Fireview installation - 6 inch connector on 8 inch pipe

[Ditchmonkey]

I'm new to all of this and I just discovered that there are two pipe diameters. The stove pipe currently in the house appears to be 8 inch. The Fireview I have on order uses 6 inch. Should I use a 6 inch connector and have the adapter at the current pipe, or use an 8 inch connector and have the adapter down by the stove? I have attached a photo for reference.

I have read that a 6 inch pipe is preferable. Is there anything I should be concerned about with my setup?

 

[Oldman47]

Look at the ratio of the cross-section areas of those pipes. A 6 inch is a bit less than 36 square inches while an 8 inch is proportionally a bit less than 64 square inches. Actual numbers are 28.26 square inches and 50.24 square inches but you don't need to throw in the pi ratio to understand what is happening. With a cross section of nearly double, the flow rate in the 8 inch will be about half as fast as in a 6 inch for the same amount of combustion gasses. That means the draft will be much less in the 8 inch pipe. If you have a very long run of 8 inch, it may work out just fine but if you are anywhere near the desired chimney length the 8 inch will simply not work right. It will give you an anemic draft.

 

[Ditchmonkey]

Maybe I'm wrong about the diameter of the pipe. I measured the 8 inches as the outside diameter, but maybe I needed to measure the inside diameter?

 

[begreen]

Yes, assuming that is class A pipe hanging down there, you measure ID.