Do I need a SS liner or not?

[80s Burnout]

I am looking to install a Jotul Castine wood stove. This stove has a 6” flue collar. My chimney has a 7” x 14” clay flue liner from 1940 and it is a center chimney - its only exposed to outside above the roof line. Jotul manual says that the crss-sectional area should not be more that 3x the 6” flue collar (or 18").....so I pass that test. But it then says the flue should not have a nominal size greater than 8” x 8”.....do I pass that test? Then it says the clay flue liner should not exceed 8” x 12”....seems like I fail that test at 7” x 14”, but just barely.

Do I or do I not need a stainless liner to run the full length of the chimney? Sounds like I’m close to not needing one. What are the risks and performance issues if I don’t install a full-length liner from stove to top of chimney?

Your thoughts and suggestions are much appreciated.

Thanks.
Burnout

 

[Jimbob]

What are the risks and performance issues if I don’t install a full-length liner from stove to top of chimney?

Your thoughts and suggestions are much appreciated.

Thanks.
Burnout

The risk could be a chimney fire. Although chimney fires do sometimes happen in lined chimneys, they are less likely to spread to the rest of the house.
A stainless lined chimney will stay cleaner, and be easier to clean whan needed.

 

[Dustin]

Better draft.

No risk of leaking CO into your house


Lowered risk of chimney fires. Granted, you have a smaller opening for the smoke to exit now, but if you stay on top of things, and clean your chimney (which would then be waaaay easier to do) you'll be fine.


Every single chimney fire I have ever responded too in the last 7 years as a volunteer firefighter have all been in UN-LINED masonry chimneys.

Not one, seriously, one in a lined, or double wall rigid chimney.

 

[BrotherBart]

I burned my Jotul F3 CB into a 8X12 OD clay flue 30 feet tall for one season and the draft was pitiful. For the next season I ran a full length flex liner in that flue and it was like getting a new stove. The first year I could not for the life of me get that stove up to temp. Now I have to hold it back. That sucker just wants to GO.

In fact it is sitting over there cruising right now. Gonna get cold here tonight. We are wimps around here and we think 40 degrees is cold and don't want anything to do with it.

 

[fossil]

The cross-sectional area of a 6" flue is 28.27 in^2. A 7" x 14" flue has a cross-sectional area of 98 in^2. That's an increase in area of a factor of 3.47. You fail the test. Install a liner. Thank us later. Rick

 

[Beanscoot]

"Jotul manual says that the cross sectional area should not be more that 3x the 6” flue collar (or 18").....so I pass that test."
Oops, a mistake in algebra there. The area of a circle is pi x radius squared, so about 28 square inches. Three times this is 84 sq in.

Your flue of 7” x 14” has an area of 98 square inches, or three and a half times the area of a six inch round flue.

 

[Beanscoot]

Aargh... the Cap'n beat me to it while I was cypherin' without my slide rule.

 

[North of 60]

We are wimps around here and we think 40 degrees is cold and don't want anything to do with it.

I guess theres no chance in hell your gonna make it here for Chistmas to deliver my oak . Hey uncle B. :cheese:

 

[fossil]

I guess theres no chance in hell your gonna make it here for Chistmas to deliver my oak . Hey uncle B. :cheese:

Airlift is scheduled for late on December 24th. Make sure the smudge pots along the sides of the runway are burning. (Yes, I'm BB's flight scheduler.) %-P Rick

 

[unit40]

I burned my Jotul F3 CB into a 8X12 OD clay flue 30 feet tall for one season and the draft was pitiful. For the next season I ran a full length flex liner in that flue and it was like getting a new stove. The first year I could not for the life of me get that stove up to temp. Now I have to hold it back. That sucker just wants to GO.

In fact it is sitting over there cruising right now. Gonna get cold here tonight. We are wimps around here and we think 40 degrees is cold and don't want anything to do with it.

Now, I have had totally different results with my 3CB's. Basement stove runs into an 8 x 8 clay flue and runs like a charm. My first floor stove runs through the block off plate into an 8 X 12 clay liner and I wish sometimes I could slow the thing down. These stoves are running up a center chimney through the second floor, attic, then probably another 6 feet or so over the roof. I looked at the Jotul manual last night. I need a minimum 8x8 and a maximum 8x12. So I am good, except for the fact that I never checked the specs before I bought and installed the stoves. Thought all I needed to do was hook up the pipe and I was good to go. I was lucky.

 

[80s Burnout]

Thanks folks for this feedback. My algebra was never any good. Looks like I'll be put up the $$ for a liner, which is fine. I want this baby to cook.

Regards,

 

[BrotherBart]

I think the simplest answer to the "do I need a liner" question is that the majority of stoves today are designed, tuned and tested to provide their optimum performance with a six inch pipe. So it would follow that any other venting solution has a high probability of not getting the best performance from the stove.

In fact it would be kinda counterproductive to spend tons of time studying burn times, particulate emissions numbers, user experiences et. al. and then proceed to hook the winner up to anything other than its optimum design flue configuration.

 

[astrodon]

This is my second year burning, so I am still searching for enlightenment on the subject of a SS liner.

I have a 30-NC in my basement with the 6" pipe going through a clay thimble into a 8x10 (inside) clay lined flu. The chimney is an inside one with three flues, about 24' from thimble to crown, with 4 or 5 feet above the roof line. The clay liners and brickwork above the first floor were new from the previous owner. When I installed last year, I was told by the guy that did my chimney/masonry work that a SS liner would run me about $1000, maybe more, because of the narrow bend in the flu where it apparently went around the fireplace's middle flu on the first floor. He recommended just running the 6" pipe into the thimble with stove gasket rope tucked in around it to see how everything worked. He also recommended checking/cleaning the flu every 6 weeks for signs of improper operation, which I did.

To make a long story short, my flue only has a slight glaze on it , both at top and on the bottom, after being swept by me only 3 times. You can see the clay through the glaze, and it appears to be the result of my first month or two of burning as it does not appear to be getting any worse. I was also burning slightly moist wood for part of the year last year. During the colder months last winter, I had some difficulty keeping the stove below 700 to 750 with the air control only barely open at approximately 15%. A few times I had to put foil over the air inlet to head off a runaway overfire. I am afraid that if I put a SS liner in that I would have serious over-draft. The only sign I have of possibly poor draft is the door glass hazes up around the bottom. But I think this has more to do with a slightly weak door seal at the bottom of the door (a dollar bill will wiggle slightly along the bottom, and I have to "fluff up" the gasket there to keep it tight).

I have drier wood this year, and I am more experienced with my stove as well. So, given all of the above, I am going to go without again this year and keep an eye on things.