Creosote Buildup - Issues/remedies?

[BrokenToys]

Hello,
The previous weekend it was "get up and let's clean out the chimneys for this year" time and for reference there are 3 parties involved.

1. chimney 'A' = 8" clay flue with concrete block. upright wood stove-airtight
2. chimney 'B' = 8" clay flue with concrete block. uprigtht wood stove-airtight
3. chimney(s) 'C' = 8" and 12" back side by side (8" clay flue for wood stove-airtight with 4' of pipe at right angles to meet clay flue in wall, 12" clay flue for opposing room's fireplace).

Chimney 'A' (my chimney) - minor creosote buildup (about 1/2 a spackle bucket worth, no large chunks mostly small dusty pieces. Burn well seasoned (12-18 mos) hardwoods. 8" pipe meeting clay pipe in wall about 3' total pipe to meet the chimney.

Chimney 'B' - hardly any creosote whatsoever. 6" pipe to meet 8" adapter to wall where clay flue join is - again about 3' as well to meet chimney flue). Burns Pine, Hardwoods at about 50/50 ratio if anything more pine than hardwoods. Seasoned about 12 months or less.

Chimney 'C' - plugged SOLID [wish I took a picture honestly:it was like lavarock] with creosote, took a pool cleaning skimmer pole with a spackle knife and than a horseshoe stake- all in all about 3 hours to finally unblock. large (4-6" chunks) along with about 2 garbage cans worth of crap in it.

The entertaining part is that chimney 'C' owner (my uncle) swears up and down pine is no good and is "$^*#" to burn to chimney 'B' (other uncle - older brother of uncle #1) - and I'm just the nephew young enough to go up and ladder and clean them while they throw their logic at each other.

Back on topic - I still can not for the life of me figure out why his one chimney builds up so much creosote. Could it be that the adjoining chimney on chimney 'C' causes the exhaust remnants to solidify faster and cool down and build up? All 3 chimneys were built around the same time (late 70's) and just wondering how to remedy this if it is even possible? I don't feel like cleaning chimneys out every 2 months with snow on rooves/etc. After seeing the chimney of the one that burns pine too suprised me-i would have expected something but it really really clean.

If anyone would have a clue you alls here should. I apologize for the rambling post; but any and all replies will be read. Thanks !!

 

[CrappieKeith]

so...I'd like to help figure out the puzzle but there are way too many ?'s needing answers.
Make up air
Flue rise
#'s of 90s
to start.....
I'll let some others chime in 1st.

 

[chopperfreak2k1]

i'm no authority on the subject but i would guess that 8" chimney "c" is being cooled too much by 12" chimney "c" and the reulst is a high level of build up.

 

[CWME]

My thoughts are with chopperfreak but have no idea. Could just be the way the guy is running the stove. Interested in what the experts we have here will say. I have an external block chimney that has 6" flues running side by side and could potentially experience the same issue.

 

[dave_dj1]

It could be "how" the owner of chimney c is not burning his stove up to it's potential. I have seen people try to get extremely long burn times out of their fancy airtight stove, the fire NEEDS air to burn, plain and simple. Choke out the air going in and flue temps will not be enough to prevent creosote build up. Tell him to open up the stove once in a while!

 

[BrokenToys]

After extensive trick-o-treating...here is what i can add:

CrappieKeith - The chimney with the problems has starting from the stove (it's a horizontal stove with a rear exit horizontal sleeve-no baffling chambers) it meets a 90 degree turn, goes up vertically roughly 46" with a damper about halfway up that pipe, than meets another 90 degree angle than continues horizontally approx 36" to enter the clay duct in the brick wall to meet the chimney flue which is about 12" long before going upwards and out the chimney - approximately 18 feet up to the top. there is also a cap (square with a 12" high screen and a little roof)
I am thinking now due to the amount of angles and how the stove is burned long and not excessively hot (as dave_dj1 and chopperfreak2k1 also mentioned) it may be a combination of these all plus going up a pipe that never really gets a full heat potential and also suffers rapid cooling before exiting. Also I would say that the fireplace is maybe used about 20% of the time as compared to the wood stove. All 3 of us pretty much burn our wood stoves non-stop unless the ashes have to be emptied.

Possible thing to do:
take infared thermometer and measure pipe temperatures at each angle when at full burn. if there is a drastic difference maybe remove one of the 90's and go with different bends and/or move stove closer to the wall? I can see how shorter pipe leading to the chimney could fix it maybe?
Granted for as accurate as it can be-my stove pipe exiting my wood burner is pretty much at it's best heat production/longevity at about 450-500 degrees which i use my magnetic thermometer to regulate (i placed it under where my damper is). The Uncle that burns the pine/hardwoods and spotless chimney is about the same as well. I know his stove and mine only have about 36" of single wall seamless vertical pipe (both our stoves are vertical top feeders and top exhaust pipe) before meeting the 90 degree bend to go to the exit flue in the chimney.


That or maybe just the clay flue is on it's way out due to slower burns and is subject to faster cresote buildup? While scrubbing with the brush [i did about 30 passes up and down the full length of the pipe once the blockage was out] i didn't see any kind of structural damage to the clay or any kind of brittleness to the clay nor during cleanout was there any broken chips of flue pipe in the soot/creosote. I am leaning towards slow low temp burns though the more i think about it. I may have to try to convince my uncle (lol) that removing the bends and shortening the pipes will help..or just burn some pine like his brother does :taped: !!

Thanks for the replies too - !!

 

[borat]

From my experience, burning properly cured pine, spruce, balsam, tamarack will not create any more creosote than any other wood. I burn mostly conifer wood and my chimney's never need cleaning. Properly cured wood and the occasional hot burn will go a long way to keeping a chimney clean. Tell uncle "C" to start burning some conifer wood and crank the heat up at least once a day.

 

[Sandhill Crane]

Where we used to live I put an 8" single wall pipe in the tile chimney because creosote was seeping out the joints in the attic. The only buildup after that was from the roof line up, especially the screening on the cap.
Where we are now, we have double wall pipe from the framing, the wall in one instance and ceiling in the other, all the way to the cap. I cleaned them yesterday and got a double handful of dust out of each, not the popcorn chunks we used to get in the top three feet at the other place. The worst being the caps themselves.
I burn a Vermont Castings top load catalytic converter, with outside air intake, and dry two year old oak. We have a temp gauge on the pipe one foot above the stove and burn about 400-500 degrees, often with the windows cracked open. We also do not burn 24/7, but close, so we do restart often, in the evenings and burn through the night, reload in the morning before leaving.
Fuel type, temperature of burn, external cooling of flue pipe, out side air source (good draw), and regular cleaning are all factors.

If there is the slightest concern I would seek out a professional. My neighbor is a volunteer firefighter. He said 40% of their winter calls are chimney fires or house fires that began in chimneys. Check your smoke alarm batteries!

 

[Encore]

Could it be that he's turning down the flue damper?

 

[lampmfg]

Get a Kuuma and forget about the creosote altogether...

 

[CrappieKeith]

Get a Kuuma and forget about the creosote altogether...

is that all you got????
C'mon your a furnace company...let's see some viable solutions to this guys dilemma.


It's most likely a drafting issue. Too much horizontal pipe...too many 90's too large in diameter and it's brick so it's a cold flue...A liner would help.
Of course if it is idling all day that would also be a no no...
Chances are that if the flue is cold and over sized and not enough rise it wouldn't matter what appliance you put on it except for the Magic Kuuma.