Help with rapid creosote buildup

[Adm3745]

Hey everyone. We have a new jotul f45 hooked up to an exterior masonry chimney via 6" single wall pipe.

We've been burning from Dec 1-Feb 8 24 hours a day for about 5 days at a time. Gone through about a cord. All oak not ideal around 22%.

I took apart the stove pipe today and was shocked to see so much creosote so close to the stove. It almost looks like creosote is building up in the stove itself. I try to burn hot (stove top at 600) all day then we pack it full at 11:00 pm shut it down and wake up to a solid coal bed at 8 everyorning.

Looking for any insight on this. Is this an excessive level of creosote?

Why is it so close to the stove (I measure occasionally with infrared and get 400 or so 12" up the stove pipe )

What could I do differently. Could the overnight burns be the cause of this? The winter here has been mild. Can't imagine what this would look like after 2 cords.

 

[begreen]

It's good you are checking. This is a lot of build-up for one cord. Some of the wood may be higher than 22%. Oak splits take a long time to dry internally. Do some of the splits bubble and sizzle on the ends as they heat up? How is the moisture being tested?

What is more important is what the chimney flue looks like. The flue gases will cool down rapidly in an exterior chimney. Is the stove venting into an insulated 6", insulated stainless liner or into masonry tiles in the chimney? If tiles, what is their ID?

Get the chimney cleaned asap.

 

[Adm3745]

I tested 5 pieces. Ranged from 16 to this one which was the highest at 24. I do see sizzling, bubbling ends on about 1/5 logs that I put in.

The 6" stove pipe feeds into a 2 ft x 8" horizontal clay thimble which is shown as covered in the picture and then turns up 25 ft into a square 8" masonry chimney.

I realize my wood is not perfect yet , but is that the primary root cause here or should I be looking at an insulated liner?

Knowing I routinely spot check the vertical stove pipe at 400 degrees I fully expected there to be zero creosote in the stove pipe but expected some in the vertical chimney section because of the cold walls. The creosote levels went down after the horizontal run and get less and less up the chimney. It's bizarre.

Could the flu size increase slow and cool down the gases enough in that short two foot space that that is why I'm seeing all the buildup?

 

[begreen]

I tested 5 pieces. Ranged from 16 to this one which was the highest at 24. I do see sizzling, bubbling ends on about 1/5 logs that I put in.

The 6" stove pipe feeds into a 2 ft x 8" horizontal clay thimble which is shown as covered in the picture and then turns up 25 ft into a square 8" masonry chimney.

I realize my wood is not perfect yet , but is that the primary root cause here or should I be looking at an insulated liner?

Knowing I routinely spot check the vertical stove pipe at 400 degrees I fully expected there to be zero creosote in the stove pipe but expected some in the vertical chimney section because of the cold walls. The creosote levels went down after the horizontal run and get less and less up the chimney. It's bizarre.

Could the flu size increase slow and cool down the gases enough in that short two foot space that that is why I'm seeing all the buildup?

View attachment 309550

That's the wrong way to test. Internally this wood could be 30-40% moisture content. The wood needs to be resplit and then tested in the middle of the freshly exposed face of the wood.

 

[begreen]

The added moisture is really cooling down the flue gases. After they hit the cold exterior chimney they will cool down a lot more. The oversized flue is further slowing down the flue gases. Get the chimney cleaned asap. The upper part of the chimney where the flue gases are coldest may have heavy creosote accumulation. That can be a chimney fire waiting to happen.

 

[Adm3745]

Well that's a huge difference. Lesson learned #1.

Will properly seasoned wood mitigate that buildup in a big way, or can the chimney setup still be a contributing factor.

 

[kennyp2339]

Will properly seasoned wood mitigate that buildup in a big way, or can the chimney setup still be a contributing factor.

It will help in a big way.. you can still have build up in the chimney, but not as bad as fast.

 

[begreen]

A cold exterior chimney will still cool down the flue gases rapidly, but once it is completely warmed up it may be ok. Have the sweep do a thorough inspection to make sure the chimney is safe.
Dry, fully seasoned wood will lead to warmer flue temperatures which will definitely help mitigate the problem. If you don't have next season's wood already stacked and drying, it's time. Some wood speicies dries faster than others. Wood doesn't start drying until it's been split and stacked off the ground. Oak, hickory generally take 2-3 yrs to dry after being split and stacked. See if you can get some ash wood.

5 tips to drying firewood

The art of firewood isn't cut and dry. Here's how to make your wood dry thoroughly to burn well. Words: Nadene Hall 1. Cut your firewood in spring or early summer so it gets at least 6-9 months to dry out; if you cut it in autumn or winter, it won’t be dry enough to use until the following year...

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The Wood Shed forum here has lots of talk on processing firewood. Look up homemade kilns there for accelerating the drying. https://www.hearth.com/talk/forums/the-wood-shed.17/

 

[kborndale]

If you are buying wood then buy next year's supply tomorrow. All wood dealers will tell you their wood is seasoned and ready to burn but it's extremely rare that you can buy wood that is ready to burn. Expect any wood you buy to need a year at a minimum to be dry enough to burn. And on a side note, wait until you burn some dry wood and see how much more heat it gives off than wet wood.

 

[Adm3745]

If you are buying wood then buy next year's supply tomorrow. All wood dealers will tell you their wood is seasoned and ready to burn but it's extremely rare that you can buy wood that is ready to burn. Expect any wood you buy to need a year at a minimum to be dry enough to burn. And on a side note, wait until you burn some dry wood and see how much more heat it gives off than wet wood.

That's where I got burned. We just bought the house I bought a cord local and thought it was good. Have a couple cords cut and stacked so far for next year. Hoping the oak is ready for next winter. Already down to 24% after 2 months. Not sure if that's good progress or not.

 

[peakbagger]

IMHO, overnight burns and mild winter are contributing causes. Modern stoves are designed to run in a much lower range of operation that older stoves, overnight burns usually means getting the stove nice and hot then loading it with wood and cranking down on whatever air control there is to carry over the night. Far better off letting run hot and then letting it run out of wood and relighting it in the AM.

 

[Wildflush]

As others mentioned oak takes awhile to season. If oak is split small with good sun, wind and top covered maybe 1.5 years but good 5” to 6” splits figure 2 years minimum 3 best. Next year bring a piece of oak in your house for a few days then resplit and take the reading in the middle of the spit parallel to the grain. That will give you a good read. Your pic looks like you are closer to the end. I bet it is wetter in the middle. The name of the game is to get ahead. I like to have 4 cords in rotation.

 

[Wildflush]

IMHO, overnight burns and mild winter are contributing causes. Modern stoves are designed to run in a much lower range of operation that older stoves, overnight burns usually means getting the stove nice and hot then loading it with wood and cranking down on whatever air control there is to carry over the night. Far better off letting run hot and then letting it run out of wood and relighting it in the AM.

That’s exactly what we do with our Vista. Since I have a small fire box so won’t get overnight burns we get the house temp to about 76-77 and won’t reload before bed. House is insulated well so carries up through to the morning.

 

[Wildflush]

OP another thing you can do is get some Redstone wood bricks at Tractor Supply. I have used these to supplement my cord wood and they are excellent! Run long and hot and mix with my hardwood.

 

[Woodsplitter67]

That's where I got burned. We just bought the house I bought a cord local and thought it was good. Have a couple cords cut and stacked so far for next year. Hoping the oak is ready for next winter. Already down to 24% after 2 months. Not sure if that's good progress or not.

Just as an FYI the majority of the wood that you will purchase from the firewood sellers will not be seasoned property. It will be seasoned some. It is rare the get truly seasoned wood and if it is seasoned well.. it will cost you.

Your better off doing the following. A.. purchasing green wood its cheaper and well your going to have to let it season anyway. B.. Purchase log lenth and cut and process it yourself. this has alot of advantages, like cutting to the lenth of firewood best for your stove, being able to split the the desired thickness. I split all 3 small, medium, large. You also can split square and rectangle for your overnight burns to pack the box and get the longest burn times possible.

If you have the space Id definitely go the woodshed route. Split and stack it in there. No babysitting with tarps or wood getting wet and slowing the process of drying. You haven't gotten alot of snow this year.. Try getting to a tarped stack with 3ft of snow on it.. that kinda sucks..

 

[peakbagger]

Although a woodshed is hard to beat, there are short term alternatives that can go in quick and relatively cheap. The trick is the use the pile to support the roof by using scrap wood screwed into the firewood with long deck screws. I keep an eye out for potential roofing materials and horde them until I build a stack. I have wood splitter and make flat splits out of the large logs and use them to stack up the corners but many folks drive vertical posts on the ends. Run a rope from one end to the other when you are stacking and the posts are not going bend out of vertical. The trick is to get a overhang on all sides and make sure there is an air gap at the top. When wood dries the moisture tends to go up and if there is not an air gap at the top of the pile it tends to condense under the top cover and then dripping back down into the wood. Some winters I get 3 to 4 feet of snow and never has a top cover fail. With low pitch and smooth roof the snow tends to self clear. If I am really worried, I just support the top supports from the stack with a couple of splits.

I screw the roofing to the top supports, no issues with wind and I live in high wind zone.

 

[Wildflush]

Wood sheds are great but cost money. I double up my commercial tarps covering just the top of the stack with para cord tied to masonry bricks. Works great. Since they are single stacks getting snow off with a small shovel and brush is not a problem. My dad did this for over 40 years and worked great. Never a problem getting his wood seasoned. I would have to build a big wood shed for my 4 cords not to mention the distance from the house which is a big negative. Also wood shed should be near sun and wind not always an option for positioning. Always trade offs just do what works for you.