My daughter had trouble with her central A/C during the recent hot spell. Daily high temps above 100, possibly as high as 110. Basically, could not get the house below about 85. It seemed to me the compressor was shutting down for periods of time. ( The condensor fan stayed on, and the inside blower fan stayed on ). The air would be recirculating, but you could feel at the duct it was just recirc, not cooled. Then after maybe an hour, the compressor would kick in again. They contacted their A/C contractor recently and he said " nobody's system works when it's 110". Is that a blow-off, or a reasonably reply. Since I already have a long winded post going here, let me elaborate on the system: 9 months ago, inconjunction with a 500 sq.ft. room addition, they had this contractor install a new horizontal Trane XL80 gas furnace in the attic, new coil, but kept the 3 ton Heil condensor, which is only about 6 years old. He said the system was big enough for the new sq.ft. With my just dangerous enough knowledge, I am suspecting a return air problem. Used to be a direct input into the botton of the old vertical furnace, through 2 large grills into the closet. Now, return air is a single 20X20 grill, connected to the unit with about 20 feet of 16" ID flex insulated duct. Could this be a problem, or is there a more basic issue?