I recently revovated an old house with all new ductwork, furnace (GMV95/ GCV9 Two-Stage, Variable-Speed Gas Furnace), and spray foam. I decided to keep the old condensing unit since I had replaced the coil 6 months prior to making the decision to completely revovate the house. The condensor is an old Carrier 38CKC048360 (I tried posting a pic with product information I think it's a 4ton 10 seer unit, but I'm not too sure how to tell). Anyway, I think it's starting to give out, and I want to replace the unit rather than troubleshoot the capacitor, fan motor, etc. I am having to push start the fan now whenever we turn the air on. The current unit has never performed well relative to the furnace, and I've gotten an offer from my HVAC guy to install a slightly used 4 ton 12 seer American Standard unit for $800. My HVAC guy installed everything that I have now, and I trust him as much as anyone that I've ever done business with. He works in the commercial business, but does residential on the side over weekends, etc. My only concern is, should I try and find a different replacement in order to achieve maximum performance? My house is 3100 sf with high ceilings 2 zones (upstairs and down), and even when the existing unit was running great, it was hard to keep the house at 75 degrees when the outside temp was in the upper 90s.
I haven't discussed asked for a cost on installing something different, but I'm sure he would do it. I just need to know what is the best move that I can make at this point in terms of performance, effieciency, and compatibility? Would the deal for $800 for a slightly used American Standard unit installed be a good deal assuming that he is willing to back it for a couple of years?
Thanks for taking the time to help with my situation, and please let me know if I've left out any pertinent information.