Chimney flue back drafting down the adjacent flue. Chimney extension?

[Deere-nh]

Hello all, I have a three flue chimney. All three flues are at the same height. I use the middle flue the most and oncassion use the flue to the right as well. I have noticed when I use the middle flue I will get a back draft on the flue to the right.

I am looking to get a chimney top extension kit. Any recommendations on how they work? And if this would fix the problem? Thoughts on heights as well? I was goimg to go with 18" one. I don't live in a windy environment but was concerned if the wind would blow it over.

 

[begreen]

It's a common problem. The smoke is back siphoning down into the lower floor chimney. An extension on the main floor flue will help.

 

[Deere-nh]

It's a common problem. The smoke is back siphoning down into the lower floor chimney. An extension on the main floor flue will help.

Would you recommend a 18" or 24" extension?

 

[begreen]

18" should suffice. That uninsulated section will cool down the flue gases quickly.

 

[Deere-nh]

18" should suffice. That uninsulated section will cool down the flue gases quickly.

Does this pipe need to be insulated? I was trying to see if they made a terra cotta top plate that went to SS liner to a class A stove pipe but had no luck.

 

[begreen]

Anchor plates for conversion to class A exist in several brand lines and some have support systems for the liner available.

 

[Deere-nh]

Anchor plates for conversion to class A exist in several brand lines and some have support systems for the liner available.

Does the extension need to be insulated or will I be fine without?

 

[begreen]

Does the extension need to be insulated or will I be fine without?

That depends on the setup and stove and operator. Do you know what the normal flue temps are?

 

[Deere-nh]

That depends on the setup and stove and operator. Do you know what the normal flue temps are.

I dont. The woodstove is in a fireplace and am not able to get the thermometer at proper height. The stove temp is usually around 400 to 600.

 

[begreen]

How tall is the liner and is it insulated? What stove is this for?

 

[Deere-nh]

How tall is the liner and is it insulated? What stove is this for?

The liner is 6" SS 20'. It is not insulated however, it is in a masonry chimney, inside a 12" SS liner. The stove is a vermont casting aspen c3.

 

[begreen]

The liner should be insulated, there's plenty of room and a lot of heat loss in 20' of uninsulated liner in a cold exterior chimney. If the brick chimney doesn't have at least 1" clearance from combustibles then insulation is required. It can be retrofitted by pulling the liner out.