I have a sled standing wood stove right now that I don’t care for and thinking about changing to a pellet stove. Can somebody please tell me why I can’t use my existing wood stove chimney pipe with a pellet stove. Duravent makes an adapter to go from a 3inch to 6 or 8” so the piping can be done. The existing is a class A double wall pipe that is 8”. I think the company selling me the stove just wants the money but maybe I am missing something. Any help is very much appreciated!!