How to Vent Pellet Stove Through Square Masonry Chimney in Basement?

[LouisB]

Hello, after talking to a handful of experts in the area and doing homework here on the forums we've decided to buy a pellet stove from a local dealer (Regency GF40-2) and have a separate company help us with the install. The installers are going to inspect the existing chimney, and if it checks out ok we don't plan on putting in a liner.

Question is (assuming no liner is needed) how does one convert from a 3" or 4" PL Vent to a 8" Terracotta chimney?

I gather some sort of special "Stove Pipe Adapter" or "Chimney Pipe Adapter" is needed but I'm not sure how.

Picture of Wall before drywall:

Closeup:

Size:

 

[EbS-P]

I’m not an expert but I think any chimney needs
To be installed to code. Again no expert here but the framing is way to close to the clay. Did you install the clay?

 

[LouisB]

I’m not an expert but I think any chimney needs
To be installed to code. Again no expert here but the framing is way to close to the clay. Did you install the clay?

I tend to agree and we will definitely have a very thorough review of clearances to combustible materials before anything is fired up. The clay is original to the house.

 

[EbS-P]

Code probably says 18” from clay to combustibles. Once that’s sorted. I would drop a flexible pellet liner down but you need enough room to get a T on it. Is there a clean out on that flue?

What does the stove manual say about venting into a clay flue?

 

[LouisB]

Code probably says 18” from clay to combustibles. Once that’s sorted. I would drop a flexible pellet liner down but you need enough room to get a T on it. Is there a clean out on that flue?

What does the stove manual say about venting into a clay flue?

Good questions. The manual says:

"You can vent the stove through an exterior wall behind the unit or connect it to an existing
masonry or metal wood stove chimney (must be lined if the chimney is over 6” (15 cm) diameter,
or over 28 inches² (180 cm²) cross sectional area)"

Darn, looks like I may have to get a liner after all because the flue is definitely more than 28²

p.s. I don't believe the flue has a clean out

 

[EbS-P]

If this isn’t a basement it might be easier but more expensive not to use the existing chimney. But pellet vent is cheaper that wood stove venting

 

[LouisB]

If this isn’t a basement it might be easier but more expensive not to use the existing chimney. But pellet vent is cheaper that wood stove venting

Yes I see your point. Less risky to put in an entirely new chimney vent. You guessed correctly though, this is a basement 👍

p.s. updated title of the thread to indicate basement

 

[72Rover]

Good questions. The manual says:

"You can vent the stove through an exterior wall behind the unit or connect it to an existing
masonry or metal wood stove chimney (must be lined if the chimney is over 6” (15 cm) diameter,
or over 28 inches² (180 cm²) cross sectional area)"

Darn, looks like I may have to get a liner after all because the flue is definitely more than 28²

p.s. I don't believe the flue has a clean out

The idea is that you *don't* want the smoke to slow down. When the smoke slows down, it cools and when it cools, it deposits creosote. You want the smoke path to be as straight and hot as possible 'til it vents out the chimney. It this situation, it would be turning and slowing down at the same time.

Now pellets will reduce the possibility of creosote - but not eliminate it - when compared to ordinary firewood. When I installed my Vermont Castings "Resolute" 42 years ago in my fireplace, it was simply vented straight up into a tile-lined chimney (8x16" IIRC). A 1/4" steel plate closed off the damper, with a single 6" by 3' steel pipe shoved up the stack. Alarming deposits of creosote at the top. From then on, it was steel pipe all the way out the top. The stove has an amazing draft - and under certain climactic conditions, it might be too much....

 

[Mt Bob]

I would bet double wall pellet pipe slid through your liner section, with a "pie plate" round trim installed on the drywall yet to be put up would meet all codes. However, an inspector may want a wood stove thimble where that section of liner is right now. Still no big deal.
Some stoves do just fine vented into something that small,8" square, without a liner, some do not, and you would need a liner inside the chimney.. Without a liner, you just use a section of pipe that goes into the chimney a few inches.
You would probably have to call the manufacturer about using a liner. I feel a liner is preferable, but not always necessary.

 

[bholler]

No that is not useable as is. And no you can't just run pipe through it with a pie plate. That thimble needs 12" of solid masonry on all sides of it. And then yes I would recommend a liner. Some pellet stoves do work ok vented into an 8x8 clay liner. But you would need a sealed positive connection to the chimney

 

[Mt Bob]

No that is not useable as is. And no you can't just run pipe through it with a pie plate. That thimble needs 12" of solid masonry on all sides of it. And then yes I would recommend a liner. Some pellet stoves do work ok vented into an 8x8 clay liner. But you would need a sealed positive connection to the chimney

Good info.
Or, frame out a 15" square opening, put in a insu-flu, then run pellet pipe through it.

 

[bholler]

Good info.
Or, frame out a 15" square opening, put in a insu-flu, then run pellet pipe through it.
View attachment 300285

Yes an insulated thimble works well also we do allot of them. But we use the ventis one. The insu-flu is a real pita to install

 

[LouisB]

@Mt Bob, @bholler thanks for the parts & framing recommendations, I'll definitely look into those!

Link I found to the INSUL-FLUE

 

[LouisB]

BTW - I'm looking at a quote I got from the local fireplace shop who were physically here to look at my situation and for a thimble they have "(broken link removed)." The quote assumes a liner would be used. These are the same people that insisted they do everything "by the book" and didn't want to even discuss a non-liner install.

 

[Mt Bob]

BTW - I'm looking at a quote I got from the local fireplace shop who were physically here to look at my situation and for a thimble they have "(broken link removed)." The quote assumes a liner would be used. These are the same people that insisted they do everything "by the book" and didn't want to even discuss a non-liner install.

Chimney guys are usually the best source of knowledge. The one they want to use--how would you service it in the future?? Mine is similar to yours, years ago I build a block chimney, exterior, clay liner, for a wood stove. Outside wall right up against the chimney, and is wood. Cut out the required amount for space, used a insulated thimble. All to code. When switched to pellet, slid pellet pipe through existing thimble. All meets code.