Electric Furnaces System Selection :

• Is it important that my ductwork match up exactly to my new furnace?                         Back

  Not at all. Unless the replacement furnace is identical in size to the old furnace (very unlikely) there will always be some duct modifications necessary to complete the job. Furnace installers expect this and are prepared to make changes as needed.
  
  If your existing furnace configuration or location is changing, prepare in advance to ensure that you select the right furnace.