Chimney Help for Noob

Guys looking for some help with installing a MKIII into an existing fireplace. The current masonry tile lined flue is 7x10. The flue on the MKIII as you know is 6". How do I go about making the transition from the stove pipe to the existing fire box? The is an existing 26" wide damper in the fireplace. Can I just vent the stove directly into the existing flue by extending a 6" stove pipe up into the existing flue for 3-4'? would I "seal" the remaning 20" of opening with rock wool or something? Any insight would be helpful. Thank you.

Hi pal I very recently blocked my 30" wide damper opening in my fireplace for the same reason. I cut 2 pieces of cement board approx 8" x 12" and put them on top of the damper opening. I put a couple bricks on top of the cement board to hold it in place as I sealed around the edges with fire rated mortar. I also have some boiler insulation to jam around the black ovalized black pipe that goes into the clay lined chimney, easy peezy

Qtown1835 wrote:Can I just vent the stove directly into the existing flue by extending a 6" stove pipe up into the existing flue for 3-4'? would I "seal" the remaning 20" of opening with rock wool or something? Any insight would be helpful.

That should work or you can get more elaborate as michaelanthony did.

would there be any reason that my 7x10" tile flue would be too large? Or create some unwanted issues? So I guess if I block off the large opening as shown and then extend some singlewall pipe into the existing flue, enough to get past the smoke chamber I should be in business. I should probably include a tee for a baro damper as well.

Qtown1835 wrote:would there be any reason that my 7x10" tile flue would be too large? Or create some unwanted issues? So I guess if I block off the large opening as shown and then extend some singlewall pipe into the existing flue, enough to get past the smoke chamber I should be in business. I should probably include a tee for a baro damper as well.

I used my Vigilant in the fireplace with the cement board blocking the fireplace opening only and single wall pipe into the unblocked damper. It worked well but looked like crap. I had some fiberglass insulation and put that above the damper on each side of the pipe to simply fill the void above the damper.
Pardon the foot, post surgery last February.
A "T" is always an excellent option for a baro and cleaning the pipe without shutting down.

Qtown1835 wrote:would there be any reason that my 7x10" tile flue would be too large? Or create some unwanted issues? So I guess if I block off the large opening as shown and then extend some singlewall pipe into the existing flue, enough to get past the smoke chamber I should be in business. I should probably include a tee for a baro damper as well.

Yes it is larger than ideal. Better if it is all inside the house rather than outside wall. Trying will tell you better than anything. Having a manometer hooked up will give you draft pressure readings and help with any decisions about dampers or other measures. Hook it up as simply as possible to try. Unfaced fiberglass is OK too to seal chimney.

Welcome to the FORUM QT--Indeed it will work--many pro's & cons on the baro--personally I just use an MPD--by the way Quakertown -- finish fillin out your profile--I promise, nobody'll steal ya & it'll give us an idea what ya got stove wise without having to back track:)

Qtown1835 wrote:would there be any reason that my 7x10" tile flue would be too large? Or create some unwanted issues? So I guess if I block off the large opening as shown and then extend some singlewall pipe into the existing flue, enough to get past the smoke chamber I should be in business. I should probably include a tee for a baro damper as well.

Thanks for the welcome and the advise. I updated my profile too. I wasn't trying to be anti social, promise.

freetown fred wrote:Welcome to the FORUM QT--Indeed it will work--many pro's & cons on the baro--personally I just use an MPD--by the way Quakertown -- finish fillin out your profile--I promise, nobody'll steal ya & it'll give us an idea what ya got stove wise without having to back track:)

Qtown1835 wrote:would there be any reason that my 7x10" tile flue would be too large? Or create some unwanted issues? So I guess if I block off the large opening as shown and then extend some singlewall pipe into the existing flue, enough to get past the smoke chamber I should be in business. I should probably include a tee for a baro damper as well.

Qtown1835 wrote:would there be any reason that my 7x10" tile flue would be too large? Or create some unwanted issues? So I guess if I block off the large opening as shown and then extend some singlewall pipe into the existing flue, enough to get past the smoke chamber I should be in business. I should probably include a tee for a baro damper as well.

Yes you should be fine but a manometer tells the truth and can help diagnose fly ash build up as he draft will slowly decrease. My clay pipe is the same size as yours, it's also in the middle of my house and 20 ft high.....and not far from a mile high mountain, (mt. katahdin), so you see every install has variables both plus and minus.

Unfaced spun fiberglass insulation is common, but our Northern Brothers use a different house/building insulation.
They use Roxul, it is unfaced, and I am starting to see it available here in the States.
Would be a excellent product for fire blocking. Check it out at both the "big box" stores.

That is exactly what I am planning on usung. I have about 3/4 of bag left over from another project. I will be working on building my coal bin today. Im way late to the game...

McGiever wrote:Unfaced spun fiberglass insulation is common, but our Northern Brothers use a different house/building insulation.
They use Roxul, it is unfaced, and I am starting to see it available here in the States.
Would be a excellent product for fire blocking. Check it out at both the "big box" stores.

Qtown1835 wrote:Can I just vent the stove directly into the existing flue by extending a 6" stove pipe up into the existing flue for 3-4'? would I "seal" the remaning 20" of opening with rock wool or something? Any insight would be helpful. Thank you.

Yes, that's what we did and it worked well. Lay the pipe out of the floor, screw it together and then "field modify" it by squishing it thin enough to fit through the damper. Take the pipe apart and feed it up the chimney one pipe section at a time, taking care to fasten each section with 3 screws. We then filled in the damper with "rockwool" and called it done. The stove has a good draft and yet we didn't permanently change the chimney for the next owners.

The only thing I'm doing different this year is I made a "casing" for the "rockwool" out of chicken wire so I could shape it easier and it would stay in place better. Good luck, Lisa