I have a 14' x 24' living room that currently has 1 heating register and 2 returns. All are supplied with 8" diameter duct. I want to add a second heating register in the room to disperse the heat more evenly. Can I run a new 8" duct, with a damper, back to the main duct without causing any harm to the overall system? Both heating registers will be approximately 15' from the main supply duct. I intend to close the dampers slightly on both ducts after I do this.
Tillio