from the stove?

Begreen,

The fire was cranking pretty good. What does banked down quite a bit mean? The air was open maybe 1/8th and the flu damper was and had been completely closed for a while. I had just thrown in a bunch of splits

It definitely wasn't the stove. I'm not sure what my Jotul F118 is made of, but it makes all sorts of noise when it's heating up. This sounded like it came from higher up in the stove pipe. I am concerned because i went on the CSIA website (https://www.csia.org/chimneyfires.html) and it mentions "loud cracking or popping noise" as one of the indicators. That's how I would describe this. Not the normal crackling/expanding contracting noises I will hear from the stove and the stove pipe immediately off of the stove.

 

[Ludlow]

The hot temps could have made the liner expand and bang off the side of the chimney maybe?

 

[begreen]

OK, what I was wondering was if there was a delayed combustion of unburnt wood gases. If wood is not well seasoned and the air is closed down too much, the flames can go out for a moment, but the wood is still hot and off-gassing (smoking). Eventually a flame reignites on the wood and when it does it ignites all the unburnt wood gases. This causes a mini-explosion or puffback. That is just a guess.

Moving thread to the Classics Forum for the F118.

 

[charger4406]

I've had a chimney fire a couple of times. and the sound they made was like a constant freight train roaring through the pipe,
never had any loud banging, if you hear it again just go out and look at the top chimney, if it's a fire you should see
flames out the top.

 

[Ludlow]

A backfire (not unlike a lawnmower) in essence?

 

[Dug8498]

OK, what I was wondering was if there was a delayed combustion of unburnt wood gases. If wood is not well seasoned and the air is closed down too much, the flames can go out for a moment, but the wood is still hot an off gassing (smoking). Eventually the flame reignites on the wood and when it does it ignites all the unburnt wood gases. This causes a mini-explosion or puffback. That is just a guess.

Moving thread to the Classics Forum for the F118.

Whoops, sorry put this in the wrong spot.

It's a possibility, but I do know my wood all measures 22% or below (most splits measure around 17%) and isn't hissing or smoking at all as my wood did last winter. Definitely a possibility though. If this noise did come from the stove pipe should I be worried? Can I continue to burn if all passes a quick visual inspection later and the liner doesn't look warped etc?

 

[Dug8498]

A backfire (not unlike a lawnmower) in essence?

Exactly. Loud. Bang.

 

[begreen]

Like I said, just a guess. If the sweep finds no issues it should be ok to burn. How long has the liner been in and was the chimney completely and thoroughly cleaned before it was installed?

 

[Dug8498]

I've had a chimney fire a couple of times. and the sound they made was like a constant freight train roaring through the pipe,
never had any loud banging, if you hear it again just go out and look at the top chimney, if it's a fire you should see
flames out the top.

Appreciate your input. I was asking as I showed very hot flue flue temps and heard the banging, but I didn't see any of the other tell tale signs of an overfire like glowing pipes, the roaring, flames out the top etc. My chimney cap looks fine, from what I can tell from the ground. I dont love heights, but I'm considering sucking it up and climbing up there

 

[begreen]

What kind of flue temps and how are they being measured (surface or probe thermometer?)

 

[Dug8498]

Like I said, just a guess. If the sweep finds no issues it should be ok to burn. How long has the liner been in and was the chimney completely and thoroughly cleaned before it was installed?

So we bought this house in January. The previous owner was required as part of the sale to have a sweep come out and inspect everything. The sweep found that the liner was "warped due to chimney fire". They installed a brand new stainless steel 6" liner in late November (the sale took another few months to complete). I unfortunately don't know if it was cleaned before it was installed as I wasn't there for that. I hope so!

Alright, I was hoping to not have to wait for the sweep to come as that may be another week; all sweeps are booked up right now. Thanks!

 

[begreen]

If the flue temps are excessively hot something is not right. Is there a key damper on the stove pipe? Here is another wild guess. Creosote flakes have dropped down to the bottom of the tee (at the thimble) and collected. Excessively hot flue gases are causing them to smolder and eventually ignite.

 

[Dug8498]

What kind of flue temps and how are they being measured (surface or probe thermometer?)

It's a single wall pipe coming off of my stove so I have a magnetic flu thermometer (can I put a probe thermometer on single wall pipe?)

Usually the flue temps will stay consistent around 350-400. However, sometimes, if I have the air open even a little too much things start to get a little out of control and the flue probe will be pegged at the max (which I believe is 800-900) until I close the air down even more and the flue probe will go back to reading 350-400. It was during one of these times it was maxed out that this happened. This is maxed out with the damper completely closed

I checked the gasket as mentioned on a previous thread and it seems fine. If i shut the air off, the flames go right out and I pretty much create a backdraft when I open the door.

 

[Dug8498]

If the flue temps are excessively hot something is not right. Is there a key damper on the stove pipe? Here is another wild guess. Creosote flakes have dropped down to the bottom of the tee (at the thimble) and collected. Excessively hot flue gases are causing them to smolder and eventually ignite.

Yup, key damper on the stove pipe

 

[begreen]

It sounds like there is strong draft so for sure use that key damper and close it sooner. (probe thermometers are only for double-wall pipe). 900º surface is extremely hot.

It could be that each "bang" is shaking down more creosote flakes. With a cold stove, I'd pull the stove pipe and vacuum out the tee with a shop vac. And get the liner inspected and cleaned asap.

 

[Dug8498]

It sounds like there is strong draft so for sure use that key damper and close it sooner. (probe thermometers are only for double-wall pipe). 900º surface is extremely hot.

It could be that each "bang" is shaking down more creosote flakes. With a cold stove, I'd pull the stove pipe and vacuum out the tee with a shop vac. And get the liner inspected and cleaned asap.

Yeah I think I do have a very strong draft on my setup. Ok I will do. Thank you


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[Ludlow]

You have had 900 surface temps?

Maybe you said before, but how high is your chimney overall?

 

[Dug8498]

You have had 900 surface temps?

Maybe you said before, but how high is your chimney overall?

Yessir indeed. My thermometer maxes out at 900 so it could be hotter than that?

Not ideal I know and it’s happening less now that I’m getting the knack of this setup.

A little over 25 feet tall


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[begreen]

Yessir indeed. My thermometer maxes out at 900 so it could be hotter than that?

Not ideal I know and it’s happening less now that I’m getting the knack of this setup.

A little over 25 feet tall

You need to be closing down the air much sooner. Don't let it get over 500 and shut down the stove pipe damper sooner too.

 

[Dug8498]

You need to be closing down the air much sooner. Don't let it get over 500 and shut down the stove pipe damper sooner too.

Sounds good. I thought that I was doing that and the last time i checked on the stove all the numbers looked good. However, I had just reloaded the stove before I walked away, so maybe that had something to do with it.

I will start shutting everything down even sooner. Thank you

 

[bholler]

So we bought this house in January. The previous owner was required as part of the sale to have a sweep come out and inspect everything. The sweep found that the liner was "warped due to chimney fire". They installed a brand new stainless steel 6" liner in late November (the sale took another few months to complete). I unfortunately don't know if it was cleaned before it was installed as I wasn't there for that. I hope so!

Alright, I was hoping to not have to wait for the sweep to come as that may be another week; all sweeps are booked up right now. Thanks!

What type of chimney is this running through?