Woodstove fireplace insert question, actually 6"reliner question..

[reiserrob2003]

I want to install a wood burning f/p insert in my existing masonry fireplace, I've been told the best way to do it is to use a 6" s/s flex relining kit right to the top of the existing masonry chimney. I climbed to the roof today to measure the existing tile flue and was surprised to see a dimension of 6"x10" i.d rectangular clay flue. If the unit calls for a 6" flue and the existing flue is already exactly 6" wide how will I be able to make that work. Seems to me the 6" s/s liner will probably be a little over 6" and end up being to tight a fit to get it down the tile flue. Is it possible to use an adapter connection (6" to 5"reducer) and run 5" flex liner up to the top or is that a no, no? Do they even make reducers and if it is possible how would it effect the operation the the stove? Or should I consider a direct connection to the old flue and how will that effect the operation of the stove. By the way its going in the basement of a raised ranch and the chimney is on a exterior wall and is appx. 20 ft. high

 

[DAKSY]

Ovalize your liner enough to get it down your chimney & then
squeeze it back to round where it meets the stove adapter.

 

[theheatelement]

Many people will use either a 5.5 or 5. Their are some inherent problems with ovalizing. Smoke goes up in a spiral and being that an ovalized liner is not round you might not draft more then a 5 inch liner. The outside diameter of a pipe is generally 3/8 bigger then the size of the pipe. I would run a 5 in liner and use a liner to stove adapter that takes a 5 3/8 liner outside to 5 13/16 o.d. for inside the stove lip.

 

[oconnor]

Many people will use either a 5.5 or 5. Their are some inherent problems with ovalizing. Smoke goes up in a spiral and being that an ovalized liner is not round you might not draft more then a 5 inch liner. .....

Smoke goes up in a spiral? If so, is there an up and a down to the twist in a flex liner to make sure the rotation directions of the smoke and the liner are the same, and do you have to take Coriolis Effect into account depending on whether you are in the north or south hemisphere? While it may spiral, I'm not sure the spiraling is relevant to any flow rate reduction that occurs with an oval liner.

reiserrob2003:

I would not go down to a 5 inch from 6 unless you absolutely need to - the drop from 6 to 5 inch is a one third reduction in cross section - a major restriction to flow rate. Ovalizing a 6 inch, or purchasing a rectangular flex liner may not flow as well as it's circular cousin, but it will flow better than a 5 inch will.

I ran a 5 inch on my insert all last winter, and had smoke spillage issues on most reloads. Had a 6 inch installed a few months back, and no problems any more.

 

[CarbonNeutral]

Simpson makes a pre-insulated rigid liner that just happens to have a cross sectional area equivalent to 6", but whose thinest dimension is less than 5"...

There was a somewhat lively discussion on page two of this post:

https://www.hearth.com/econtent/index.php/forums/viewthread/39883/

where I embark on a discussion about aspect ratios, pressure differentials, and how the narrower aspect ratio of the oval makes bugger all real difference compared to the round flue. I also don't buy the spiraling smoke. The only thing I found on a quick search was an unreferenced comment from This Old House. There's no reason I can think of why it would spiral - I would guess just some plain old turbulent flow is what is going on, unless the stove is putting a spin on the gases that is somehow maintained through twists and tees - I don't reckon so.

 

[boostnut]

I'd look into a 5.5" liner. It is a very slight reduction in size (which I doubt will have ill effects on your stoves performance) and I would think it will be much easier to sweep than an oval. Call the stove manufacturer to verify the 1/2" reduction with a 20' run is acceptable.

 

[Fsappo]

I concur with the 5.5" liner idea. I guess it would help to know how many cubic feet the firebox was.

 

[CarbonNeutral]

Doubt there's much difference between the 5.5 and 6", but you're not getting an insulated 5.5" down a 6" flue...

For the brush, I', just going to buy an 8" brush and trim it to size.