Hi all, so I am planning on installing a new wood stove to vent up through a liner in an existing masonry chimney on an exterior wall. The main problem, however, is that the stove needs a 6" diameter liner, but the interior dimensions of the chimney are only 4.75" x 18.25". Doing the math tells me there's way more than enough volume so with my simple understanding of this concept I assume it should be possible to get the correctly shaped liner up this chimney and still have a good draft. Unfortunately I don't really know exactly what that looks like. Do I just go for some kind of oval liner, even though I understand those are fairly expensive? I had an idea of possibly using a fitting down by the stove that is essentially a Y that changes the 6" opening to 2 4" openings which is about the right volume, and then sort of having a "double-barrel" liner going up the chimney. Any idea if this has this been done and if it would cause problems with the draft? Complicating matters quite a bit even more so is the fact that as far as I can tell the existing chimney is unlined. Any help here?
How to fit a liner in a too small chimney
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2 liners will not work you will probably need a 7" liner ovalized to maintain the proper volume. But honestly going down to 4" wide you may need to go up to an 8" liner to have the proper volume. Is there any way you could put up a class a chimney instead?
jatoxico
Minister of Fire
I don't think your double barrel idea is a good. No way any manufacturers have ever tried such a setup and cleaning would be a nightmare. What do you mean unlined, no clay tile? How about some pics or a diagram?
Yeah unlined for sure i have never seen any clay tiles made that size. I have seen double liners tried before and usually only one of them pulls the other sucks air down. I guess it it was engeneerd correctly you may be able to get it to work but like you said cleaning would be a real pita
Yeah unlined for sure i have never seen any clay tiles made that size. I have seen double liners tried before and usually only one of them pulls the other sucks air down. I guess it it was engineered correctly you may be able to get it to work but like you said cleaning would be a real pita
jb6l6gc
Minister of Fire
You'd probably have a hard time ever getting anyone who would touch it or certify it. Plus if its not an approved method no stove manufacturer would ever warranty it.
Gotcha thanks guys. Maybe ovalizing a larger liner would be the way to go. Here are a few pics of the chimney from the top for reference. I have never worked with stainless steel liner before - is it difficult to ovalize without breaking? I'm assuming I need insulation as well, so I figure going down to 4" in the narrow axis might not even quite be sufficient.
![[Hearth.com] How to fit a liner in a too small chimney](https://www.hearth.com/talk/data/attachments/165/165503-02fc23735658cc640259ca59b7ea37ad.jpg?hash=2Wpp38Z7Jd "[Hearth.com] How to fit a liner in a too small chimney")
![[Hearth.com] How to fit a liner in a too small chimney](https://www.hearth.com/talk/data/attachments/165/165504-51cbda40c904115d2b1e17a1e497a7cc.jpg?hash=7iWOpYro12 "[Hearth.com] How to fit a liner in a too small chimney")
![[Hearth.com] How to fit a liner in a too small chimney](https://www.hearth.com/talk/data/attachments/165/165505-0855cc80d655a1b3345a4a6f36c3f6ad.jpg?hash=_1NaedjwVE "[Hearth.com] How to fit a liner in a too small chimney")
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jatoxico
Minister of Fire
To insert a liner with insulation which in this case appears to be mandatory I say no chance, go to plan B. I am curious what that is servicing.
jb6l6gc
Minister of Fire
Haha yes it is a crappy chimney, thanks guys. It was at some point servicing the very small fireplace pictured below. Bike pump for scale? The opening is about 25" tall. It is definitely a strange little chimney. But anyway, no chance? Just doing some math shows me you can get an ellipse the same area as a 6" diameter circle if it's about 3" x 12". Is that not possible to find such a product or ovalize liner down to those dimensions myself? That leaves almost an inch on either side of the narrow part to insulate. Is that not enough? Really no chance, or just a difficult job? Not having ever done this before, it seems like it could still be possible.
![[Hearth.com] How to fit a liner in a too small chimney](https://www.hearth.com/talk/data/attachments/165/165506-51b2d0bd4bde48b54d7762a5c93bf43a.jpg?hash=gnoWtVgAA- "[Hearth.com] How to fit a liner in a too small chimney")
There is no liner in the chimney and a metal liner will be tight. Lord knows how you would clean it.
jatoxico
Minister of Fire
Just to jump in, I don't think it's simply a matter of square inches but the configuration/shape affects draft. From what I know that's too much ovalization. By the time you ovalized an insulated liner that could pass down that chimney the sides would practically be touching. That's kind of a cool little fireplace BTW.
Thanks, yeah I wish I could use it haha. Yeah I wondered about how the shape might affect draft. Not being a physics major, I don't exactly know how it would. However, I would suspect that it's primarily the shape of the opening at the top few feet that would affect it the most. Meaning theoretically you could return the pipe to a circular shape and extend it above the chimney a couple feet or so to ensure you didn't mess with the physics of the draft too much. Do you suspect that the main oval part would still affect the draft negatively in that sort of configuration?
hoverwheel
Burning Hunk
If the new stove is going there, abandon the old fireplace "in place", build out the new hearth and install a new class A going straight up above the stove.
It's an interesting feature, but it doesn't look very practical.
It's an interesting feature, but it doesn't look very practical.
Is that a small coal fireplace?
My small understanding about the physics is that gasses like to "swirl" up the chimney, so I would guess extreme ovalizing would hurt draft. Rigid round flue would be the most ideal.
My small understanding about the physics is that gasses like to "swirl" up the chimney, so I would guess extreme ovalizing would hurt draft. Rigid round flue would be the most ideal.
Actually I'm not too sure about it being a coal fireplace. I don't know much about what a coal fireplace looks like compared to a wood fireplace. Any tips on how I could tell? Thanks for all the tips about not using that fireplace, all. I guess I have no choice but to start looking at whatever plan B is since from all the experts on here, not a single person said they would recommend trying to install a liner in that chimney.
jatoxico
Minister of Fire
Removal of that old chimney would probably go quick, up top anyway. Is any brick exposed on the side of the house or attic? If you have room, a nice free standing stove sitting on the old hearth but w/ new class A might be a lot easier than it looks at first. More pics!
Coal requires a lot of under-fire air, and the ones I've seen pictures of tend to be somewhat narrow... The lack of a "flue liner" seems like a possible clue to me as well because coal, at least the hard anthracite variety, doesn't form creosote, although I'm not sure if that was a traditional-thinking reason not to use a clay inner liner.
The fact that the "basket" holding the fuel goes all the way to the sides and back (and its shape too) seems like another clue to me.... that it was designed to hold a load of coal instead of a few logs. The design of the bottom of the basket would be the main clue though--is it open down there (so coal would just fall out) or closed in a grate?
edit: Although you're in Colorado, so that would be weird, I doubt hard coal was very popular (or available) out there...
edit2: Well how about that, Anthracite actually was mined in Colorado a long time ago. http://nepacrossroads.com/about23104.html "Anthracite was mined in Colorado (near Leadville IIRC) many years ago but no not now."
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Looks like a coal fire place to me. I would save yourself the hassle and abandon that chimney / tear it down. And go with class a pipe. Easier cleaning easier installation and probably less money.
I agree as well, coal fireplace. If you want something that will heat you are going to need to rip that fireplace/chimney out and start over again, that is just way to small in every way to be worth dealing with. I can honestly say I have not seen something like that chimney before.
Well, I guess you could go with a freestanding pellet stove in front of it, that liner would fit.
Well, I guess you could go with a freestanding pellet stove in front of it, that liner would fit.
yes it is a coal fireplace for sure We see allot of 4' wide interior chimneys servicing old coal fireplaces or other coal units. And no you generally cant get a liner in them. I think it is time to consider other options
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