Looking at replacing two, builder grade, 18 year old heat/air split systems in suburban Atlanta.
Have received several quotes. Like the Rheem/Rudd systems. Proposals are for Modulating furnace in lower unit (basement/1st floor) and 80% 2-stage variable speed unit for attic (second floor).
Contractors do not recommend 90+ units in unconditioned space. Said the flue gas could freeze up and cause the system to shutdown on the coldest days of the year.
How realistic is this problem? The payback for a 94% unit is only about two years based on the quotes in front of me. Plus, it seems the Modulating furnace is newer technology.