At night the outlet registers blow air between 60 - 64 degrees, the return register air leaves at about 76. During the day the outlets blow only 72 - 75 degrees, with the air exiting into the return register at about 78. The overall upstairs of the house is approximately 50 x 25 and I have a 3 ton unit. The evaporator coil and condenser were replaced last fall. By my calculations the unit requires 1200cfm on the returns, and I have 4 return registers in different rooms running 6" return flex duct. From some web sites it sounds like that is not sufficient to achieve the 1200cfm requirements of a 3 ton system, but the flow into the rooms doesn't seem bad. Would inadequate return flow cause the symptom of increased temperature of the air coming from the outlets during the day? Everything seems insulated in the attic, what could be causing the attic temperature to have such a profound effect on the temperature of the outlet airflow into the rooms?
Many thanks for any advice,