Ovalizing Steel liner - okay to do?

Ovalizing your own liner is fine, and can be done fairly easy. Either by rolling a pipe over it, starting at the end or taking a 2x10 or 2x12, 24" in length and again starting at the end press down, moving it along the liner. Kneel with the liner between your legs and usually, you only need to do 18" to 24" to get it through the damper. After it is installed, just reform the very end of the liner back to round, and attach your connector on to that.

Isnt ovalizing your liner going to give you a smaller volume pathway? That is why I would never do it. The manufacturer ovalized liner has the appropriate internal volume.

CTwoodburner said:

Isnt ovalizing your liner going to give you a smaller volume pathway? That is why I would never do it. The manufacturer ovalized liner has the appropriate internal volume.

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How so? You don't change the internal volume by reshaping it(short of smashing it flat). What you lose in in one direction, don't you you pick up in another at least to some extent?
Joe

All reshaped liners, whether they are oval, square, or rectangle start out as round. Yes by changing the shape of a liner you also change the sq in area. But when you only have a certain size to begin with, you have to make do with what you have. So for instance a 6" liner will have about 28 sq in area, to maintain that same area you will have to go to a larger liner when ovalizing to maintain the same area. Bottom line it has to fit inside the flue, and still make your appliance draft and perform well. You do have options, but choose wisely.

polaris said:

CTwoodburner said:

Isnt ovalizing your liner going to give you a smaller volume pathway? That is why I would never do it. The manufacturer ovalized liner has the appropriate internal volume.

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How so? You don't change the internal volume by reshaping it(short of smashing it flat). What you lose in in one direction you pick up in another.
Joe

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Polaris:

It seems like "squashing" the liner wouldn't change anything. But what it does change is the cross-sectional area.

This is from Simpson DuraVent: "NOTE: Ovalizing reduces the cross-section area of a liner." And from Ventinox VHF HiFlex 321-Alloy Stainless Oval Relining Pipe. "These Oval-to-Round lengths can be convenient in certain situation. However, since ovalizing always reduces the cross-sectional area, be sure you don't use it to downsize your liner to less than the size of the flue collar on the appliance. That would violate NFPA 211."

HOW TO USE THE CHART ABOVE - AN EXAMPLE: When 6" round Ventinox liner is ovalized so that its minor (small) dimension is 4", then its major (large) dimension will be 7.7" (or slightly larger) and its cross-sectioned area will be 24 sq. in.

ORDERING NOTE: Custom ovalizing does not produce a perfectly even oval shape. The major dimension may be slightly larger than indicated on the above chart. Please allow for variances when ordering.

PRODUCT NOTE: Avoid downsizing your liner system - always keep the cross sectional area of ovalized liner the same, or larger, than the cross-sectioned area of the appliance outlet. In other words, the cross-sectioned area of your ovalized liner (from the table above) should always be equal to or greater than the cross-sectional area of the round pipe that fits the appliance outlet (from table below).

polaris said:

CTwoodburner said:

Isnt ovalizing your liner going to give you a smaller volume pathway? That is why I would never do it. The manufacturer ovalized liner has the appropriate internal volume.

Click to expand...

How so? You don't change the internal volume by reshaping it(short of smashing it flat). What you lose in in one direction, don't you you pick up in another at least to some extent?
Joe

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Slightly ovalizing a cylinder will marginally reduce its volume (and cross-sectional area) if you had to ovalize the whole thing. More likely than not the draft impact is minimal. If you had to SEVERELY ovalize it, some high-school maths might be needed to figure out how much larger a liner you'll need, so that you have sufficient cross-sectional area AFTER its been squashed.

Mmmm... squash. I want a turkey dinner now.

polaris said:

CTwoodburner said:

Isnt ovalizing your liner going to give you a smaller volume pathway? That is why I would never do it. The manufacturer ovalized liner has the appropriate internal volume.

Click to expand...

How so? You don't change the internal volume by reshaping it(short of smashing it flat). What you lose in in one direction, don't you you pick up in another at least to some extent?
Joe

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To some extent. It does get smaller. A circle has the highest area for a given circumference, so getting away from a circle loses area/volume.

Think of it this way, If you squeeze it all the way flat it has no volume, even though it got larger in 1 direction. Perfectly round is largest, anything less than round has a lower volume.

a few feet at 4.5 inches aint a big deal. We always chop open the damper prior to ovalizing, but will squish a few feet if needed.

Franks said:

a few feet at 4.5 inches aint a big deal. We always chop open the damper prior to ovalizing, but will squish a few feet if needed.

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While I agree it MAY not be a big deal, the ovalizing gets thrown around here so much I thought it worth comment. There is a reason why factory oval liners have larger outside dimensions and the same inside volume as the comparable round liner. IF I am doing a nee install, I am going to install the liner, what I would consider, properly. I would have installed 6" insulated flex liner upstairs for the Castine but did not want to cut that damper out and have to chip some brick. I installed the Duraliner with the oval flex section through the damper.

I'm reading the posts above and trying to understand what's considered acceptable. Is it ok for me to ovalize my 6 inch liner to squeeze it past the flue? It will need to be squeezed down about 2 inches total (1 inch on each side) to get it to fit.

bholler said:

You should cut the damper frame to make it fit right ovalizing reduces volume and makes it more difficult to clean. It is far better to cut the damper frame and keep it round. To answer your question yes you can ovalize it but that should be a last resort.

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This is your answer right here. It sums it up perfectly!
Just cut that damper frame out of the way. It's not a big deal at all. If someone wants to restore the fireplace they can just install a lock top damper, you will be doing them a favor.

Sounds like a slammer install to me. Hope your lining that thing all the way to the top.

I cut the damper and chipped a few firebrick out and got my 8 inch ss liner in no problem and installed t clean out

As far as I am concerned even a direct connect is a slammer.
I know terminology, but still not something I would do or recommend.
I may be reading wrong, but he said he has a "short section" of flex.
So he is either terminating as a direct connect, or coupling to another section of liner.
Hard to tell by the description.

Very nice block off plate work Ex.

Something that hasn't been mentioned regarding "ovalizing" a ss flex liner is the possible integrity damage to the liner. I haven't had any direct experience trying to ovalize a flex liner, but while installing my flex liner it seemed to me that these liners are so thin it wouldn't take much to damage them while trying to mash them down to a shape that can be forced through a standard fireplace damper opening. Since this ovalilzing is being done down near the stove connection it is going to be the hottest part of the flue once the stove is fired up. I wouldn't want to put that sort of stress on the liner.

I wouldn't do it for many reasons, and all but one have been mentioned.

My last reason is that you cannot completely clean an ovalized liner. Without completely cleaning it, you have no idea what you are leaving in there to sit and collect over time.

I agree with hogwildz: It sounds like a direct connect. I know they are legal and many people do it this way, but I just wouldn't.

bholler said:

That being said doing it without the proper equipment there is no way to get it uniform so both of those are a concern.

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That's why I would never ovalize a liner

I couldn't agree more with your comments above.