Amazing creosote build up. What is wrong?

[treefrog25]

Hi,

Every year I clean my chimney 1 or 2 times. I never get more than 1gallon of ash and black stuff.

This season I cleaned the chimney after 2 months of operation and got 5 gallons of black flaky creosote! That would have made a big chimney fire. Actually, a chimny fire started (which I put out before it got going) and this alerted me to the problem.

So, what am I doing wrong? I have been burning wood for years, same stove, same house but this year we are burning a little cooler that before and I also fixed a lot of leaks on the stove doors/glass etc. Why the sudden accumulation of creosote?

The wood is dry, hardwood. It has been stacked for 2 years.

The stove is a VC Defiant Encore with a catalytic converter. I have a digital thermometer and I run the stove at 1200-1400 degrees measured 2 inches from the exit of the cat. I assume if these temperatures are reached, the cat is working.

The probe thermometer on the flue reads 350 when in Catalytic mode.

I have read that some people make a roaring fire once a week before going to catalytic mode . I dont do this an maybe I should. Also, can I assume that my catalytic convertor is fully functional and is burning the creosote...maybe its not working anymore...but it reaches 1400-1700 if I push it.

Thanks for advice and comments.

Tim

 

[Chettt]

You got me on this one. Was your stacked wood covered well? I know many areas had a rainy summer. Other than that it doesn't make sense. Even if you had an old non-EPA stove I wouldn't think you'd have that much creosote.

 

[karri0n]

I don't know much about cats, but I'm quite impressed with that 1400 degree mark. If it's lighting off that hot, I wouldn't think you could be making much creosote at all.


Experts, please?

 

[Peter B.]

Definitely a puzzler... those temps would certainly suggest a very clean burn.

For the halbut, tell us about your chimney... could there possibly be a crack or break that's (now) admitting cold air and condensing (more of) the remaining creosote in your exhaust?

Peter B.

-----

 

[treefrog25]

My firewood has always been stacked in the sun, on 2 layers of pallets but not covered.
I just checked a few sample pieces pulled from the stack and using my lumber moisture meter,
the reading is between 12% and 20% moisture depending on which piece I check.
I normally get a wheelbarrow full and put it in the garage so there may be further drying
pior to burning. But I can tell you that there is never any hissing like when burning wet
wood.

 

[hh3f]

I think you should cover your wood sometime in September for the duration of the burning season. Sounds like there is more moisture in that wood than that meter is telling you. Also sounds like you should install a Stainless liner.My brother in law had a similar set up with no liner. He went from a 8 inch pipe to a approx. 12 inch square chimney that was on the side of the house. he also was using very seasoned wood. I could not believe the amount of build-up he had at the end of the season.

 

[BrotherBart]

Not saying it is what is happening but that happened to me with my old stove. After burning pretty clean for many years one year it started smoking and put a ton of creosote in the chimney. I finally discovered that it had popped a weld in the back right next to the flue collar and cold air was getting sucked in and mixing with the exhaust on the way out. It was cooling the exhaust which then glued itself to my chimney lining. I know cast iron stoves don't have welds, but just saying that an air leak can do that.

 

[LLigetfa]

The temps near the top of the flue also have to do with how much volume you let go up the chimney. If you slow the volume, you slow the speed and at the slower speed more of the heat escapes through the sides of the chimney on its slower rise, lowering the temps.

If a hot water tap far from the heater has a slow drip, the water dripping will always be cool.

 

[JerseyWreckDiver]

First question. Have you cleaned your catalytic combustor media? It should be cleaned once for approx. every cord you burn. Check it for damage also, burning too hot can damage it. If it has never been replaced, it may be time.

I also had a surprise this year about two months into the season. Lots of creosote and very, very wet... then it dawned on me, we use an old vaporizer to humidify the air and my wife this year moved it to the other side of the house, close to the stove! Lots of moisture being drawn in through air intake. Moved the vaporizer, problem gone.

I have a document, 3 page .pdf, on care & feeding of catalytic combustors. It's too large to post but I can e-mail it to you if you like.

 

[Peter B.]

treefrog:

If, as you say, you are suddenly getting (roughly) five times the amount of creosote that you've had in previous years, then the obvious thing to conclude is that *something has changed*.

It would probably be worth your while to inspect every inch of your stove and chimney externally... and as much of your stove internally as you can.

It strikes me that there may very well be an air leak somewhere between your catalyst and the sky... causing cooling and creosote condensation.

By the way, wood need not be wet or underseasoned to produce creosote... and you will still generate some creosote from firestarts.

Just more 'fuel for the fire'.

Peter B.

-----

 

[TMonter]

Is the cat on the stove clean and not clogged? Also how old is the catalyst? The cat may be working but not getting 100% of the combustibles leaving the stove which could cause the problem.

 

[jmichigan]

This is our 2nd month burning with our non cat stove. Last night we noticed a lot of smoke coming out of our stove when we opened the door & trouble keeping the fire lively and hot. Kept watching it and the smoke smell kept getting stronger. We took a flash light and shined it on the flue pipe and smoke was coming out of the seams!! HOLY CRAP!! We took all the logs out of the fire and out into the snow bank as fast as we could Then today went up to inspect the chimney outside and the raincap screen was completely plugged shut with creosote! We certainly didn't expect this or for creosote to form this fast. We are still experimenting with our stove and the temps and figure that we had two or three days of 40 to 50 degree temps where we burned the fire too cool for too long. We have good seasoned dry wood that my husband even goes to the extreme of removing all the bark off it to make sure it dries completely. Also think we probably contributed by closing everything down and burning it slow everyday while we go to work. My husband is also questioning if we may have our chimney too high causing things to cool too much at the cap where it was clogged. Chimney height is about 3 foot above the peak of the roof. Any thoughts or suggestions that we might be missing?

Jill from Michigan
Vermont Dutchwest cast iron non cat

 

[Jfk4th]

First question. Have you cleaned your catalytic combustor media? It should be cleaned once for approx. every cord you burn. Check it for damage also, burning too hot can damage it. If it has never been replaced, it may be time.

I also had a surprise this year about two months into the season. Lots of creosote and very, very wet... then it dawned on me, we use an old vaporizer to humidify the air and my wife this year moved it to the other side of the house, close to the stove! Lots of moisture being drawn in through air intake. Moved the vaporizer, problem gone.

I have a document, 3 page .pdf, on care & feeding of catalytic combustors. It's too large to post but I can e-mail it to you if you like.

How close to the stove was the vaporizer and were your temps very low with the stove while this was happening? I wouldn't think this would affect the stove unless you could see the mist stream being sucked in by the stove. I have a small Germ Guardian in my Florida room, about 7 feet away, the TV is between the stove and the humidifier. I haven't noticed anything with the stove but more comfort in the room and not getting shocked every time I touch the stove

 

[SteveT]

This is our 2nd month burning with our non cat stove. Last night we noticed a lot of smoke coming out of our stove when we opened the door & trouble keeping the fire lively and hot. Kept watching it and the smoke smell kept getting stronger. We took a flash light and shined it on the flue pipe and smoke was coming out of the seams!! HOLY CRAP!! We took all the logs out of the fire and out into the snow bank as fast as we could Then today went up to inspect the chimney outside and the raincap screen was completely plugged shut with creosote! We certainly didn't expect this or for creosote to form this fast. We are still experimenting with our stove and the temps and figure that we had two or three days of 40 to 50 degree temps where we burned the fire too cool for too long. We have good seasoned dry wood that my husband even goes to the extreme of removing all the bark off it to make sure it dries completely. Also think we probably contributed by closing everything down and burning it slow everyday while we go to work. My husband is also questioning if we may have our chimney too high causing things to cool too much at the cap where it was clogged. Chimney height is about 3 foot above the peak of the roof. Any thoughts or suggestions that we might be missing?

Jill from Michigan
Vermont Dutchwest cast iron non cat

Internal or external chimney? If external you'll probably want to insulate the flue pipe.

 

[TMonter]

This is our 2nd month burning with our non cat stove. Last night we noticed a lot of smoke coming out of our stove when we opened the door & trouble keeping the fire lively and hot. Kept watching it and the smoke smell kept getting stronger. We took a flash light and shined it on the flue pipe and smoke was coming out of the seams!! HOLY CRAP!! We took all the logs out of the fire and out into the snow bank as fast as we could Then today went up to inspect the chimney outside and the raincap screen was completely plugged shut with creosote! We certainly didn’t expect this or for creosote to form this fast. We are still experimenting with our stove and the temps and figure that we had two or three days of 40 to 50 degree temps where we burned the fire too cool for too long. We have good seasoned dry wood that my husband even goes to the extreme of removing all the bark off it to make sure it dries completely. Also think we probably contributed by closing everything down and burning it slow everyday while we go to work. My husband is also questioning if we may have our chimney too high causing things to cool too much at the cap where it was clogged. Chimney height is about 3 foot above the peak of the roof. Any thoughts or suggestions that we might be missing?

Was the pipe plugged with creosote or just the cap?

Can you remove the screen from the cap? I have this exact problem with my cap and removing the screen will help a lot. My main stove the screen is integral to the cap so I just make a habit of cleaning off the cap every 45 days or so before it plugs. The chimney doesn't gunk up but the cap always does.

 

[jmichigan]

We have about a 5 ft straight pipe single wall to the ceiling, triple wall through the ceiling, attic and outside.

Jill

 

[jmichigan]

This is our 2nd month burning with our non cat stove. Last night we noticed a lot of smoke coming out of our stove when we opened the door & trouble keeping the fire lively and hot. Kept watching it and the smoke smell kept getting stronger. We took a flash light and shined it on the flue pipe and smoke was coming out of the seams!! HOLY CRAP!! We took all the logs out of the fire and out into the snow bank as fast as we could Then today went up to inspect the chimney outside and the raincap screen was completely plugged shut with creosote! We certainly didn’t expect this or for creosote to form this fast. We are still experimenting with our stove and the temps and figure that we had two or three days of 40 to 50 degree temps where we burned the fire too cool for too long. We have good seasoned dry wood that my husband even goes to the extreme of removing all the bark off it to make sure it dries completely. Also think we probably contributed by closing everything down and burning it slow everyday while we go to work. My husband is also questioning if we may have our chimney too high causing things to cool too much at the cap where it was clogged. Chimney height is about 3 foot above the peak of the roof. Any thoughts or suggestions that we might be missing?

Was the pipe plugged with creosote or just the cap?

Can you remove the screen from the cap? I have this exact problem with my cap and removing the screen will help a lot. Main main stove the screen is integral to the cap so I just make a habit of cleaning off the cap every 45 days or so before it plugs. The chimney doesn't gunk up but the cap always does.

This seems to be the problem that we have also. Pipes had very little creosote but the screen was completely plugged shut. I think we are probably going to have to do the same thing that you do because our screen doesn't come off unless the cap comes with it.

 

[stoveguy2esw]

This is our 2nd month burning with our non cat stove. Last night we noticed a lot of smoke coming out of our stove when we opened the door & trouble keeping the fire lively and hot. Kept watching it and the smoke smell kept getting stronger. We took a flash light and shined it on the flue pipe and smoke was coming out of the seams!! HOLY CRAP!!
Jill from Michigan
Vermont Dutchwest cast iron non cat

if smoke can come out of the seams when the cap is plugged, then cooler air can and will enter through those same seams which lowers stack temps rapidly and will in many cases cause rapid creosote buildup. make sure you have good tight seals on the pipe seams to prevent cool air intrusion

to our origional poster, BB is right , i expect you have a flue leak , the cat is providing plenty of heat to help maintain the draft however the leakage is causing rapid cooling somewhere in your flue system, possible a seam may have been dislodged during a cleaning or somthing and is now allowing the cool air in.

if a masonary chimney , check the cleanout door closely , most are not gasketed and if they arent shut super tight you will pull cool air through them , especially in newer airtight stoves. this can result in not only rapid creosote buildup , but poor draft can happen as well if the leakage is signifigant enough.

 

[JerseyWreckDiver]

First question. Have you cleaned your catalytic combustor media? It should be cleaned once for approx. every cord you burn. Check it for damage also, burning too hot can damage it. If it has never been replaced, it may be time.

I also had a surprise this year about two months into the season. Lots of creosote and very, very wet... then it dawned on me, we use an old vaporizer to humidify the air and my wife this year moved it to the other side of the house, close to the stove! Lots of moisture being drawn in through air intake. Moved the vaporizer, problem gone.

I have a document, 3 page .pdf, on care & feeding of catalytic combustors. It's too large to post but I can e-mail it to you if you like.

How close to the stove was the vaporizer and were your temps very low with the stove while this was happening? I wouldn't think this would affect the stove unless you could see the mist stream being sucked in by the stove. I have a small Germ Guardian in my Florida room, about 7 feet away, the TV is between the stove and the humidifier. I haven't noticed anything with the stove but more comfort in the room and not getting shocked every time I touch the stove

Due to the layout and traffic between us, a five year old, two cats and a 120 Rotweiller, not to mention electrical access, she put it just a few feet from the stove on the air intake side with nothing in between. The stove also gets downfired a little more than I like as it is oversized for this house so temps are not always ideal unless outside is in the low 20's or less. The vaporizer is one of the old fashioned kind, it pumps out a lot of moisture, too much if the electrodes aren't cleaned often. I just moved it back to where it was originally, about 15 feet away from the stove and everything is fine again.

 

[treefrog25]

You guys have given me lots to think about.
The air leak suggestions sounds like a good place to start.

My set up is like this:
woodstove sits on the hearth of a firplace
8"round tee flue goes out the back of the stove and connects to
oval SS pipe which goes up 5' to meet
11x11" clay tile liner of external chimney.

At the junction of the oval SS flue and the 11x11 clay liner I have packed the corners with fiberglass insulation. This doubtless should have been done with some other material like ceramic wool or mortar. Well anyway, I noticed a small gap where the ss flue and the ceramic liner get real close. For sure this is letting air in there, so I'll work on getting that sealed up.

I plan to buy the 25' of 8" round ss and go all the way to the top which should solve the problem but it will be a bear to get the oval and round to join...so next spring.

Other cracks may be at the ss fitting joints and these I will fill with furnace cement. Other than that, I cant think of anything else that has changed.

Tim

 

[JerseyWreckDiver]

So what about the catalytic combustor? Have you cleaned/maintained it? I would look there long before worrying about air leaks...

 

[BrotherBart]

So what about the catalytic combustor? Have you cleaned/maintained it? I would look there long before worrying about air leaks...

If that cat is kicking 1400 it ain't the problem.

 

[treefrog25]

In the past, I have cleaned the catalytic converter with the vinegar/water solution. But its been a few years since I have done that. I do keep it clear of fly ash and vacuum out all the air passages at least 2x/year. My thought was that if I can get the 1400-1600 temp out of it then it must be working. But, since the catalytic unit is supposed to burn the creosote out of the smoke and it *appears* to be working, then how can there be a creosote build up. It was mentioned the smoke is never fully *cleaned* by the cat.

I'll work on the air gaps first and go from there to looking at the cat. I hate to replace it until its really not working anymore.

-Tim

 

[bmwbj]

In the past, I have cleaned the catalytic converter with the vinegar/water solution. But its been a few years since I have done that. I do keep it clear of fly ash and vacuum out all the air passages at least 2x/year. My thought was that if I can get the 1400-1600 temp out of it then it must be working. But, since the catalytic unit is supposed to burn the creosote out of the smoke and it *appears* to be working, then how can there be a creosote build up. It was mentioned the smoke is never fully *cleaned* by the cat.

I'll work on the air gaps first and go from there to looking at the cat. I hate to replace it until its really not working anymore.

-Tim

Treefrog, I too see my cat. temps always between 1400 and 1800 when my wood is burning properly, I also
see no smoke at all when it is at these temps, just the sweet smell of the cat. working.
I usually burn 10 to 15% moisture wood (mainly maple, but some red oak), but my set up is a 25' run straight
up with double wall stainless, and I am very lucky to only see about 2 cups of "dust" after a year of burning night and weekends. I would say your cat. is working perfectly, and would also say your exhaust must be cooling down
to much before exiting. You mentioned that your "screen" is completely clogged. I do not have a screen on my cap, this may be the reasons for my cleaner burning operation. I have heard that some people remove the screens altogether to have better results. My cap design never had a screen, and my certified sweep said it was not needed for my inspection.

 

[JerseyWreckDiver]

I'll digress on the cat issue as I don't have a cat. stove so it is not my area of expertise.

Unlike the chorus of "wet wood... wet wood" I know you can get creosote burning the driest wood ever known to man if the combustion is incomplete, since thats exactly what creosote is anyway, unburned combustion gases. So a few more things to throw out there; Has anything with your combustion air supply changed? Have you replaced all your all leaky windows with new ones??? Made the house more air tight in any way that might be restricting combustion air, Maybe added one of those XJ500 super turbo range hoods that is negatively pressurizing the house?