Ovalizing a liner?

[TMonter]

I'm helping a neighbor of mine I cut wood with install a new stove and we found out his masonry fireplace has a 4.5" x 20 inch opening for the damper into the flue.

He had wanted to install rigid pipe but I think I've convinced him his best bet is a flexible liner like mine. I don't have any experience ovalizing a liner to go through the damper, so what is the rule of thumb for doing this?

Also once the liner is ovalized and through the damper section, what's the best way to make it round again for hookup to the stove?

 

[MrGriz]

When I did mine, I didnn't have to ovalize it quite that much (opening was just over 5"). I just used a scrap piece of 2 x 6 across the end of the pipe and leaned on it (one advantage of carrying around the 12 pack abs instead of the 6).

I'm trying to remember how I re-rounded the liner for the connection. I know I tried using a band clamp. It was either that or just good old fashioned muscle power, now I can't remember.

 

[Corey]

My .02 - That is going to be a pretty good "crush" going 6" dia > 4.5" oval. You would probably be far ahead - for ease of installation, cleaning, and just peace-of-mind that you haven't burst any of the seams in the liner - to go ahead and chuck up a metal / masonry abrasive disk in your grinder or circular saw and take out the damper and possibly a brick or two on the smoke shelf.

(Been there, done that)

Corey

 

[jjbaer]

My .02 - That is going to be a pretty good "crush" going 6" dia > 4.5" oval. You would probably be far ahead - for ease of installation, cleaning, and just peace-of-mind that you haven't burst any of the seams in the liner - to go ahead and chuck up a metal / masonry abrasive disk in your grinder or circular saw and take out the damper and possibly a brick or two on the smoke shelf.

(Been there, done that)

Corey

Few suggestions: 1) on mine, I did as the the previous poster has suggested and borrowed a grinder and grinding wheel and sliced out parts of cast iron or steel from the damper assembly. I also had to remove a few firebricks, then I (ever so slightly) "ovalized the liner and it passed through. Then I cut some of the bricks down a bit and re-cemented them back into place. ALWAYS wear goggles, gloves and hearing protection when you do this as you're in a confined space (hearth) and thing fly off the grinding wheel. 2) you could purchase a short oval extension that runs from the stove and passes through the damper area which then connects to an oval-ended liner but it can be hard to connect them and you'd be choking down the 6" quite a bit to 4.5" for it to pass. My liner is 1-piece and runs from the top to the stove connector, passing through the enlarged area I made in the damper.

 

[philaphire]

I considered ovalizing but decided to cut the damper and was pretty anxious about it. Turns out, it was pretty easy. My damper is 1/4" steel and there was enough room between it and the masonry for a sawzall to do the trick. I would recommend getting a good look at the damper and what it would entail to cut it out and then cost/benefit analyze cutting the damper vs. ovalizing and re-rounding the liner. You never know - it could end up being a much easier job than you think!

 

[Mike Wilson]

When I did mine I had it sandwiched between two 2x10s, and it came out fine. I re-rounded the stove end with a C-clamp and some smaller wood. I needed to get to a 5" opening, and it works fine.

-- Mike

 

[theheatelement]

One gentleman that sells our liner on ebay actually has us ovalize the liner for him or at least the last 5 feet.... we then have a connector to change it from oval back to round.... it has worked perfect for us so far..