Help with exhaust

[Stumppy]

So just bought the house and making sure everything is good with the pellet stove and have a question on how they vented this thing. They ran a stainless vent pipe through the old chimney but they cut the chimney off in the attic and then attached to an exhaust pipe through the roof. Is this even safe? How would I go about fixing it?

 

[tbear853]

Are you sure the smaller pipe is just attabched to the bigger one?

My thoughts ... that pellet vent pipe is the small one, it has a stailess steel inner pipe if it is pellet pipe, and not just gas vent. It has a nearly 3/8" air space to the outer galvanized shell you see. Being in a flue built for fires, I wouldn't worry as the outer pellet vent wall gets hot, but not super hot. Then you have a flue liner which itself has a air space to an outer wall, then the flue.

IF the pellet vent is just attached to a larger flue, I'd add pellet vent the whole way, even if inside the flue liner. Pellet stoves have fan driven exhaust, they have a pressure. Regular flue pipes use convection, they have a draw of thier own.

 

[Stumppy]

Are you sure the smaller pipe is just attabched to the bigger one?

My thoughts ... that pellet vent pipe is the small one, it has a stailess steel inner pipe if it is pellet pipe, and not just gas vent. It has a nearly 3/8" air space to the outer galvanized shell you see. Being in a flue built for fires, I wouldn't worry as the outer pellet vent wall gets hot, but not super hot. Then you have a flue liner which itself has a air space to an outer wall, then the flue.

IF the pellet vent is just attached to a larger flue, I'd add pellet vent the whole way, even if inside the flue liner. Pellet stoves have fan driven exhaust, they have a pressure. Regular flue pipes use convection, they have a draw of thier own.

Would I need to worry about the insert getting to hot in the old manufactured stove area since there is no longer the air cooled chimney drawing air down to the fireplace?

 

[tbear853]

I know that I have never suffered a burn touching pellet vent, but then I don't touch it for long. I've seen stove pipe burns though. In your case, the existing flue liner will never get near as hot as it would with a wood fire and no pellet flue. I would make sure the pellet vent is continuous with no leaks, but the older larger flu liner can only provide more insulation. With a pellet stove, a fan pushes exhaust gasses but it's still best to have a "rise" to help keep that hot gasses moving, and that flue liner will not hinder that action at all.

I stressed pellet vent. It looks just like gas vent, same outer jacket ... but gas vent uses aluminum inside liner and pellet gasses will eat it up fast. Pellet vent uses a stainless steel inside liner, it will last. Gas vent is cheap but dangerous to use for pellet stoves. The sections will seal as they are twisted into each other, but many guys add a outer seal of RTV, etc. I use RTV at the stove connection in my house, but not outside.

 

[Stumppy]

The inside of that exhaust pipe looks just like the outside. Not knowing how old this is how do I determine if it’s the correct pipe?

 

[tbear853]

Hard to say looking at the picture, looks almost unused though, I don't see expected black pellet soot.

Maybe I am seeing soot just turned white by the LED light?

Gas vent is aluminum lined, pellet stove vent is stainless steel lined. It'll get black from soot, but a wipe with a old rag and a touch of brake kleen spray will remove the black and reveal shiny stainless steel if pellet vent. My purchases have had labeling on the outside near the joints too, it stays on usually as it's printed on a foil label.

Try cleaning a first inch or so with a wrag wrapped around fingers and some sort of degreaser or 409 or etc. Stainless steel will shine, alumium will be dull.

What is the tape wrapped around in your pictures.

Did the house have a pellet stove already? Pellet vent will often cost $11-$15 or more a foot now, if using 3" ... that's inside the inner liner diameter.
If I was in doubt, I likely would replac e the pellet flu, they even make flexible sections as I recall, but I'd keep the big fire flue liner unless it just doesn't allow me to replace the smaller pellet flu?

 

[Stumppy]

Yeah it’s actually pellet pipe that they have the flexible stainless steel vent attached to. This is how the previous owners ran and setup the pellet stove that is currently in the house.

The tape is just high temp tape they put at the homemade coupler. They screwed the flexible vent to the rigid pipe and then siliconed it to seal it.

I did find some of that old preway pipe that I could put the old chimney back up through the roof which I’m debating on doing or just running rigid pellet pipe all the way down and calling it a day. I just don’t like the heat coming off the pipe going up into the attic but I don’t think that will be a huge deal.