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.