Jotul C350 with a 5" liner

[riverfire]

I've finally built a roof platform, removed the crown and front damper plate with an angle grinder, and hauled out the 5 inch liner so I can measure the chimney dimensions. Here is a high level summary of chimney dimensions with additional detail and photos included below to help clarify.

Summary:
chimney height (fireplace floor to top of chimney): 15' 9"
upper chimney outer dimensions: 18x22.5"
upper chimney inner dimensions: 10x15.5"
lower chimney smoke shelf bottleneck: 6.5x15.5" (estimated)
smoke shelf height (from fireplace floor): 5'4"

After reading through more posts, I'm inclined to go with a Duravent rigid round pre-insulated 6" solution for the upper portion of the chimney, and either: (a) a short uninsulated flexible 6 inch; or (b) a short blanket/mesh insulated flexible oval 6" compatible (4.5"x7.4") to work around the smoke shelf. The smooth inner wall of the rigid sections is very appealing to me for regular cleaning and I like the idea of modular sections for a solo installation.

If I could remove the smoke ledge or a portion of the opposing bricks (5' 4" up) I could go with 6" pre-insulated round all the way up, but it seems like a fair amount of work and risk.

Another option to improve draft would be to extend the rigid round sections above the height of the chimney. I believe I read this in a post here, but I'm unsure of what kind of extension is advisable.

I wanted to update the post here before going ahead with it now that I'm able to get better measurements.

Details:

For the main upper portion of the chimney, the inner dimensions are roughly 10x15.5" all the way down to the smoke shelf.

Minor dimensions shown below:


The view from the top of the chimney to the fireplace floor is relatively unobstructed until the smoke shelf. The height from the top brick surface to the fireplace floor is 15' 9".



In the photo below you can just see the edges of a paper plate on the fireplace floor between the smoke shelf (lower portion of photo) and a thin cast iron piece remaining from the damper assembly in the back of the fireplace that is proping up some fire bricks. A portion of the masonry that was chiseled out just above the in the first installation can be seen in the same photo.



Below is a look up the chimney from the fireplace at the same bottleneck after I removed the front damper plate with an angle grinder. This view shows the bricks that were chiseled out from the initial installation, the same thin cast iron bar from the above photo supporting a few fire bricks, and the lower surface of what I believe is a smoke shelf looking up the chimney.




The height of edge of the innermost portion of the smoke shelf (red dot from range finder in photo below) is 5' 4" above the fireplace floor.




A height of 5 feet 4 inches matches the top bricks of the mantle in the fireplace.



I used a small plastic canoe paddle with a minimum width of 6" and maximum width of 6-5/8" to test the bottleneck. The 6 inch portion seems to pass through fine, but the 6-5/8" is just barely too wide to fit through straight.



The 6-5/8" section of the paddle catches on the narrow dimension of the chimney at the location of the smoke shelf, but there is plenty of room in the other dimension.

 

[bholler]

I've finally built a roof platform, removed the crown and front damper plate with an angle grinder, and hauled out the 5 inch liner so I can measure the chimney dimensions. Here is a high level summary of chimney dimensions with additional detail and photos included below to help clarify.

Summary:
chimney height (fireplace floor to top of chimney): 15' 9"
upper chimney outer dimensions: 18x22.5"
upper chimney inner dimensions: 10x15.5"
lower chimney smoke shelf bottleneck: 6.5x15.5" (estimated)
smoke shelf height (from fireplace floor): 5'4"

After reading through more posts, I'm inclined to go with a Duravent rigid round pre-insulated 6" solution for the upper portion of the chimney, and either: (a) a short uninsulated flexible 6 inch; or (b) a short blanket/mesh insulated flexible oval 6" compatible (4.5"x7.4") to work around the smoke shelf. The smooth inner wall of the rigid sections is very appealing to me for regular cleaning and I like the idea of modular sections for a solo installation.

If I could remove the smoke ledge or a portion of the opposing bricks (5' 4" up) I could go with 6" pre-insulated round all the way up, but it seems like a fair amount of work and risk.

Another option to improve draft would be to extend the rigid round sections above the height of the chimney. I believe I read this in a post here, but I'm unsure of what kind of extension is advisable.

I wanted to update the post here before going ahead with it now that I'm able to get better measurements.

Details:

For the main upper portion of the chimney, the inner dimensions are roughly 10x15.5" all the way down to the smoke shelf.

Minor dimensions shown below:
View attachment 265066


The view from the top of the chimney to the fireplace floor is relatively unobstructed until the smoke shelf. The height from the top brick surface to the fireplace floor is 15' 9".


View attachment 265068

In the photo below you can just see the edges of a paper plate on the fireplace floor between the smoke shelf (lower portion of photo) and a thin cast iron piece remaining from the damper assembly in the back of the fireplace that is proping up some fire bricks. A portion of the masonry that was chiseled out just above the in the first installation can be seen in the same photo.

View attachment 265070

Below is a look up the chimney from the fireplace at the same bottleneck after I removed the front damper plate with an angle grinder. This view shows the bricks that were chiseled out from the initial installation, the same thin cast iron bar from the above photo supporting a few fire bricks, and the lower surface of what I believe is a smoke shelf looking up the chimney.

View attachment 265069


The height of edge of the innermost portion of the smoke shelf (red dot from range finder in photo below) is 5' 4" above the fireplace floor.


View attachment 265072

A height of 5 feet 4 inches matches the top bricks of the mantle in the fireplace.

View attachment 265084

I used a small plastic canoe paddle with a minimum width of 6" and maximum width of 6-5/8" to test the bottleneck. The 6 inch portion seems to pass through fine, but the 6-5/8" is just barely too wide to fit through straight.

View attachment 265092


View attachment 265091

The 6-5/8" section of the paddle catches on the narrow dimension of the chimney at the location of the smoke shelf, but there is plenty of room in the other dimension.

View attachment 265095

Why not just run an oval flex liner the whole way if you can't clear enough there to make s round work?

 

[begreen]

There appears to be plenty of room for an insulated 6" round liner other than the bottleneck. If necessary can you knock out a couple of the smokeshelf bricks to keep it at 6" round all the way to the insert?

 

[riverfire]

> Why not just run an oval flex liner the whole way if you can't clear enough there to make s round work?

Good question. I'm trying to wade through pros and cons myself and don't currently have a strong preference. Here's a breakdown of my thought process:

* using pre-insulated components is very appealing to me for ease of installation and overall robustness in tight installations -- I haven't come across pre-insulated oval liners for some reason
* round seems to be preferred wherever possible and the oval-as-need Duravent approach seemed to lean in that direction -- I haven't come across any ballpark rules or models to help understand the impact these choices have on draft, which makes it feel like guesswork (15' oval vs 5' oval + 10' round (if there is no measurable difference between these two that would be helpful))
* I like the idea of the modular components for transport by boat and working on the roof (minor consideration)
* I believe I read smooth walled liners are less prone to creosote build-up and are easier to clean (although this may have been marketing literature -- I expect you have some thoughts on this)
* I was looking into a custom stainless steel chase cover as a simple and effective replacement for the crown I removed and these seem to be designed for round liners (minor consideration)

I may be overthinking this, but I'm erring on that side the second time around.

 

[bholler]

> Why not just run an oval flex liner the whole way if you can't clear enough there to make s round work?

Good question. I'm trying to wade through pros and cons myself and don't currently have a strong preference. Here's a breakdown of my thought process:

* using pre-insulated components is very appealing to me for ease of installation and overall robustness in tight installations -- I haven't come across pre-insulated oval liners for some reason
* round seems to be preferred wherever possible and the oval-as-need Duravent approach seemed to lean in that direction -- I haven't come across any ballpark rules or models to help understand the impact these choices have on draft, which makes it feel like guesswork (15' oval vs 5' oval + 10' round (if there is no measurable difference between these two that would be helpful))
* I like the idea of the modular components for transport by boat and working on the roof (minor consideration)
* I believe I read smooth walled liners are less prone to creosote build-up and are easier to clean (although this may have been marketing literature -- I expect you have some thoughts on this)
* I was looking into a custom stainless steel chase cover as a simple and effective replacement for the crown I removed and these seem to be designed for round liners (minor consideration)

I may be overthinking this, but I'm erring on that side the second time around.

If I were doing it and couldn't fit round I would use heavy wall or midweight flex liner ovalized to fit. It is smooth wall with no joints to deal with.

 

[riverfire]

> There appears to be plenty of room for an insulated 6" round liner other than the bottleneck. If necessary can you knock out a couple of the smokeshelf bricks to keep it at 6" round all the way to the insert?

That has also been nagging me. Now that the damper plate is removed, it seems to be *so* close! I found an outer diameter of 7.25" for the Rockford 6" pre-insulated liner. Perhaps with some chiseling and a nose cone it could work. I think the main thing stopping me was that I wasn't sure how to remove those bricks. The smokeshelf seems relatively inaccessible at 5' 4" above the fireplace floor (at least for an angle grinder), and I'm not sure what the risk of structural damage to the connected mantle bricks is for more heavy handed approaches. If this is commonly done I'd be inclined to give it a go.

Bottom up approach:

I might be able to chisel them with something like an oscillating multi-tool if I lie face up on a bench with a very good face shield, but that seems to be a good setup for a Darwin Award.

Top down approach:

Knock them out with a heavy weight on a rope?

What tools do people generally use for this?

 

[bholler]

> There appears to be plenty of room for an insulated 6" round liner other than the bottleneck. If necessary can you knock out a couple of the smokeshelf bricks to keep it at 6" round all the way to the insert?

That has also been nagging me. Now that the damper plate is removed, it seems to be *so* close! I found an outer diameter of 7.25" for the Rockford 6" pre-insulated liner. Perhaps with some chiseling and a nose cone it could it could wori. I think the main thing stopping me was that I wasn't sure how to remove those bricks. The smokeshelf seems relatively inaccessible at 5' 4" above the fireplace floor (at least for an angle grinder), and I'm not sure what the risk of structural damage to the connected mantle bricks is for more heavy handed approaches. If this is commonly done I'd be inclined to give it a go.

Bottom up approach:

I might be able to chisel them with something like an oscillating multi-tool if I lie face up on a bench with a very good face shield, but that seems to be a good setup for a Darwin Award.

Top down approach:

Knock them out with a heavy weight on a rope?

What tools do people generally use for this?

I use an electric demo hammer.

 

[riverfire]

> If I were doing it and couldn't fit round I would use heavy wall or midweight flex liner ovalized to fit. It is smooth wall with no joints to deal with.

That's helpful. I suppose all the connections required in the modular approach could be prone to buildup too. Just to be clear, Are you proposing manually ovalizing a 6" pre-insulated round liner as needed?

If so, then I'm more inclined to just buy the 6" pre-insulated round liner and aim for smoke shelf removal as Plan A with manual ovalizing as needed as Plan B, since it would use the same components either way.

My main reservation about ovalizing a 6" round liner was the smaller cross sectional area compared to the commercially available 6" compatible oval liners (7-3/4" x 4-3/4" or thereabouts). Perhaps it doesn't make much difference.

 

[bholler]

> If I were doing it and couldn't fit round I would use heavy wall or midweight flex liner ovalized to fit. It is smooth wall with no joints to deal with.

That's helpful. I suppose all the connections required in the modular approach could be prone to buildup too. Just to be clear, Are you proposing manually ovalizing a 6" pre-insulated round liner as needed?

If so, then I'm more inclined to just buy the 6" pre-insulated round liner and aim for smoke shelf removal as Plan A with manual ovalizing as needed as Plan B, since it would use the same components either way.

My main reservation about ovalizing a 6" round liner was the smaller cross sectional area compared to the commercially available 6" compatible oval liners (7-3/4" x 4-3/4" or thereabouts). Perhaps it doesn't make much difference.

Well my approach would be different than yours because I have an ovalizer. I would ovalize then wrap it. I would never recommend ovalizing without the proper equipment. And I don't know that you could ovalize preinsulated. I rarely use it so I have never tried. But I would upsized the liner to maintain volume if I was ovalizing unless the manufacturer allows a downsize.

 

[riverfire]

I believe I misspoke when I referred to the smoke shelf in the comments above. The protrusion is actually on the interior or front side of the chimney around the location of the mantle, and not on exterior side as shown in the diagram:

https://handmadehouses.com/wp-content/uploads/2015/10/smoke-shelf.jpg

I guess it is part of the general smoke chamber assembly construction

The big question is whether the chimney can afford to loose a brick at that location.

 

[riverfire]

I removed the rear damper bar and the bricks above it, which made just enough space for me to sit inside and access the bottleneck bricks with the the tip of the angle grinder. After a few iterations of grinding and picking I'm able to pass an 8" prop through it.



Now I'm confident there is plenty of room for a 6" round pre-insulated liner (8" OD or more). I'm glad I posted a follow up here. Thanks for the encouragement in this direction -- it should make for a much cleaner installation.

After reading through comments from @bholler and others in this thread on pre-insulated liners, I'd like to buy the thickest construction pre-insulated 6" liner I can get.

This seems to point to the Olympia Forever Flex 316L Hybrid Pre-Insulated model at 0.01 inches, which I believe qualifies as mid-weight.

The top-to-bottom height is 15' 9" and the Winterport height is 21.5" (w/ riser), so I need about (15 * 12 + 9 - 21.5) / 12 = 13.96 feet with 2 feet extra for the installation and a slight bend for a total of 16 feet.

 

[begreen]

Nicely done, That will make it much easier. Sometimes one just needs to be persistent.

 

[riverfire]

The 6" pre-insulated (8" OD) liner went down the chimney without a hitch.



Now there are some decisions to make about the collar-to-insert connection below.

The 6 inch collar center is offset 9 1/2" from the front, which gives about 9 1/2 - 3 = 6 1/2" inches of clearance from the fireplace surround to the front liner wall.

Going up, there are 9" of clearance from the collar to lintel and surround bricks (this is with the 2" riser bar installed underneath the unit). If I remove the riser bar I could have closer to 11 inches of clearance (see photo below for 9" clearance with 2" riser bar installed).

The collar and appliance connector will use up a couple of inches.

A right angle straight edge from the inner-most collar point up to the lintel shows the liner would require an additional 4 1/2" inches of lateral clearance for a straight-up-the-chimney connection (see photo below). Given the 9" vertical clearance from insert top to lintel, with roughly 2" for the appliance connector, that would leave 7" of vertical space for the connector to angle around the lintel. For a liner with an 8" OD that is probably not possible. This is allowing for the 2" riser bar that is recommended in the manual for cases with a floor level hearth. If I remove the riser bar, that would add 2" to for around 8 1/2" inches of clearance.

What are the downsides of removing the riser bar?

A bottom up view of the lintel and supported bricks is shown here. I could grind out a semi-circle (as needed) for the liner, and reinforce the remaining lintel + bricks with a custom plate. That would allow a very straight liner connection and would be optimal for draft.

In summary, it seems I have a a couple of options.

1) Connect the liner to the stove with the straight appliance connector, then pull the insert forward, bending the liner and grinding the lintel + bricks as needed until the insert is flush with the front bricks and surround. (I would likely want to reinforce the lintel with custom plate or welding to accommodate the missing semi-circle channel.)

[UPDATE: I found a comment from @bholler in this thread where he did exactly this (grind lintel then reinforce with welding).]

Since a straight-up connection would require approximately 4 1/2" of grinding, I'm guessing this might be reduced to 2 1/2" or 3" of grinding after gaining additional clearance from bending the flexible liner over the (less than) 9" span of vertical clearance. Perhaps the lintel + bricks could be reinforced with a larger welded plate after grinding out a semi-circle for the liner. As an extension of this path I could remove the recommended 2" riser bar to gain another two inches of vertical clearance for bending the liner. I'm unclear on the importance of the riser bar.

2) Replace the straight appliance connector with an angled connector.

This would seem to be the easiest option. Surprisingly, I'm having trouble finding a low profile angled chimney liner appliance connector that is similar to the product shown below, but with a built in 30 degree angle (or similar).

Does anyone make such a product?

[UPDATE: After posting, I believe I found an angled appliance connector from Rockford that will attach to the collar (below). I'm still interested in any suggestions for low profile elbows -- these use up a fair amount of vertical space.]

I have seen very low profile angled "boot adapters" that seem very close to what I'm looking for, but they seem to be intended to create a collar for an open insert vent, and screw to the the top surface rather than mount to an existing collar.

3) Install the liner to the collar as is and pull it forward as far as it will go -- this will leave the front of the insert a few inches back from the surround.

It would prevent a clean setup for the the surround plate assembly, but perhaps I could have some custom surround plate made to seal the gap (a 3D variant of the plate below). Has anyone done this?

 

[bholler]

That looks like a 30 degree elbow would fit in there easily.

 

[RSNovi]

I had a custom plate made for mine. It worked well.

 

[riverfire]

That looks like a 30 degree elbow would fit in there easily.

I've ordered a 30 degree version and will give it a try.

The height (B) is 10 inches, and the offset (C) is 5.25 inches.

I had a custom plate made for mine. It worked well.

Can you share a photo? The elbow seems quite a bit taller than it has to be. The male and female connections can't be reduced, but there are a few inches in the middle that could be eliminated. The closest thing I've seen to this is the boot adapter wedge shape. Perhaps that could be adapted to fit a collar.

 

[bholler]

I've ordered a 30 degree version and will give it a try.

The height (B) is 10 inches, and the offset (C) is 5.25 inches.

Can you share a photo? The elbow seems quite a bit taller than it has to be. The male and female connections can't be reduced, but there are a few inches in the middle that could be eliminated. The closest thing I've seen to this is the boot adapter wedge shape. Perhaps that could be adapted to fit a collar.

Just trim the male end down.