Drafting in a 5.5 Inch Liner on a 6 Inch Collar ( Jotul Oslo )

[Mr. MojoRock]

Hey there, everybody. New to the forum, here, and having fun looking through all the conversation. I've spent a lot of time looking for an answer to my question below. I found a thread that I was hoping to have some updated info on ( it's 7 years old and equipment may have changed ).

I've recently gotten a Jotul Oslo and we're having to install a new chimney liner. Guys tried to install a 6" flex liner today into a 8x12" existing clay chase but they were getting hung up after about 8 feet.

It's clear that you shouldn't downsized a flue liner based on the diameter of the collar - but I'm wondering if there's any update to downsizing a liner .5 inch ( 6" to a 5.5" ) with 25 feet of flue space.

Is there a considerable impact on draft and or the safety while running the Oslo at full steam?

Thanks for any help or advice.

 

[Squisher]

With 25' I think you'd be fine. I've got about 23' to my basement stove(PE Summit) on a 5.5" liner uninsulated. It works fine for me, but mine is an interior chimney too, which is an advantage. If your chimney is on an exterior wall you may want to consider having the clay liners busted out to fit a insulated 6" or look to a ovalized insulated liner like duravent.

They make a product called duraliner and the 6" equivalent oval is 4 3/4" x 7 3/4". It's in sections rigid or flex. The rigid sections are insulated at that dimension and the flex sections are uninsulated at that size. I wrapped 1/2 insulation on the flex section and was able to fit it down a 6"x13" chimney. The oval I'm mentioning is a six inch equivalent, I used this on my upstairs insert.

If you're jamming a uninsulated liner down your existing chimney, try to make certain it's up to code, otherwise it still won't be up to code. Insulating a liner will bring a out of code chimney up to code(for clearances to combustibles) and provide superior performance. Win win.

 

[Mr. MojoRock]

Appreciate the quick reply here, Squisher.

Liner does happen to be uninsulated but it's an interior chimney, aside from the 5 feet exiting the building. Guys who were trying to install this didn't seem the most competent and gave up after 30 minutes, but there is a big corkscrew turn towards the bottom of the stack that I think was freaking them out.

I called another shop that recommended the 5.5 inch. I know Jotul doesn't recommend it, but have you found there to be major drafting issues with your undersized liner? Did you have to install any top mounted dampeners to adjust the flow?

Thanks again!

 

[Squisher]

With the undersized liner draft will be weaker. So less likelihood of needing a damper. I don't use/have a damper and my draft is fine. I burn only seasoned wood though. My basement stove operates fine, but you could get into some smoke spillage trouble if you weren't burning properly when the chimney is coolish and outside temperatures are warm(weak draft). On the other end of the spectrum when its cold out and running hot I can almost get myself in some trouble of a runaway fire where a damper might be handy(strong draft). But if proper temps and burning techniques are adhered to it works flawlessly.

I'm not very familiar with jotul's so can't speak to whether they are very 'easy breathing'. The PE's are renowned easy breathers so that could be part of why I don't have any issue with a downsized liner. Hopefully some others here who are more familiar with your stove will pipe in.

 

[Squisher]

Also a six inch liner(I knew it was uninsulated from your original post) will not fit down a six inch x anything clay tile. So if they got it in 8' they were doing good. Lol.

 

[Squisher]

You threw me a bit with the word 'chase'. This is an interior masonry chimney with a clay tile liner? If so I think that will go along ways towards making a undersized uninsulated liner work ok.

Do note that an interior masonry chimney is supposed to have 2" of clearance to combustibles all the way up. If your existing chimney doesn't have this it is not to code and still won't be after putting a uninsulated liner in. A common upgrade is to bust out the clay liners to accOmadate a insulated liner of the proper,size. This would greatly improve performance(draft) and safety. And would bring the chimney to code. A properly insulated liner in a masonry chimney negates the need for clearance to combustibles on the outside of it. It becomes zero clearance to combustibles.

 

[Mr. MojoRock]

With the undersized liner draft will be weaker. So less likelihood of needing a damper. I don't use/have a damper and my draft is fine. I burn only seasoned wood though. My basement stove operates fine, but you could get into some smoke spillage trouble if you weren't burning properly when the chimney is coolish and outside temperatures are warm(weak draft). On the other end of the spectrum when its cold out and running hot I can almost get myself in some trouble of a runaway fire where a damper might be handy(strong draft). But if proper temps and burning techniques are adhered to it works flawlessly.

I'm not very familiar with jotul's so can't speak to whether they are very 'easy breathing'. The PE's are renowned easy breathers so that could be part of why I don't have any issue with a downsized liner. Hopefully some others here who are more familiar with your stove will pipe in.

Thanks for this. These things are dialed in from the manufacturer, huh? I'd imagine a .5" difference wouldn't make that much of a difference but man, they're spot on? This is my first Jotul so I'll let ya know!

 

[Mr. MojoRock]

You threw me a bit with the word 'chase'. This is an interior masonry chimney with a clay tile liner? If so I think that will go along ways towards making a undersized uninsulated liner work ok.

Do note that an interior masonry chimney is supposed to have 2" of clearance to combustibles all the way up. If your existing chimney doesn't have this it is not to code and still won't be after putting a uninsulated liner in. A common upgrade is to bust out the clay liners to accOmadate a insulated liner of the proper,size. This would greatly improve performance(draft) and safety. And would bring the chimney to code. A properly insulated liner in a masonry chimney negates the need for clearance to combustibles on the outside of it. It becomes zero clearance to combustibles.

As far as I can tell it's to code. And yes - it's an interior masonry chimney with a clay liner. I've got a hole cut through the plaster + lath above the mantel and it's got the clearance. One thing I'll need to figure out is if I'll run into any flack from the inspector having a .5" smaller pipe ( we have to have the building inspectors greenlight stove use down here ).

 

[BrotherBart]

I run one stove with a 23 foot 5.5" liner and one with a 30 foot 5.5" liner. Both not insulated and in 8X11 flue tile external masonry chimneys. No problems so far. But they have only been heating the place since 2006 so we shall see.

And the inspector won't have a clue what the diameter of the liner is.

 

[Squisher]

Lol. Make sure to update us when you've done more complete testing on those setups.

 

[Mr. MojoRock]

Good to know @BrotherBart - thanks. With an external chimney have you seen there to be a variance in drafts when it's colder outside versus warmer as @Squisher mentioned above?

 

[Mr. MojoRock]

Here's hoping the inspector has zero clue!

 

[BrotherBart]

Draft is gonna vary based on the temp outside the top of that chimney versus the temp in the house. A deferential thang.

 

[BrotherBart]

Here's hoping the inspector has zero clue!

He won't unless you bring it up. Mine had never seen a chimney liner and I had to sit him down and give him a fifteen minute class on them. I threatened to keep the fee for the education.

 

[Mr. MojoRock]

Wonder if it's a smart move to insulate the top of the liner that's sitting above the roof line....
May be overkill to install a damper plate at the cap. I'll poke around and see if anyone's done that in here.

 

[BrotherBart]

Wonder if it's a smart move to insulate the top of the liner that's sitting above the roof line....
May be overkill to install a damper plate at the cap. I'll poke around and see if anyone's done that in here.

I stuffed mine down to the roof line with rockwool insulation. It helps. Don't even think about a damper at the cap. Somebody not knowing it is there and starting a fire would be your worst nightmare.

 

[Mr. MojoRock]

Good call with the rock wool. I'll stuff that in there real good

 

[Squisher]

Stuff the roxul in and then seal the top plate.

 

[rdust]

Running on a 5.5 liner here, 27' of liner and 3' or so of double wall stove pipe. I've had a Lopi Endeavor on it and currently a BK Princess.

With a 25' chimney my guess is it will be ok.

 

[Woody Stover]

I think the Oslo is a little picky about draft but I'd guess you'd have no problem at 25'.