Liner sizing question

LONDONDERRY · Sep 3, 2008

So yesterday I was researching on sizing a liner for my exterior chimney. The flue size is 6-1/2 x 10-1/2 chimney is 15ft-6inches and the stove insert has a 6" diameter. I called a few places and I got two suggestions that I need an opinion on from everyone before I place an order today.

First advice I got was to use a 5-1/2" diameter flex liner and place an reducer at the stove pipe end. Because of the fule being small, I will not be able to add an insulation wrap.

Second advice I got was to use a 6" diameter flex liner and reshape it slightly to be oval in the mid-section, which will decrease it to less the 6" diameter.
Any suggestion which option to go with?

All so, from the top of my chimney crown to the bottom of the hearth is 15'-6". Some places sell flex liners in 15' and 20 lengths, which size would you recommend? All so I notice some are smooth wall and some not does this really matter or not?

Thanks
Frank

pulldownclaw · Sep 3, 2008

Why do you need to reduce the liner, to fit through the smoke shelf in the chimney? I bought a 20' 6" flex liner online, but should've gotten the 25'. You should get the 20', you will need the extra for any twists and turns and for where it comes out the top. Hope some others chime in for you.

LONDONDERRY · Sep 3, 2008

pulldownclaw said:
Why do you need to reduce the liner, to fit through the smoke shelf in the chimney? I bought a 20' 6" flex liner online, but should've gotten the 25'. You should get the 20', you will need the extra for any twists and turns and for where it comes out the top. Hope some others chime in for you.

Well the clay liner is 6-1/2 x 10-1/2, but they are not all lined up, there is some jog in them when I flashed a light down the chimney. So when I talked to a sales person they mentioned that I might want to use a 5-1/2 liner instead, but I should call the stove manufacture first to see if a 5-1/2 liner is okay to connect to a 6 in diamter stove pipe. However, when I talked to another saels person at another company, he suggested going with a 6 in diamter flex liner and sqwashing the mid section if need be to reduce the diamter down to snake it down the chimney liner. So what is the better option, go with a smaller diamter felx liner or sqwash the liner

pulldownclaw · Sep 3, 2008

What kind of stove do you have? I know my Hampton insert manual said I could use a 5.5 or 6" liner.

BrotherBart · Sep 3, 2008

The issue with liner size is total cross sectional area. Before fossil shows up with his slide rule I will take a shot at answering the question.

A six inch round ID liner has a cross sectional area of 28.46 sq inches, perfectly ovalized it will have a cross sectional area of 24.60 inches. A 5.5" round liner has a cross sectional area of 23.758 sq. inches. Given that somebody squashing an expensive piece of liner in their shop or backyard does not have a prayer of getting it perfect there is probably going to be something less than an area of 24.60 in the ovalized pipe.

Ergo, using the perfectly round 5.5" liner is going to give you approximately the same cross sectional area as ovalizing a 6" liner. Without the risk of wrecking the liner trying to mash it down. And a round brush will be able to make contact with all of the surface of the round liner come cleaning time. You don't even want to know how much oval brushes cost.

Does this say that you won't have draft problems with a 15 foot chimney? No. But it does say that you would probably have them with an ovalized liner just the same.

fossil · Sep 3, 2008

BrotherBart said:
...Before fossil shows up with his slide rule I will take a shot at answering the question.

Too late, I'm here...but I have nothing to add to your thorough and sound response. ;-) Rick

LONDONDERRY · Sep 3, 2008

BrotherBart said:
The issue with liner size is total cross sectional area. Before fossil shows up with his slide rule I will take a shot at answering the question.

A six inch round ID liner has a cross sectional area of 28.46 sq inches, perfectly ovalized it will have a cross sectional area of 24.60 inches. A 5.5" round liner has a cross sectional area of 23.758 sq. inches. Given that somebody squashing an expensive piece of liner in their shop or backyard does not have a prayer of getting it perfect there is probably going to be something less than an area of 24.60 in the ovalized pipe.

Ergo, using the perfectly round 5.5" liner is going to give you approximately the same cross sectional area as ovalizing a 6" liner. Without the risk of wrecking the liner trying to mash it down. And a round brush will be able to make contact with all of the surface of the round liner come cleaning time. You don't even want to know how much oval brushes cost.

Does this say that you won't have draft problems with a 15 foot chimney? No. But it does say that you would probably have them with an ovalized liner just the same.

Thank you for the advice. It seems that based on logical sense going with a 5.5 in diameter flex liner will do. Based on some calculations:
6"dia x 180" lg pipe is 11.78cu-ft
5.5" dia x 180" lg pipe is 9.9 cu ft

I still don't know if this will be a draft issue or not

LONDONDERRY · Sep 3, 2008

So I'm going to purchase a 5-1/2 felx liner. However the stove fitting is 6 in diameter. Should I buy a reducer or an enlarger? All so I could not find a 6 x 5.5 size only a 6 x 5. Does anyone know if the 6 x 5.5 exists?

Frank

BrotherBart · Sep 3, 2008

Tell the liner kit vendor that you want the kit with a stove adapter for a six inch flue collar connection to the 5.5" liner.

Randyb · Sep 4, 2008

Ok, this is to those who use slide rules and for those of us who now think we may be arithmetically challenged, I know I'm not spelling challenged though! Anyways, if I take a round 6" diameter pipe and ovalize it, how does this decrease my crossectional size? Or is it just my understanding of what is meant by crossectional, where my misunderstanding lies?

As far as finding 5.5" liner forever flex has it or most of the links on the site have the kits avail.

fossil · Sep 4, 2008

You could ovalize it to zero if you beat on it hard enough. Rick

BrotherBart · Sep 4, 2008

RandyB said:
Ok, this is to those who use slide rules and for those of us who now think we may be arithmetically challenged, I know I'm not spelling challenged though! Anyways, if I take a round 6" diameter pipe and ovalize it, how does this decrease my crossectional size? Or is it just my understanding of what is meant by crossectional, where my misunderstanding lies?

As far as finding 5.5" liner forever flex has it or most of the links on the site have the kits avail.

Do a little looking around on Google for the area of an ellipse. That is what a circle turns into when you squash it.

Virtually all liner peddlers have 5.5" available. Forever Flex is distributed by Olympia Chimney Supply and sold by a buncha people.

KateC · Sep 5, 2008

Hijacking here because I don't want to start another liner thread---is there any conceivable reason to use an 8" and ovalize it rather than use a 6" round? That seems to be what my installers did and they had to squash it beyond the point to get good draft and now we're having to fight them to fix it. It's a 15ft. exterior masonry chimney and the insert has a 6" opening at the top.

Sorry if I should have started another thread but it's kind of an off-the-cuff question.

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