In another thread, Baldloonie wrote:
"Ducts in the attic? That can kill performance right there. If the 1st floor unit has a basement furnace, that helps since the ducts are in a cold basement.
And as the boys say, high SEER especially with too much air, doesn't give the drop of an oldie. "
Does enabling 'high SEER' on an RGFD furnace (RARL a/c) boost airflow above that (400 CFM/T) set on the IFC? System with matching coil is rated at 14.7 SEER.