I have 90 LG ptacs in our hotel. These were manufactured with aluminum condenser coils which developed leaks. LG has replaced those coils, copper, but now our warranty has run out and we have about 50 of the aluminum variety. Best price I could find replacement coils is $ and I'm thinking that maybe instead charging a couple and see how long they last. Possibly I can find the leak if it's where the aluminum and copper join which I'm told is likely. At any rate, what drop in replacement can I use for these since they currently use R22? Any advice will be greatly appreciated.