I have an old house (1924) that I currently heat with firewood only ( functional but tiresome) I am considering a pellet stove. I would like to vent through a brick fireplace in the living room that I barely use. I lined it years ago with a 6inch liner and clean it accordingly. can I just run the new smaller vent 3 or 4 in from the stove in the chimney without removing the other liner? how does the clean air intake work when using a chimney? Does it run up the chimney as well?