Question about connecting stove to existing flue.

I had my flue cleaned and inspected the other day in the house I bought a few months back. I have a pretty much brand new 8" flue system, I'm looking at an Englander, probably the new cpm model. My question is, do I just need a thimble and reducer to connect the 3" pipe to the existing flue or do I need to run a 3" liner through the entire system? I checked Englander's site, it seems like they don't specify a whole liner, but I've heard other places that you need one. Thanks.

The thimble in 3" should be good...if the chimney is tall you would have to increase to 4" after 12 or 15'..I forget...Give Englander a call...they're more than helpful

If the effective length is over 15 feet you should use 4" pipe. The effective length is calculated by counting each Tee or 90 degree ell as 5 feet, each 45 degree as 3 feet and each vertical foot of piping as 1/2 a foot. Horizontal runs of pipe are counted 1 foot per foot of run.