Huge increase in creosote after installing new Jotul

[K-du]

Last year I bought a new Jotul 400 wood stove. I burned 2 cords, the same as every other year with my old 1970's Jotul. I love the new stove, however to my surprise, when I went up on the roof to clean the chimney this year the 8.75" x 8.75" flue has so much creosote in it that it is reduced to a 5" round flue as far down as I can see with a flashlight. It's hard as a rock. My usual 8" brush is useless.

When I use the stove I keep it at the high end (temperature) of Jutul's recommendation for this stove.

I have two questions:

1) why is this happening?

2) how can I clean my chimney?

Thanks for any help.

 

[pma1123]

How dry is the wood you are burning?
Describe your chimney setup.

 

[xman23]

So all the same chimney, same well seasoned wood. All you did is change the stove? My guess is the chimney 9"x9" being to big, cooling off. Does the Jotel ask for a 6" chimney? The old stove must have had a hotter exhaust to keep it clean.
With that much stuff in there, luckily you didn't have a chimney fire.

 

[bholler]

I agree we need more info on the setup and fuel being used. As far as how to clean. In a situation like that i start wit ha small brush and work my way up if that does not work i get out the rotary cleaner with cables then rotary with chains. And a last resort is chemicals

 

[billb3]

I have two questions:

1) why is this happening?
Most likely a cold chimney with condensation occurring in the chimney. I've seen almost completely blocked about a foot above a thimble on a concrete block clay lined outside wall chimney. Not all the way up though.

2) how can I clean my chimney?

Carefully ? The above chimney had 2 clay liner sections broken from getting cleaning tools stuck and the chimney had to be replaced. I would have rpelaced with a SS in an enclosed chase, they put a block chimney back up again. From what I understand the same thing happened again and they now are on their third concrete block chimney but they put an addition on that end of the house so are burning the Jotul 600 a bit hotter.

 

[bholler]

Carefully ? The above chimney had 2 clay liner sections broken from getting cleaning tools stuck and the chimney had to be replaced. I would have rpelaced with a SS in an enclosed chase, they put a block chimney back up again. From what I understand the same thing happened again and they now are on their third concrete block chimney but they put an addition on the house so are burning the Jotul 600 a bit hotter.

Why would you not just reline the block chimney with stainless?

 

[K-du]

Thanks for the replies.

The wood is all oak, maple, birch, ash. I don't check moisture content. When I buy it in the Spring it has been on the ground in tree length since the previous fall (6-8 months). Prior to delivery, it is cut & split. I stack it under cover and try to allow as much air circulation as possible. When winter comes I start with last years left overs. I usually get into this years wood by thanksgiving. When I do burn it, it burns very well.

The chimney passes through the first 2 floors and then through the unconditioned attic and then out.

The chimney is masonry,

 

[billb3]

Why would you not just reline the block chimney with stainless?

Because an in-law replaced the whole chimney dirt cheap ?

 

[bholler]

Because an in-law replaced the whole chimney dirt cheap ?

yeah but you still have and uninsulated block lined chimney

 

[K-du]

CORRECTION> the stove is a F3 CB. It calls for a 6" flue.

 

[Wisneaky]

Step one. Make sure your wood is dry. I doubt if it is dry enough only being split in the spring.

Step two. Have a chimney sweep come out and try to clean it.

Step three. Reline your chimney with 6 inch liner.

Step four. Burn dry wood. Make sure its dry. Triple check. Dry only.

 

[K-du]

I have a friend that burns this exact same wood. He uses a moisture meter. By fall it has hit the sweet spot and is ready.

A liner costs nearly as much as the stove did. If I had known I'd need to line it, I would have kept my old stove. Funny how the Jotul dealer didn't care what size the flue is. Really funny.

Yeah, I'm definitely calling the sweep.

 

[bholler]

Funny how the Jotul dealer didn't care what size the flue is. Really funny.

That is why we started selling stoves. Many stove shops only want to sell the stove and are not concerned with it after that. Did they install it?

I have a friend that burns this exact same wood. He uses a moisture meter. By fall it has hit the sweet spot and is ready.

What is the sweet spot? How is it tested and is your wood stacked the same in the same orientation to the wind ect? There are many variables in wood drying so just because it gets dry at his place the way he stacks it doesn't mean it is dry at yours.

 

[K-du]

No They didn't install it.

Yes, you are correct. I understand your point about seasoning the wood etc.

The sweet spot is whatever the state wood burners assoc. says it should be. My friend is a very meticulous engineer and will not burn wood until it is ready. I don't know what the actual moisture reading is that he's relying on. But you are right. I shouldn't compare apples to oranges.

 

[bholler]

No They didn't install it.

Who did?

 

[K-du]

I installed it. In my ignorance, I thought I could just plug it into the old flue. I didn't realize that the flue can be too big. The stove performed great all winter.



I checked the manual for my previous stove. It had a 5" stove pipe and called for a 6" flue. It worked great for 35 years on the 9" flue.

 

[jharkin]

Agree with others... Wood is wet. You first EPA stove is a wake-up call on wood quality. The old stove burned hotter and send more heat up the flue letting you get away with sub par wood.


Green oak is nearly 40% water. You want that down to 20% for a modern stove. That can take 2 to 3 years after splitting.

 

[firefighterjake]

Most likely candidate (as mentioned) is the wood . . . modern woodstoves really need well seasoned wood. I burned some wood that was split a few months prior and thought I did well . . . in year two however with wood that was split a year previously I saw the proverbial light and realized just how great my woodstove would burn.

Another possible explanation may be in how you run the woodstove . . . assuming you know to reduce the air once the stove is up to temp . . . this has the counter-intuitive effect of creating a more intense fire (secondary burn), longer burn and cleaner burn vs. leaving the air control open.

 

[laynes69]

Have you ever checked the chimney while burning to see it it's burning clean? The new stoves don't burn the same as older stoves. It's still possible to burn them dirty if not doing things correctly. If it's glaze, that chimney just ain't staying hot, and anything that isn't burned in the firebox will accumulate in the chimney. An oversized chimney can cause sluggish draft, which will greatly affect performance.

 

[TheRambler]

Its either one of or a combo of, wet wood and too cool of a flue. You really need to split a few pieces and check those fresh faces with a moisture neter. If your splitting in the spring and burning that fall/wibtet you can almost certainly count on your wood being a large part of the problem. You can season pine and other softwoods pretty well in 6-10 months, but most hardwoods take at least 12-18 months, some 2-3 years. It doesn't really start drying until its split and stacked.

If you install an insulated liner you will probably see a great improvement.

 

[billb3]

yeah but you still have and uninsulated block lined chimney

Yup, cold and hard to get fires going with a cold stove too. Even being 25 feet tall.

 

[JA600L]

Here is a question,
Over the course of the winter, was the stove run 24/7 or frequently cold started?

Could you describe how you bring the stove up to temperature after a reload? Also, how do you adjust the air control and what burn times are you getting?

 

[jatoxico]

I installed it. In my ignorance, I thought I could just plug it into the old flue. I didn't realize that the flue can be too big. The stove performed great all winter.



I checked the manual for my previous stove. It had a 5" stove pipe and called for a 6" flue. It worked great for 35 years on the 9" flue.

If you have the stove plumbed into the old chimney which is almost 9"x9" you're going to struggle. The wood's probably not dry enough either but may be one time where it's not the biggest problem. You'll most likely have to bite the bullet and get the right liner installed. Good news is you may use less wood than you were before once things are running properly.

 

[peakbagger]

IMHO all this chimney discussion is off track. Creosote forms from incomplete combustion of the wood. Incomplete combustion is generally related to a poor stove design, operation or wet wood. Tree length wood loses little or no moisture from when its cut and one season is not enough seasoning time. There should be no secondary combustion in the chimney( at least we all hope so), so as long as there is adequate draft to run the stove (the OP didn't comment that the stove didn't run well) then the only thing the stack Is doing is carrying the incomplete combustion products and lots of water vapor then dumping it in the air. If the flue is sized correctly and is insulated, the incomplete combustion products and water vapor that could form creosote don't cool down enough and make it out the stack. Of course this means that 1/3 of the heat in the wood is also going up the stack. Keep the fire burning hot which means dry wood (no water along for the ride that sucks up a lot of energy going from liquid to water vapor) and far fewer incomplete combustion byproducts that form creosote.

My opinion is it could be a combination of how the OP runs the new stove and the wood which is too wet. The Jotul most likely has a lower exit flue gas temperature than the old stove, which is why this has become an issue. Before swapping out the chimney which may or may not solve the issue, find a real dry wood supply (worse case is buy bio bricks to mix in with the poorly seasoned wood). Now review stove operation, in theory the amount of heat output is controlled by adding wood, not by closing down the air damper. If the goal is long slow overnight burns, the normal method of banking it up with wood before going to bed and then cranking down the air damper is going to form lots of poorly formed gases and the Jotul's higher efficiency and lower flue temp is going to rapidly build up creosote. whereas the old stove may not have as it was probably less air tight and possibly a larger capacity which lead to hotter exhaust gas temp. The major initial change to stoves when the EPA stepped in was to add a set of secondary air ports hidden somewhere on the stove so that even if the air damper is closed, air still is getting to the firebox. The stove owner complains they cant get the overnight burns as well but the stove puts out less pollution. (Some folks think they are smart and plug these air ports so that they can crank down the stove)

I have a Jotul 606 sitting in the basement, its was one of the most efficient non gasifer Jotuls built. Its a 602 with an additional exhaust gas heat exchanger section so the flue gas leaving is quite cool They only imported them for one or two years as people in the US were burning their houses down with them as they were major creosote producers when run with wet wood and run improperly. They were incredibly popular in Europe and were sold for years without any issues. The differences were the Europeans were using dry wood and they weren't banking them up at night and then cranking down the air shutter. They run the stove by adding wood as needed keeping the air shutters partially open and either getting up in the middle of the night to add wood or just let it go out and relight it in the AM.

Feel free to spend lot of money on the chimney, but running truly dry wood (at least 2 seasons old) and alter the stove habits or replace the Jotul with an inefficient smoke dragon that hides the fact that 1/3 or more of the heat is going up the chimney.

 

[Huntindog1]

Did you let the stove heat up and get secondary flames started then slowly in 1/4 ways increments turn down the input air so as not to kill your secondaries. When you left the house and had the stove set to its all day burn setting did you still have secondaries flaming up in the top of the stove?

If your wood was green enough to put that much creosote in your chimney then I dont think your start ups were very easy. It would have taken you a while to see secondary flames going.

To help starts ups even on hot coals use kindling and a fire starter like a super cedar to get the heat built up in the stove fast and the kindling and supercedar will burn with the door shut where as the larger pieces of wood will not urn as easily with the door shut providing less air. Having the door shut and getting the input air turned down more quickly with out killing your flames will all help to get the heat built up in the stove more quickly. As having the door open or the input air wide open as you havent used kindling or firestarter , the increased air flow thru the stove flushes the heat up the flue.

Lastly my stove has a 6" exhaust size and it goes to an even larger masonry flue 7" x 11" . I found I couldnt run my stove running 6" pipe to my larger flue with an 8" thimble. It was just to hard to warm that flue from a 6" diameter pipe. What did work was I put the adapter right on top of my stove so I could run 8" pipe starting at the top of the stove all the way to my masonry flue. Which is like 5 to 6 foot run with an elbow. It worked as I think what helped was I had a larger volume of heated air feeding the larger masonry flue. As the dynamics of flue draw can be complex. Kind of kind like trying to suck from a really thin straw compared to a larger diameter straw. All I know is it worked as I switched back to double check and sure enough my problems returned.

Your best bet if you have the money is an insulated liner down your masonry flue.