Creosote questions with a Lopi Leyden

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milliburner

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Oct 6, 2011
34
Magic City, Northern Maine
I have been burning wood all my life, but don't recall seeing creosote form the way this stove is doing it. I took my pipe apart to move the stove. We did away with the hearth pad and built a hearth right into the corner. Anyway, the creosote is worse about 4 feet above the stove than it is at the top of the chimney, where the temps should be the coolest. We have had a warm november here and the stove hasnt been as hot as it probably should be and my wood isn't as seasoned as I would like. The stuff that is about 4 feet up is real dark and brittle flaky creosote. This is still in the single wall pipe. Once it passes into the metalbestos a little further up from that it was just a real light soot that came right out with the first pass of the brush. The other stuff took a little working back and forth.

I try to make sure to get the pipe up to 500 twice a day to keep the creosote down. Can anyone tell me why this is forming this way? I'm just curious.

Thanks
 
I'd consider sealing your single wall pipe joints w/ furnace cement. I was amazed at how much air gets sucked into those. When I switched to my new stove and new chimney, I could actually hear air getting sucked in there from time to time. It would suck the flame from a lighter into the joint.

I sealed them up w/ furnace cement on the advice of those around here a few weeks ago. While I didn't have much flaky creosote in my single wall, I definitely had more accumulation here than anywhere else in the system and was surprised as you are.

I'm looking forward to the mid season cleaning to compare.

pen
 
Hmm, I will try that and see what happens. Another question, is one wood more likely to create creosote than another. I know what answer is coming... WET wood. haha
 
You got it. Just don't ask what % moisture is dry vs seasoned unless you are prepared for the chitstorm that will follow!

Sounds like you know to keep the stove up to good temps on a regular basis as it is. If your wood weren't dry, you'd have problems with that (as you know).

pen
 
Also, I was surprised at how fast my cement started setting up. I'd recommend doing the cleanup as fast as you can. I used a ton of wet paper towels and it seemed to work. Not sure if a different solvent would work better or not, but that's what I had quick access to. I used a plastic bondo blade to apply it. Next time I think I'll try globbing a bunch in a ziplock bag and cutting the corner out and using it like a pastry or masonry bag.

pen
 
Thats a good idea, the ziploc dispenser. Yeah, I have read alot of the moisture content and seasoned wood pages. When the wife decides in late July that the pellet stove is out and we are going to wood there is only so much I can do. A lot of good Harley days were spent gathering wood. I'll be able to get ahead of it next year. By then she will want another pellet stove :smirk:
 
You'll want very dry wood to burn in the Leyden. There's a lot of info. on this site about running these downdraft type stoves.
Dry wood
Good Draft
Hot stove
Big Coal Bed
Just ask if you need specifics. Sounds like you'll be burning some small, hot fires if you're wood is not seasoned like it should be. And yes, with "wet" wood a downdraft stove can be a creosote factory. Good that you're cleaning the pipe.
 
milliburner said:
... the creosote is worse about 4 feet above the stove than it is at the top of the chimney, where the temps should be the coolest. We have had a warm november here and the stove hasnt been as hot as it probably should be...

...The stuff that is about 4 feet up is real dark and brittle flaky creosote. This is still in the single wall pipe. Once it passes into the metalbestos a little further up from that it was just a real light soot...

... I try to make sure to get the pipe up to 500 twice a day to keep the creosote down.
Click to expand...

The question is why does creosote form at all? The answer is low combustion temps leading to low flue temps. If creosote is forming way down low in the flue it is because that is the first point that the flue wall temps are below the condensation temperature of its components. Creosote is a rad mixture of numerous products of partial combustion (AKA smoke) mixed with water. You can never eliminate the water because your wood itself makes enormous quantities of it during complete combustion, even if the wood had 0% MC to start. But you can have an influence on if and where it condenses.

You need to run it hotter is all. Hard to do when it's warmer than normal outside. Try small, hot fires instead of filling and up and trying to control the heat output with air. Running the pipe up to 500º twice a day (how long BTW) won't help if you are running it at 200º the rest of the time. The black, flaky stuff you are seeing is the result of those 500º runs drying it out, but it ain't burning it away. Actually burning it away is, by definition, a chimney fire.

I'd try the suggestion of sealing the single-wall with cement. I wouldn't think that would make much difference, but these newer stoves can be pretty resistant to air flow, so maybe a strong draft can suck air in through the seams of the pipe. It's a cheap thing to do and may help, but I still think you will have less buildup once you start running that thing hot come January.
 
milliburner said:
I have been burning wood all my life, but don't recall seeing creosote form the way this stove is doing it. I took my pipe apart to move the stove. We did away with the hearth pad and built a hearth right into the corner. Anyway, the creosote is worse about 4 feet above the stove than it is at the top of the chimney, where the temps should be the coolest. We have had a warm november here and the stove hasnt been as hot as it probably should be and my wood isn't as seasoned as I would like. The stuff that is about 4 feet up is real dark and brittle flaky creosote. This is still in the single wall pipe. Once it passes into the metalbestos a little further up from that it was just a real light soot that came right out with the first pass of the brush. The other stuff took a little working back and forth.

I try to make sure to get the pipe up to 500 twice a day to keep the creosote down. Can anyone tell me why this is forming this way? I'm just curious.

Thanks
Click to expand...

Burning wood all your life then you know the big answer to creosote problems and that is burning wood before it is ready to be burned. You've also asked of one type of wood will cause more creosote than another. Well, yes and no. Most likely, oak will be worse than others but not because it is oak. It is because oak, although being one of the very best woods to burn is also the worst to dry. It gives up its moisture very reluctantly. That is why we won't try to burn oak until it has dried for 3 years after it has been split and stacked out in the wind to dry. Other woods will dry faster than oaks and ash is one of the best and will dry relatively quick.

On the furnace cement in the joints, that is how we have always done it and also 3 screws in the joints. Cleaning up is a breeze with wet paper towels. As for applying, you might even try what my wife does; just use the fingers. Looks terrible but that is how she likes to do it and who am I to complain if she wants to put that stuff on?! lol
 
I tried going around the pipe joints with a lighter and it would pull the flame in. I will be cementing the joints. Just guessing, but by pulling air there, I must be loosing some draft through the stove? It seems to draft good anyway but I would think the draft will be better with those joints sealed up.
 
Yes, most definitely. You will like the outcome of this short and easy fix.
 
Battenkiller said:
The question is why does creosote form at all? The answer is low combustion temps leading to low flue temps. If creosote is forming way down low in the flue it is because that is the first point that the flue wall temps are below the condensation temperature of its components. Creosote is a rad mixture of numerous products of partial combustion (AKA smoke) mixed with water. You can never eliminate the water because your wood itself makes enormous quantities of it during complete combustion, even if the wood had 0% MC to start. But you can have an influence on if and where it condenses.

You need to run it hotter is all. Hard to do when it's warmer than normal outside. Try small, hot fires instead of filling and up and trying to control the heat output with air. Running the pipe up to 500º twice a day (how long BTW) won't help if you are running it at 200º the rest of the time. The black, flaky stuff you are seeing is the result of those 500º runs drying it out, but it ain't burning it away. Actually burning it away is, by definition, a chimney fire.

I'd try the suggestion of sealing the single-wall with cement. I wouldn't think that would make much difference, but these newer stoves can be pretty resistant to air flow, so maybe a strong draft can suck air in through the seams of the pipe. It's a cheap thing to do and may help, but I still think you will have less buildup once you start running that thing hot come January.
Click to expand...

If he was burning too cool all of the time, wouldn't the "gunk" get even worse as he goes higher and higher up the flue?

Even if he runs the thing at max temps this will still happen if the joints leak enough.

After cementing my pipe joints I routinely see 75 to 100 degree higher probe temps. ~ 50 degree higher external pipe temps.

I had the same thing happen and I do NOT run my stove cool!

Never had this happen w/ the old 8in single wall. But the insulated / lined 6 in apparently draws harder.

pen
 
Troutchaser said:
You'll want very dry wood to burn in the Leyden. There's a lot of info. on this site about running these downdraft type stoves.
Dry wood
Good Draft
Hot stove
Big Coal Bed
Just ask if you need specifics. Sounds like you'll be burning some small, hot fires if you're wood is not seasoned like it should be. And yes, with "wet" wood a downdraft stove can be a creosote factory. Good that you're cleaning the pipe.
Click to expand...

I think this is the key to your problems. In a downdraft stove, if you are not getting good secondary combustion with a deep coal bed you are sure to have creosote problems.
When you burn, do you see any smoke coming from your chimney? Other than startups, you should be burning mostly smoke-free.
 
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