is a flue liner needed

[islandfarmer]

i an replacing a old defiant with a kodiak 1700 the idea being that a EPA stove will give more heat with less wood. i have an exterior chimney with a 6 1/2 x 10 in. clay flue .. it is 21 ft from the bottom of the thimble to the top of chimney. i have a flat roof and the chimney extends 4 ft above the roof. do i need to but a liner in the 6 1/2 x 10 in flue? will one fit? will the ridges in a liner slow the draft? the clay thimble is 7 1/2 in in diameter can i but a double wall 6 in pipe through it to a liner?

 

[bholler]

do i need to but a liner in the 6 1/2 x 10 in flue?

possibly depends on the chimney and the stove.

will one fit?

yes but it may not be easy

will the ridges in a liner slow the draft?

A little but not much you could go with heavy wall or rigid which are smooth

the clay thimble is 7 1/2 in in diameter can i but a double wall 6 in pipe through it to a liner?

do double wall just bring the tee snout out

 

[Nick Mystic]

My Woodstock Classic, down in the lower level of our house, vents into a clay tile flue similar to the description of your current set up. My stove vents out the back into a 90 degree elbow and then up about 30 inches with another 90 elbow into a clay thimble to the flue. The stove draws fine and the chimney stays so clean I've never even swept it in over ten years. However, the big stove is upstairs in the living room where we spend most of our time. The Woodstock is in the downstairs den, which is basically my man cave. I'll watch some football games down there in the winter and burn a fire then, but most of the time it's just one or two fires a week in that stove. At any rate, it could be worth a try venting directly into your clay tile flue if it's sound and see how the stove burns. If it doesn't work out you haven't lost much and can proceed to Plan B and install the flex liner. If it does work out you will save yourself a lot of money and extra work.

 

[NVHunter]

I'm in the same exact position as you. I have 20 foot 7" x 11" clay flue which services the daylight basement woodstove thimble. I've had one sweep (who doesn't install liners) and two installers stop by to look at the flue and see if I can put a liner in.

Non installing sweep said flue looks great and if I want a liner it can be done. (I have two offsets to go around the fireplace above the thimble on the first floor).

The second company to come out was recommended by the above sweep. Suppose to be the top guys in town... They showed up 50 minutes late and then looked at the flue from the thimble hole for 3 minutes and said, nope no way to put a liner in. Then tried to sell me a gas or pellet stove saying that's all that will work there....

Last guy came out and said the flue is in bad shape but he will be able to put an oval liner in the flue. Said its going to be tuff to do but its do-able. Says the tiles were not put together well when it was built...

Crazy how different the opinions are between these three companies and the middle one just plan and simply pissed me off... Who to trust....

Anyway. From my research your stove will function better with a liner and much better if insulated. That's why I'm going to go with an ovalized liner (4.5"x9.1" to keep the required 28 square inches for the 6" flue).

 

[Hogwildz]

Install the liner and insulate it.

 

[bholler]

Last guy came out and said the flue is in bad shape but he will be able to put an oval liner in the flue. Said its going to be tuff to do but its do-able. Says the tiles were not put together well when it was built...

That is the one that sounds right to me . That is typically what we run into with flues that go around a fireplace. but i didn't see it so i cant say. The problem is even if it is in great shape it is still way oversized for most modern stoves.