Well, the saga continues....

So that is probably a little better than 8x10 ID...or ~80 sq inches...your new stove calls for ~28 (6" flue)
This oversized and tall! masonry flue explains why you see erratic draft...the height gives you excessive draft when the flue is hot, but then as the stove is turned down, or the fire burns out, the oversize masonry acts like a heat sink and cools quickly...low draft.
Dropping a stainless liner down that chimney would solve those issues...especially if you have room to put a wrap of insulation on it...which is likely needed to meet current code anyways...but even just a bare liner would perform better than what you have now.
A side benefit of a liner (especially insulated) is that since they stay hot they also stay cleaner.
And yes, a key damper would be a good idea...it would certainly be needed with a lined chimney of that height!

 

Right on!

Also.... Don't fear using the Sooteater often until you get this stove figured out. Your masonry is way oversize for the stove design as noted. I would expect potential buildup above and beyond what you had with your pre EPA stove.

 

Tough pills to swallow, but its a direction. I think its going to be a good idea and it would make me a bit more confident I think. I wish I had the budget for it right now. Would you guys recommend dropping a quick single wall until you could put an insulated one in, or just clean it out more and struggle with it?

 

Sounds similar to my setup. 30 foot interior masonry 8x12” clay lined flue, 3 feet of single wall pipe.

 

No offense but only you know the true condition of your masonry chimney. My feelings on 90% of them is that they should be lined with a insulated liner. I have yet to see a completely interior masonry chimney in our part of the country with 2 inch clearance to combustibles as it makes its way up and out of the home (hence the insulated liner requirement). In my old house the wood framing is tight against the masonry chimney from top to bottom! I don't use my masonry chimney. If a masonry chimney is on the outside of the house it needs only 1 inch of clearance to combustibles. In either case a insulated liner is the answer for stove performance and keeping a clean venting system due to much higher flu temps. Food for thought.

 

Yeah, I'd say that's about right. Do you have a liner?

 

Yeah, I've been wondering about that. Thanks.

 

I do know there are clearances in some of the spots, but I doubt that it is that way all the way to the top.

 

Not yet. I’ll have to break the tiles out to get a proper insulated liner in. Could get a non insulated liner in without removing the tiles. That will be a project for after the heating season is over.

moresnow you are correct about knowing if you are code compliant. Unfortunately I know I’m not....

 

Makes me wonder if a flex liner would be the way to go.

Warner , moresnow

 

It is what it is
I have learned a ton from others misfortune on masonry chimney issue's. One of my close friends is a add on furnace guy. Has been for nearly 30 years. In the first 20 years he had the FD out 3 times for chimney fire's. Obviously this gent could not grasp the importance of seasoning his fuel. In the end his place almost burnt down and the masonry chimney was breached in a couple places to extinguish the fire! That chimney is now gone and has been replaced with quality Class A stainless dual wall. Basement up is 35 feet FWIW. Chimney issue fixed. Still twisting his arm on the seasoning issue

 

Flex liner 100%

 

Yes

 

Yeah, now I'm just wondering how to get through January and Feburary.

 

I'm thinking a Tee at the thimble, flex to the top, cap at the top. Sound about right?

 

Just use your soot eater once a month. On a bright sunny day you can put a small mirror in the clean out to monitor what’s happening in there.

 

Yup, you can buy a kit that consists of what you listed cut to length.

 

Chimney Liners, Stove Pipes, and Insulated Chimney Pipes

 

Basically, it wont run the best until I get the liner, but watch it like a hawk. Got it.

 

It’s a double edge sword. A 6 inch liner 30 foot tall could over draft and make the stove hard to control too...