You won't believe this one. A 1850 sq ft house on a slab. House is 14 months old and customer cannot get summer temp in house under 79 degrees inside. Unit has been looked at several times and all is well they say. Customer might have found the problem. The dust pattern on his filter is about 8x15. Who ever installed this unit did not cut the hole big enough.
How much CFM is the unit producing with that small of a hole. How large should the hole have been? Customer has a 3 ton A/C.