Clogging SS chimney

[CVPeg]

Newly returning to wood burning. Been doing it daily now since October, and am having issues with my chimney becoming easily clogged. Apologize for the length of this, but trying to provide as much info ahead of time. Wondering about the root of my problem - is it placement of the house/chimneys? Or is it wood seasoning, the chimney(s), anything else?


This is a two story house. with a gambrel roof, 2 wood stoves (1 on each floor), and 2 SS chimneys. This house was formerly a ski/bike shop w/ an upstairs apartment. Place originally built about 1989, original owners lost it to the bank, it sat vacant for a year or two, we purchased it from the bank.

When we first had this house, we did limited burning in the downstairs wood stove - a Shenandoah. The upstairs is a Vermont Castings Intrepid. During those early years we had a big pile of wood delivered, and all of it too big to burn in the Intrepid.

I am in upstate NY. The house is located at the bottom of the eastern slope of a very high hill. This locale known for being windy, but the house is fairly protected by the hill.

The Shenendoah is on the gable end of the first floor, with a very high SS chimney running well past the top.

The Intrepid is in the center of the 2nd floor, with its SS chimney running straight up through the peak of the roof.

The house is very solid - quite airtight.

Due to various reasons - allergies, divorce, moving away for school, work - I stopped using the wood stoves. However, I had the chimneys checked/cleaned a few years ago. Then again at the end of this past summer. They were almost pristine. The chimney sweep had put chimney caps over the tops of both SS chimneys a few years ago. This year he also installed a damper in the flue of the Shenandoah. The stove had always burned hot and fast, and after reading suggestions on here, and from friends, thought this would help slow it down a little. Also last year, the bottom extension of the Shenandoah's chimney fell off. It ran below the elbow - I guess to allow for easy clean-out/and some accumulation. A local welder/family friend, put a cover back on the opening, but not a new extension.

Had about a face cord of wood cut last year at my neighbors - cut small enough for the Intrepid. Had to buy the rest of my wood from others. Several various individuals. Tried to buy only seasoned. The majority of what I purchased (about 4 cords) was seasoned, but had some odd pieces in it including a lot of small round logs. The wood mostly ash and maple. Bought another face cord of 8 month old ash. And my hunters on my land just cut up about 2 cord of downed trees (fallen 1 & 2 years ago) - oak, maple, ash, even some elm. The latter wood understandably, has been hardly used. (And this past month started logging my land, so now have about 15 cord newly cut/split in a huge pile in my back yard for next year!)

When I started this year, I tried out both stoves. The Shenandoah is not easy, the Intrepid impossible to start. The draft was terrible for the Intrepid. When we purchased this house, the roof - which covers more than half of the front of this house, was very stained below that chimney - almost 1/3 of the roof below it discolored. I had the roof replaced two years ago. Since I am downstairs 95% of the time, I've concentrated on the Shenandoah, and haven't bothered since to use the Intrepid. Have electric baseboard, so only burn when present. But returning to burning wood, a couple of new thermostats, and keeping them at 59 degrees has decreased my electric bill from $900 last December to $300 this December.

I understand all this wood burning has quite the learning curve. And yes, I wasn't burning hot enough. I start my fires with newspaper (not colored ads/inserts) and usually with a starter brick, with the smaller, older logs alongside. A few weeks ago I bought a moisture meter, and am now reading everything I put into that stove. The small round logs are not great at burning, even though they are seasoned. Nor does anything approaching 20% even if I throw it on a hot flame. But the Shenandoah can burn through in under an hour with decent wood. It keeps me busy!

About 3 weeks ago, I started getting some smoke coming more and more into the house when opening the door/starting the fire. Called the chimney sweep who is tied up with a large local commercial account. He advised doing a burn with a large amount of newspaper. Done. Worked ok for a day or two. Then got impossible. Called welder friend. He went out and bought a chimney brush and extensions and opened it up. It was a mess. With especially a large accumulation at about the roof edge He cleaned the length of it for me, and told me I should do it again in another 3 weeks. He also thought the chimney cap was not a great idea for this chimney. And noticed one or two tiny holes on the outside of the chimney close to the bottom. Said I may have to get it replaced in the near future, but it should be ok for now. :-( He also said the stainless steel chimneys had to have only very well seasoned wood??

Well, now 2 weeks later, it's already getting smokey when I open up that door again. I've hardly used the damper since, and kept the air input almost wide open the past week. Have tried to use only the best wood, but am running low on anything with almost no moisture.

Am about to head out after our new 10" of snow and attempt to do another cleaning.

I thought our chimney sweep was the cat's meow. But now not so sure about his advice. And wondering about the chimney caps.

And believe perhaps the location of this house isn't forgiving to keeping fires going easily. But having to clean the chimney every 2-3 weeks? Is that normal?!?

(PS At the beginning of the season, my hunter friends suggested I burn a chimney cleaning log about once a month, but then I read it doesn't do much past the elbow. True/false? Would it help?)

Thanks to all who stayed with me. Would love any advice. Also if down the road I should have the chimney replaced by local builders, or go to a stove specialist. Been really trying to be frugal. It's tough!

 

[DAKSY]

IMHO, your wood is too wet. That's the reason chimneys & liners get plugged.
Split ALL your wood, & burn your stoves HOT.
Even the smallest rounds will not "season" properly if they aren't split

 

[CVPeg]

Thanks, DAKSY - been trying to stay to the driest wood - why I now have the moisture meter, and bring wood in to burn a couple days ahead, which I've always done anyway. Read to make sure it's under 20%, but wood at that level hasn't done well. Been trying to stay at 14% or less.

Tried cleaning the chimney just now - the flimsy extensions only allowed me to push the brush up about 15 feet. My welder had sturdier ones. Called him about where to find them - they don't make them anymore, so he's going to make me one for the bottom. He's a good guy.

Called the chimney sweep. He's coming out tomorrow. Agrees the chimney cap could be a problem

Chimney sweep, who lives about an hour away, says it's unusual to have to be cleaned out more than 2x a year.
Welder, who lives nearby, says it's typical in our area to have to clean out chimneys every couple of weeks. Does any of that have to do with the wind we get?!? The heavy snow? My being at the foot of a mountain?

See why I need this forum? ;-)

 

[blades]

1 only check wood moisture level on a fresh split face exterior means nothing
2 wood can not be frozen, you will get false reading
3 If when you are up top or use binoculars if there is a screen / mesh type chimney cap installed at top of flue , remove the screen portion, all those screens do is plug up and very quickly to boot in real cold temps. they are more for keeping various small animals out then anything else. Can always be replaced in late spring.
4 Intreped- if flue is within 10 ft of someting higher ( like the roof) combined with being on the hill slope you likely are suffering from a downdraft problem.
5 Never figure any bought wood to be properly seasoned, always planned to stack it for use at least a year later.
6 some of the compressed wood logs or bricks combined with your less than good wood might help resolve some of your difficulties.
Sounds like a neat home other than that.. How about a few snap shots
7 Welcome to the forum.

 

[CVPeg]

Thanks, Blades - this is very helpful. And thanks for the welcome.

I've only tested the moisture on the splits from the old downed trees, but have hardly used any - maybe a half dozen at most all season.
Been using most of the "seasoned" wood I bought. That's what I regularly measure. I have a feeling the screen is the type to keep out animals - and hopefully will be down tomorrow when the chimney sweep shows up.
The flue on the Intrepid comes right out in the center of the peak. But considering all the staining on the roof from years prior to my ownership, I think it was an issue all along.

Here are photos. First two before the new roof put on. The Intrepid's chimney is in the center, Shenandoah's on the end. Third with the new roof. Last photo to give some idea of what a winter can be like here, and how surrounded the house is by the hill above, which goes much higher than the photo shows.

 

[Earth Stove]

Your SS on the outside will never draw right IMHO. The best flue location is right near the center like the other flue. Outside chimneys, prefab flues, steel pipe, etc. will not readily heat up quickly, ergo (good draw or draft quick).
I'd agree with the other replies that your wood is probably not dried out, cured enough. I would never put any kind of flue on the outside.
Burn smaller dry wood with hot fires until you figure out what the problem is with the center flue?
The central location of any flue has all of the inside dwelling thermal heat to quickly get good draft going. HTH

 

[bholler]

Is it an insulated chimney or a double wall air cooled chimney? If it is insulated it should heat up just fine and if you are burning right you should only need to clean once maybe twice a year. The screen could be the problem or sure. And if your sweep told you to clean your chimney by burning a load of paper you need a new sweep that is a very dangerous practice.

 

[Corey]

Some comments inline below

The Shenendoah is on the gable end of the first floor, with a very high SS chimney running well past the top.

While the exterior chimneys may not be great to start, once running, I don't think it should be a huge issue. Though to plug up a chimney in 3 weeks as you say, you would need to have a chronic problem for the entire time the stove is in operation. A little smoke at start-up won't plug a chimney that fast.

The house is very solid - quite airtight.

This could be a part of the issue. If the house is 'really' that tight, you might need some way to get outside air in for the stove to draft properly. This is especially important if you have anything else trying to draft out of the house as well... kitchen stove vent hood, bath fans, clothes dryer, second stove running (or even just it's flue open), etc. One way to check - (with a clean flue and the fire started) crack open a window in the stove room. If the fire suddenly springs to life, it's a sign you need fresh air into the house to allow the stove to exhaust out.

Also last year, the bottom extension of the Shenandoah's chimney fell off. It ran below the elbow - I guess to allow for easy clean-out/and some accumulation. A local welder/family friend, put a cover back on the opening, but not a new extension.

This could be another source of problems. If the cover is not installed completely air tight and the remaining chimney in good enough shape to seal 100%, you can draw air in at this joint which will kill the draft to the stove. It's especially concerning because parts of chimneys should not just 'fall off' - and in the rare case where something might - it should be easy to re-secure. The fact the old part was not replace indicates there might be corrosion or other damage making it unfit to re-use? This suggests there may be equivalent damage to the remaining pieces. Either way, the flue needs to be 100% air tight and completely sealed to the stove for proper draft.

The Shenandoah is not easy, the Intrepid impossible to start. The draft was terrible for the Intrepid.

Yet the Intrepid is the stove with the central / enclosed flue? So it should be the easier of the two stoves to start...it's slight drawback being on the second floor, so perhaps a bit shorter flue. Though overall this also suggests there is an issue with draft / fresh air in the house...possibly due to the 'airtight' issue above.

A few weeks ago I bought a moisture meter, and am now reading everything I put into that stove. The small round logs are not great at burning, even though they are seasoned. Nor does anything approaching 20% even if I throw it on a hot flame. But the Shenandoah can burn through in under an hour with decent wood. It keeps me busy!

This seems to be almost two contradicting statements...small/round/relatively dry wood doesn't burn, but when it does, it burns through in under an hour which suggest a really fast rate? As mentioned above, be sure to re-split the wood and take a moisture reading near the center. Ends can often read 'dry' even though the bulk of the log is still wet.

About 3 weeks ago, I started getting some smoke coming more and more into the house when opening the door/starting the fire. Called the chimney sweep who is tied up with a large local commercial account. He advised doing a burn with a large amount of newspaper.

I think I would fire the sweep and never have him back. That newspaper stunt is equivalent to saying, "Well, my pistol won't fire reliably" and the solution being "Load up a few rounds and look into the barrel while pulling the trigger...maybe you can spot the problem" I would say never...ever... burn a large amount of newspaper... ESPECIALLY if you think the flue might be plugged. In the best case, you send a bunch of fly ash up the flue which will get stuck in what ever goo is already in there and make the problem worse. If things don't go ideally, you have a huge ball of fire in the stove an no where for it to go except back into the room and In the worst case, what ever is plugging the flue does light off...then you have a raging flue fire which may or may not stay in the flue.

He also thought the chimney cap was not a great idea for this chimney. And noticed one or two tiny holes on the outside of the chimney close to the bottom. Said I may have to get it replaced in the near future, but it should be ok for now. :-( He also said the stainless steel chimneys had to have only very well seasoned wood??

Might have something here as well. If the cap was not 'meant' for that chimney, possibly the holes are too small, the way it's attached blocks some of the draft, or maybe it's even slipped down blocking some of the openings. Definitely worth a double check. The holes on the outside - again, seems weird...this is a stainless flue? What made holes in stainless? The key again would be to make sure they do not allow outside air into either the flue which would kill draft directly, or that they don't allow substantial air into any air gap/ insulation space in the flue. This could create a draft between the layers of the flue and help cool it excessively...which again hurts draft.

Well, now 2 weeks later, it's already getting smokey when I open up that door again. I've hardly used the damper since, and kept the air input almost wide open the past week. Have tried to use only the best wood, but am running low on anything with almost no moisture.

With air input wide open, I'd think you would almost have a run-away fire if the draft was good, so again suggesting some issue with the house being tight, plate/cap not fitting the flue, and or letting outside air in.

(PS At the beginning of the season, my hunter friends suggested I burn a chimney cleaning log about once a month, but then I read it doesn't do much past the elbow. True/false? Would it help?)

If it makes you feel better, fine, but the logs are generally regarded on here as a waste of money. No substitute for a good mechanical cleaning.

Thanks to all who stayed with me. Would love any advice. Also if down the road I should have the chimney replaced by local builders, or go to a stove specialist. Been really trying to be frugal. It's tough!

Good luck. Sounds like there are a few main issues to check out. Mainly, if the house is really 'airtight', if the chimney cap is correct and not blocking the flue, if the 'replacement plate' at the bottom is tight fitting and not allowing extra air in, and get a line on what ever is causing the corrosion and exactly how bad it is.

 

[930dreamer]

Some great points here, looking forward to what you find out.

 

[CVPeg]

Wow, Corey. Great information. Thanks so much!

Chimney sweep has come and gone today. Didn't want to take the cap off. His front wheel drive van couldn't make it up my driveway so he wouldn't bring the ladder up even though I offered to help. Cleaned the chimney again, and said he'd leave his rods and brushes here. But my welder friend is already making me sturdier rods. Sweep also didn't remember that he had installed the cap a few years ago. "All I'll have to do" is clean the chimney myself when needed for the rest of the winter. :-( And maybe he'll take the cap off in the spring, but thinks it may make the draft worse being wide open? He's also recommending getting my new brush trimmed to make cleaning easier? (Welder friend thinks that's poor advice - defeats the purpose...)

Think the sweep just didn't want to bother removing that cap on a cold day with a foot of snow on the ground... Understand safety wise, but he offered yesterday. He agrees the cap might be an impediment, but oh, well... :-(

Started a new fire after he left. To me, it still wasn't burning well early in the fire - with logs that are supposedly seasoned, relatively small, dry (under 14%) and split. Yes - I'm thinking the wood maybe still isn't seasoned as well as it could be. This is 10 month old Ash. But wood from this batch had burned well before... All wood seems to turn black before really catching in the beginning of the fire. Maybe this is an ignorant observation. But just seems that previously it didn't look like it was smoldering first, and then catching.

40 minutes later, the fire is finally really roaring. And needing more wood. It does use a lot.


I have a feeling the extension on the chimney that fell off was a big help for whatever this model is. I asked the sweep how the chimney is made. SS on the outside, insulated, then SS on the inside.

The reason the extension couldn't be put back on last year was because it had rusted out/corroded around where it joins, and had fallen off, laden with several inches of heavy thick junk. I hadn't used the stove for a few years before that happened.

Who knows how the hole on the outside of the chimney got there. It is visible from the ground - probably around a 1/3" - about 9 feet up from the ground. Sweep says it's only on the outside layer, though. Doesn't go through to the middle.

Corey, I did try opening the front door, and it did not seem to change how fast it burned.

Well, this sweep is not my knight in shining armor. He's a local fellow, well known, and used by big commercial accounts, fancy houses. But I agree his knowledge - not dissimilar to some others out here in the boonies. When I asked his recommendation about maximum moisture content of wood for stainless steel chimneys, he didn't have a clue. He said, well, you got to burn the wood you have here, right?

I just called a stove retailer for the name of someone who could do stainless steel chimney work, and was given the name of a new chimney sweep?

So think it boils down to I have a sensitive, older chimney, that I can only burn the best wood in. And/or the cap needs to be removed, and/or the extension put back on.

Thanks again for following the next chapter.

As an aside, I am now nervous about using the damper - worrying about increasing creosote. I'm leaving the damper open, and adjusting the fire down within the best temperature range for operation with the air intake. Agree? Do I dare use the damper at all?

 

[CVPeg]

Also, in response to the comments that the center chimney should draft better than the one on the gable end - the Intrepid on the 2nd floor in the middle is a very small stove. This Shenandoah at the end of the house on the first floor much larger. Does that change how a chimney might draft?

 

[bholler]

Well your wood should be between 15 and 20% on a freshly split face for any chimney. if there is a hole in the outside of the chimney it is time for a new chimney. That hole is letting water into the insulation and making that insulation useless. also if the bottom extension of your stainless chimney rusted off tat is a good indicator that you need a new chimney to. as far as the cap goes if you are burning correctly with good wood a cap even with a screen should not be a problem. you should normally be controlling th stove with the air intake only use the damper to slow the draft if it is pulling to much and you cant control the fire with the air control.

 

[CVPeg]

Thanks for the info, bholler. The air control works fine. Just had the damper added this year to try to slow down the burn, but I'd rather not use it if it increases any build-up of creosote.

 

[Corey]

I guess a couple other key questions - what is coming out of the flue during all these cleanings? Is it a dry/flaky material? globs of tar-like gunk, something else entirely?

I don't think this is a secondary burn stove, (correct me if I'm wrong) so should be a little more tolerant of wet wood. Do you ever see any hissing / foam at the log ends? That is a sure sign of wet wood. The fire may burn in a crackling / popping manner with dry wood, but if you hear a bunch of sizzling, hissing, etc, also a sign of wet wood.
If it is a secondary, then that brings up a whole new set of operating possibilities.

 

[Earth Stove]

Wow All good stuff mentioned here. So the "air tightness" could have a starving for air effect on all combustion devices????

 

[begreen]

True. Modern stoves are not air-tight in the sense that they always admit some air for more complete combustion.

 

[CVPeg]

So new chimney sweep stopped by yesterday, to give an opinion on the chimney, and will be writing up an estimate to possibly have it replaced in spring.
First thing he observed, the plate the welder fashioned to go across the bottom when the lower section fell off is not insulated - so right there would be an issue with it drawing properly. And agrees the hole further up means it's deteriorating within as moisture goes into the insulation.
He also thinks it's just a tad bit short. And that the cap isn't bad, but it's not really meant for this chimney, and yes - could be why it's closing up. If the chimney starts closing up again soon, I'm having this fellow out to remove the cap.
He also noted the height of the hill (mountain to some!) behind my house - another reason the chimneys would not draw well.
He believes the chimney would have had a lifetime warranty. Found out who installed it 25 years ago, but they have no paperwork of course, and neither do we having bought the house from the bank. But it should not be too much of a job to install the new one - since I'll just continue to use the outside chimney, and the brackets are attached well and can be used for another. So labor should be minimal.
He's also suggesting I look into a new stove. Turns out mine does not have a catalytic converter (not sure why I thought mine did...). And of course, the newer ones are so much more efficient. My Shenandoah is such a wood hog. They deal in Jotul and Harman. So guess I'll be thinking about that in the near future - if I keep this place. The idea of leaving the stove running, after all the work I've put into wood this year - is sounding very appealing!

Oh, and Corey - what has been coming out of the chimney has been dry/flaky material. But it has been just jammed in a couple of spots. worse at the roof line. When the bottom of the chimney fell off last year, it had about 8" of thick gooey solid matter in the bottom. But we hadn't used the stove/chimney for probably 8 years beforehand. I wouldn't be surprised if it was left from years before, and water just seeped in over time. It was rusted/corroded around the edges where it joined the rest of the chimney. When if fell and hit the ground, it was so heavy it made the house shake. I eventually took it to the dump and wouldn't be surprised if it weighed a good 20 pounds, packed into that narrow cylinder.

 

[Corey]

...

Oh, and Corey - what has been coming out of the chimney has been dry/flaky material. But it has been just jammed in a couple of spots. worse at the roof line. When the bottom of the chimney fell off last year, it had about 8" of thick gooey solid matter in the bottom. But we hadn't used the stove/chimney for probably 8 years beforehand. I wouldn't be surprised if it was left from years before, and water just seeped in over time. ..

The 'dry flaky' generally indicates you are burning the stove as well as can be expected. If you have 'wet / glossy / tar like' material, that can indicate a smoldering or oxygen starved fire. It sounds like what is happening - the insulation in the old chimney has deteriorated in a few spots which is letting the inner pipe get cold. When it's cold, the smoke condenses at those points and leads to the build-up you see. Of course, the pipe only has to plug at one point for the whole thing to stop working. Plus, the more it plugs, the slow the smoke travels and the cooler it is...both of which mean even more material can condense at the cold spots...so downward spiral.

No chimney cap + creosote/tar + water could easily lead to corrosion on the bottom section. Stainless steel is a weird animal...it actually needs oxygen to build up and/or repair it's protective coating. So a piece of stainless exposed directly to the atmosphere will stay in good condition for a long time. If you cut off that oxygen...say put the stainless steel in oxygen depleted water, or have a slurry of creosote/tar/water setting 'dead' in the bottom of the pipe, then it can start to corrode in short order. Sounds like that's what happened here.

Anyway, best luck getting it sorted out. Sounds like this new sweep is on top of things and will get you set up with a good system. Though feel free to post any of his proposals back on here. There are a lot of good folks which can point out possible issues and help steer around known issues which may develop.

 

[CVPeg]

Thanks, Corey. Your information is valuable and really interesting. Appreciate being able to understand what's happened.