Best approach to hearth mounting with a small flue

[deese]

Good afternoon all. I've been lurking for the past few weeks doing research, finally posting as we get to the point of choosing a stove and an installer. I want to make sure that we responsibly balance safety, stove performance, and overall cost of the installation. (While I'd like to save money, the other two are more important priorities 🙃)

My house in the Boston area is a 1937 2-story Cape-style, ~1500 sqft. We have a central brick chimney (32" square on the outside) with 3 terracotta lined flues, each 6 3/4" square (size of the opening). The flues service 2 fireplaces (1st fl living room, and finished basement) and our gas boiler.

We want to add a fireplace insert or wood stove to the living room fireplace for better efficiency. We're leaning towards a wood stove for aesthetic reasons, specifically the new Hearthstone Lincoln. It's a small stove (15K-20K BTU), but we don't need much because its in a small room (300sqft) and we don't have great air circulation or plans to improve it.

The only wrinkle in our installation plan is that the stove wants a 6" insulated SS liner, which will not fit in the existing lined flue. One installer has suggested breaking out all the terracotta tile to make space for a liner, and another has suggested running a smaller diameter liner (I think it would have to be pretty darn small to fit!). The stove manual says that using an existing lined flue is ok with a max size of 8" square, so I think that running stovepipe to the existing flue would be a third option -- but one of the installers was against this.

What do you think is the best approach for me?

I've attached pictures of the flues exiting the top of the chimney, the firebox, and the hearth. While it's not exactly relevant to my question, I'll include firebox and hearth dimensions below. If you think I'm picking the wrong stove, or I should go with an insert, feel free to chime in.

Thanks 🙏

Firebox opening: 34 1/4" wide by 27 1/2" high
Firebox at back: 24" wide. 25" high at 17" of depth.

Hearth: 18" in front of firebox, 7" past sides of firebox
Distance to combustibles: 6" to trim at sides and top, 50" from floor to mantle

 

[deese]

I forgot to mention that the chimney height is around 22'.

 

[bholler]

I would break out the clay and do it right