I have a 5 ton 13 SEER Rheem heat pump system with a RPGB-061JAS outdoor unit coupled to a RHQA-2020J airhandler installed horizontally in the crawl space. These are of 1993 vintage. Everything is performing well at the moment and the outdoor unit is in good physical condition with no rust etc.
The air handler however, is rusting out badly and will soon need to be replaced. My question is what is a suitable matching air handler to use? A RBHK-25J18SFE has been suggested. Would this unit provide good performance with the existing outdoor unit?