Anything wrong with an oval liner? My damper is 5 3/4 wide, I see they make oval liner 5 1/2 x 6 3/4 wondering if I could get it past the damper without having to cut it and just transition it to the 6" opening on the insert. Thanks in advance!
Other than the price, no, not really. A little harder to work with for install...harder to clean well too...takes a special brush to do it right. Why not just cut the damper and be done with it...its easy to do...if you ever want to use the FP as an open FP again (you won't though) you can just install a top damper.
I cut my damper out. I have a double sided fireplace with an insert stuck in one side.. if you ever want to reinstall the damper it’ll give you an excuse to learn to weld if you don’t already know how... I agree with the comment about chimney cleaning.
I saw on the net years ago where an installer took a flex liner and ovalized the bottom foot or so by a half inch or so to make it through the damper opening. Once through, it was rounded out again to fit the appliance connector. Minimal distortion. Some dampers are cast iron and welding it back can be difficult. Just another option that may need some exploring. I agree that round is a good way to go as smoke rises in a helix path.
I agree with any and all that recommended you go round and cut the existing damper. It is a bit of a dirty job but not too hard. I cut mine with an angle grinder and cut off wheel. It is a breeze to clean, of course if you are on at least the 3 year plan there is never anything there anyway.
Yup, regular old abrasive cut off wheel for the damper, and $15 diamond blade makes quick work of any brick that need trimmed...but it sounds like you will not need to do much of that with how wide your damper already is...mine was much narrower...maybe 4"...I had to cut some brick out too.