I currently have a 15 yr old Airquest Central AC: Model NAC060AKA1 Ser.# L021909682 5 Ton in a antiquainted older Space-Pak system that works in conjunction with a boiler system heated home...thus NO duct work and must stay for lack the BIG $ it would cost to R&R the whole system...with that said I have been thinking of picking up a used 2007 TRANE XR-13 5 Ton outdoor unit IN CASE my current Air-Quest expires...now this Trane unit was taken out of service (late 2010) on a R&R to go to newer Refrigerant model and get rebates I guess...the XR-13 is a R22 model which is what I have now...I know the refridgerant is being fased out but I have a new jug of it and wondered if this would be good thinking...I can get it for 300 and it was basically used for three years in a Michigan climate. My big question is: IS IT IMPORTANT for one of these units WHEN REMOVED to be left with Refridgeant IN IT and SEALED up?? or would being left open and dry be a concern if I'm not thinking of putting it in service anytime soon and only if the Air-Quest expires in the future. Appreciate anyones 2 cents on this consderation and ANY advice you might have. As always Thanks also to TOH for the oopurtunity to get the help.