I've just re-read this thread. Frankly, aside from continuing to push this matter up the ladder at Carrier, your best bet might be just what LdiJ suggested. A portable air conditioner for the affected room for the four months of the year that you need it. It's going to cost you thousands (if not tens-of-thousands) of dollars to pursue this in court, in addition to the cost of the new system that you will have to shoulder, versus $500-$1,000 and a couple dozen nights a year of using the portable unit.