EarthWindandFire wrote:The supply ducts in my house were done very well. However, I have a large return trunk but only one side has a vent which is in my living room. The vent for the other side of the trunk was never hooked up or was covered over. But, regardless, I have no return vents from the second floor.
I have considered using the existing supply ducts and use them instead as return ducts when I remove the existing oil furnace and install a stoker furnace.
Many older houses did have central return systems relying on floor grilles and/or stairs without doors to transfer air down to the first floor. It was fine until the bedroom door was shut at night, but the cold was solved by a big, comfy quilt. (stories from the elders about waking up to ice in the wash bowl have been told.)
Converting excess supply ducts to return is a valid concept, just make sure the remaining ducts have sufficient capacity to handle enough air to heat the spce.