Odd creosote ooze coming out of bottom of chimney

[BlueRidgeMark]

Hi, folks,

I have a Grandpa Bear Fisher with a top exit. I've been heating my home with it for about 12 years. It's oversized for our house, so we run it damped down. I burn dry hardwood seasoned (usually) 2 years, and mostly oak.

But still, with it closed down we do build up quite a bit of creosote. I deal with it by running a brush through it from time to time, and the occasional hotter fire.

About a week ago, I woke to the smell of burned wood in the house. I got up to check and found a blob of black stuff oozing out of the bottom of the chimney where it meets the stove. The stovepipe sits outside the collar of the stove. I'd say there was maybe a cup of this stuff running down across the stove. I cleaned it up thoroughly, and went to bed. In the morning there was just a tiny bit more that hadn't gotten very far.

We had had some rain, but I have a stainless steel cap on top that usually does a good job of keeping the rain out. In the past, my creosote buildup has always been dry, hard stuff on the inside of the pipe. I have never seen this wet ooze before in my life. It hasn't happened since either.

Any ideas? Why the liquid ooze, and why now? Have others seen this?

 

[Lloyd the redneck]

I have also had that. I attributed mine to condensing before exiting the chimney. Still not sure what it is tho

 

[peakbagger]

Since you have an oversized stove and burning "damped down" the wood doesnt burn fully and various consituents in the wood are driven off as gases up the stack. The gases cool and condense on the walls of the stack forming creosote. The creosote can be dissolved, it water can get in the stack it will run down the chimney. There is a thread on how to modify a Fisher stove with a secondary baffle, it can reduce the creosote somewhat but the only real option barring a new stove is do short small burns. Anytime you run a stove "damped down" you are putting a lot partial combustion byproducts up the stack and some of them like creosote will condense out. Essentially what a chimney fire is creosote condenses in the stack and slowly back in solid. Then you have a good hot fire and the creosote heat up enough that it starts to burn and once it starts burning it will heat up more creosote until it like a blowtorch.

 

[bholler]

What peat said but i would like to add that solid creosote can also melt and turn into liquid when heated to the right point. It can also do it in a chimney fire which can lead to a nasty burning ooze. Which is a very bad thing especially in a slammer or poorly done direct connect like lloyds. One thing is that your pipe should be run in such a way that anything running down the pipe is directed into the stove not out of the pipe. But honestly you need a smaller stove that you can durn properly

 

[BlueRidgeMark]

What peat said but i would like to add that solid creosote can also melt and turn into liquid when heated to the right point.

Hmmm. I've never seen that, but I'm 100% sure that's not what happened this time. It was a mild night and there was just a small fire going at the time. Just embers, really.

 

[FishKiller]

i'm not going to explain to you the process of a chimney fire... but i will tell you that your burning practices are poor at best. you said it was raining and you were running a small fire... when was the last time you cleaned out? have you burned hard since the clean out? i kinda suspect that you heated up some creosote enough to loosen it up, then the rain (wind conditions?) may have caused it to run back down as your clearly running a cold flue. you would need to post your clean out routine... pipes, flue, and when you did them... in order to get a better idea of what is going on.

 

[BlueRidgeMark]

I'm quite aware of the process of a chimney fire, thank you. There is no doubt there is creosote in there, the question is why it oozed out. It's normally in the form of hard flakes on the inside of the flue, and we've had much heavier rain, even recently, and we've never had liquid creosote oozing out.

 

[bholler]

I'm quite aware of the process of a chimney fire, thank you. There is no doubt there is creosote in there, the question is why it oozed out. It's normally in the form of hard flakes on the inside of the flue, and we've had much heavier rain, even recently, and we've never had liquid creosote oozing out.

It is either melted creosote or moisture condensing and carrying creosote out with it. Chang the pipe setup so it is directed back into the stove and it wont happen. Or better yet get a stove that is sized appropriately so you can fun it correctly and avoid the creosote to start with.

 

[BlueRidgeMark]

The stove was built to have the pipe sit outside the collar. I guess Bob Fisher didn't know better in those days. As for changing the stove.. well, there's no money for that, and it's worked quite well for me for the last 12 years or so, and the previous owner probably bought the stove new back in the 70s. Understanding how to use it and keeping the chimney clean means it works just fine, so it ain't broke. If it aint' broke, it doesn't need fixing.

I'm just wondering about the sudden appearance of oozing creosote, when for last 12 seasons it has not been seen. No change in the wood, burning habits, and we've seen far more rain without ever seeing oozing creosote.

 

[bholler]

The stove was built to have the pipe sit outside the collar. I guess Bob Fisher didn't know better in those days. As for changing the stove.. well, there's no money for that, and it's worked quite well for me for the last 12 years or so, and the previous owner probably bought the stove new back in the 70s. Understanding how to use it and keeping the chimney clean means it works just fine, so it ain't broke. If it aint' broke, it doesn't need fixing.

I'm just wondering about the sudden appearance of oozing creosote, when for last 12 seasons it has not been seen. No change in the wood, burning habits, and we've seen far more rain without ever seeing oozing creosote.

If you dont want to hear the answer why ask the question? There are adapters made to keep this from happening. And there are more appropiatly sized stoves avsilzble used for not much money at all.

 

[Lloyd the redneck]

If you dont want to hear the answer why ask the question? There are adapters made to keep this from happening. And there are more appropiatly sized stoves avsilzble used for not much money at all.

Go back in the woods get off the computer

 

[bholler]

Go back in the woods get off the computer

What exactly does that mean??? He asked a question it was answered by multiple people and he was given options to adress it.

And now he says nothing needs fixed it is working fine all but the creosote running out of the pipe onto the stove. It makes no sense

 

[BlueRidgeMark]

He asked a question it was answered by multiple people

Nobody has yet answered the question. I did NOT ask why creosote forms. I did not ask how to prevent it. I'm quite well aware of how it forms and how to prevent it.


The question is, "Why did this suddenly appear when it has not been seen for 12 years?"

The flue didn't suddenly jump outside of the collar. The rain has been much heavier in the past. The wood hasn't changed. The burning style hasn't changed.

Nothing has changed except on one occasion, I had oozing creosote, one time, whereas in the past it's always been very dry flakes on the inside of the chimney.

 

[blades]

atmospheric conditions and the perfect alignment of the stars? so there is creosote in the pipes, enough humidity and a small fire just enough to liquefy the creosote but not enough to dry it back out = black ooze. Indication that pipes need cleaning. Freight train sounds from the flue are not a good thing. Might want to check your insurance policy. Insurance companies are a bit finicky when it comes to wood burning appliances. just sayin.

 

[BlueRidgeMark]

so there is creosote in the pipes, enough humidity and a small fire just enough to liquefy the creosote but not enough to dry it back out = black ooze.

That sounds plausible.....

I have seen plenty of liquid creosote, as in this post, but I have never seen or heard of black ooze like this. Has anyone else seen this?

 

[bholler]

That sounds plausible.....

I have seen plenty of liquid creosote, as in this post, but I have never seen or heard of black ooze like this. Has anyone else seen this?

Yes as a sweep i see it all to often. We have one guy who has it rigged up so he can collect it out of his cleanout with 5 gal buckets. He refuses to take our advice and change his burning habits

 

[peakbagger]

I have seen it many times in a pulp mill, creosote can be formed by lignin in the wood and there is a byproduct of the pulping process that is burned for power called black liquor which is mostly lignin. Its solid at room temps so the pulp mill keeps it hot. When there is leak, it can spray out and form black icicles.

A local hospital in North Conway NH converted their heating system to heat the place with what is effectively liquid creosote. I think Bates College in Lewiston Maine recently switched over. If you want more info http://www.ensyn.com/heating-fuels.html

 

[Seasoned Oak]

But honestly you need a smaller stove that you can durn properly

One of the best reasons is the reduction in wood use, if you want to discount the fire hazard out of hand. When i realized how mush LESS wood i was burning in a new efficient wood stove i phased out my old stoves quickly . Less wood burning is not only less sawing ,cutting, stacking,splitting ,carrying ,and storing . But less fire hazard as well.

 

[mnowaczyk]

So “what’s different?”

Every log is different.

Maybe not the rainiest time you’ve ever burned, but maybe one of the only times you’ve burnt just coals and a cool fire that warms the creosote in the chimney, and there’s not only the condensation of all of the exhaust, but also the atmospheric condensation.

Maybe the wood is not as identical as you think.

Could you be using the wrong shaped chimney brushes, perhaps a round brush in a square flue and the corners have finally built up so much that it’s now oozing down?

Have you tried taking a little bit of that liquid creosote outside to see how much blow torch you need to put on it before it catches on fire?


Sent from my iPhone using Tapatalk

 

[coaly]

The stove was built to have the pipe sit outside the collar. I guess Bob Fisher didn't know better in those days. As for changing the stove.. well, there's no money for that, and it's worked quite well for me for the last 12 years or so, and the previous owner probably bought the stove new back in the 70s. Understanding how to use it and keeping the chimney clean means it works just fine, so it ain't broke. If it aint' broke, it doesn't need fixing.

I'm just wondering about the sudden appearance of oozing creosote, when for last 12 seasons it has not been seen. No change in the wood, burning habits, and we've seen far more rain without ever seeing oozing creosote.

No, all stoves when yours were built had pipe that was 6 or 8 inch OUTSIDE. What was needed to fit stove pipe didn't exist. It is designed to have pipe inserted INTO collar so any condensate drips back into stove to be consumed. (Page 2 in your Owners Manual) Common practice was to over-crimp the connector pipe smaller until it fit. Later, (1980) pipe was made with the INSIDE diameter to fit stove pipe.

You should have a 6 inch liner the way you burn your stove so you can keep it closer to 250*f. all the way to the top. Above that flue temp the water vapor will exit without causing excessive creosote, and certainly won't have condensate to run down. **You could have some leaks into your flue cooling the flue gasses below the condensing point that were never there before.**

Your stove was built with the oversize outlet for open door burning and for allowing more heat to escape into a larger chimney made for a fireplace. They work fine reduced to 6, but codes technically only allow one inch reduction. If you don't have an added baffle, that will reduce smoke and creosote formed by a huge amount. The baffle thread in the Fisher Forum details baffle specifics. It was written for the single door stoves but can be adapted to your double door very easily.

Sizing the stove to the area heated and chimney is very important. The trained people in sales at the Fisher Factory Showrooms were very good at making sure the right model and size went to the right customer. Many times a customer would buy larger expecting to add on, or felt they needed more heat than the correct model produced. Larger is worse than undersized. Many times you can sell your stove in the summer to someone who needs that model and pick up the correct stove for your application making money on the deal. Do you use it for open door burning to view the fire? That was the main reason for the design of your stove. The single door Bear Series has a larger cook top and is more efficient for your use and you would find they are easier to start (with less fuel) in a warmer climate than what you're used to.