Ovalize a 6" liner or go with a 5.5"?

[JTP11]

Hi,

I'm a long time reader here and certainly have gotten lots of great tips from the hearth community. I've been a wood stove heater most of my life but now in a new home with a fireplace that's a perfect candidate for a Jotul C550 insert. I'm picking it up next weekend and doing the install myself.

The C550 calls for a 6" flue which I have the space in my 23' 8x13 chimney flue pipe, straight up, but I want to use the 1/2" insulation kit with the 316ti liner. They say you must add 1.5" to the liner size for 1/2" insulation. That brings the 6" liner to a 7.5" diameter. Only problem is the I.D. of my 8x13 flue pipe is 7-1/4" and because it's an older chimney there's a little shifting in there.

My question is am I going to be loosing out on efficiency by ovalizing the 6" liner slightly to fit? Or void any warranties? Would it be the same as using a 5.5" liner that I don't have to ovalize? Can a 5.5" liner be used on an insert that's suppose to be a 6"?

I have read about the poured in vermiculite but I don't like it for a few reasons.

Thanks,
JTP

 

[cygnus]

I had the same issue. I chose to ovalize the entire run just a bit and install was a snap. In the end I'm not sure I needed it but the insurance was worth it. Looking back. I have more than enough draft so would have saved some time and effort by going with the 5.5 without sacrificing anything. How tall is the chimney? Mine is 30' so I didn't have an issue. If you have a short chimney then you might be fighting for all the draft you can get and the extra diameter could help.

 

[EatenByLimestone]

I went with the 5.5 on a similar height chimney and have more than enough draft to feed the 30.

Matt

 

[begreen]

You could use a pre-insulated liner like Duraliner. It comes in a variety of configurations that all connect to each other so that you can go rigid and then switch to flex round or flex oval at the damper. It's OD is 6 5/8". http://www.duravent.com/Product.aspx?hProduct=6