5" stove pipe and 7" thimble

[clesnick]

Hi. I have an unused flue in my basement. It was previously for the oil boiler but we have removed the boiler entirely (now have PVC vented gas boiler elsewhere). I had the flue swept and I want to attach a wood stove to the unused flue. The flue is part of a masonry chimney with 8.5" square clay liner up to the top. The thimble for the oil boiler is in the concrete foundation of the house and penetrates into the brick chimney.

The thimble for the oil boiler was 7" and the collar/stove pipe for the wood stove are 5". I am planning to cut a 5" hole in a 7" cap so that I can pass the 5" stove pipe into the unused flue. I attached a diagram that shows what I'm planning.

Questions:

* Is there a better way to insert the 5" stove pipe into the 7" thimble? I couldn't find any adapters that seemed to be a better fit.

* How far past the thimble opening should the stove pipe go? A mason advised running it to the edge of the clay liner, so that's what I'm planning to do. But, just to confirm, does the diagram look reasonable?

Thanks for your help!

 

[DAKSY]

Hi. I have an unused flue in my basement. It was previously for the oil boiler but we have removed the boiler entirely (now have PVC vented gas boiler elsewhere). I had the flue swept and I want to attach a wood stove to the unused flue. The flue is part of a masonry chimney with 8.5" square clay liner up to the top. The thimble for the oil boiler is in the concrete foundation of the house and penetrates into the brick chimney.

The thimble for the oil boiler was 7" and the collar/stove pipe for the wood stove are 5". I am planning to cut a 5" hole in a 7" cap so that I can pass the 5" stove pipe into the unused flue. I attached a diagram that shows what I'm planning.

Questions:

* Is there a better way to insert the 5" stove pipe into the 7" thimble? I couldn't find any adapters that seemed to be a better fit.

* How far past the thimble opening should the stove pipe go? A mason advised running it to the edge of the clay liner, so that's what I'm planning to do. But, just to confirm, does the diagram look reasonable?

Thanks for your help!

View attachment 112559

You should run the connector at least an inch past the terra cotta liner. That way anything that runs out of the connector will stay IN the chimney, & won't run down inside your basement. You should probably cram some rockwool insulation around the 5" pipe within the thimble to kinda stabliize it & maintain a bit of an upwards pitch into the chimney. Then you can finish it off with a trim collar...

 

[mellow]

Is this for a USA install? Both sizes are not normal.

 

[DAKSY]

The 7" thimble from an oil burner isn't that wierd, who knows how old it is...
Masons built whatever they needed back in the day.
Jotul sells at least two stoves in the USA with 5" outlets on them.
The 602 & the 118 come to mind...

 

[Bluerubi]

I have a 7" thimble in my basement as well. Built in NH in 2005. Have been told since the beginning it was an odd size, so not sure why it was selected.

 

[clesnick]

Is this for a USA install? Both sizes are not normal.

It is for a US installation. The stove is a Waterford with a 5" collar and the oil boiler was installed in the 1950's and had a 7" connection to the chimney. Do you think the sizes will cause problems?

 

[DAKSY]

You may have a problem getting the draft to start pulling adequately to keep smoke out of your basement. Your Terra Cotta is almost 4X the cross sectional area of your connector (3.68x actually). Once your get er going you should be fine. You may notice more of an issue in the "shoulder" season...

 

[mellow]

I would run a 5.5" liner down that chimney.