Hi,I recently had new central ac installed in my home. I live in New Jersey and the summer has been brutal to say the least. I usually keep the thermostat at 79 when the outside temp is 85-95. However when it is 95 degrees or higher outside,I put the set temp to 76-77 degrees. I've noticed that my home will not get any cooler than 79 degrees.Is there something wrong with the unit or could there be an insulation problem etc. I have a 2 story cape cod and the unit is a 2 1/2 ton Rheem. Any insight would be greatly appreciated.

THANKS