We just had a new Trane XR12 installed last week to replace our 18 year old 8 SEER Lennox unit whose fan motor seized. That old unit (prior to the motor problem) used to cool the house well and reached the set point on our digital thermostat (even if is was set <70 during the summer). Here is a day-by-day as to what we've observed.

Thursday 6/23 - Installation Day:
It ran continuously and never reached the set point of 70 (approx. 18hr., got to 76-77). Outside temp. 80.

Friday 6/24:
Had the installer come back out, and we noticed water underneath the unit and they claimed it had likely frozen up. Ok. Turned off the unit, and checked the freon and overall it seemed fine. We had to leave for the weekend, so we turned back on and set at 75. Outside temp 85.

Sat. 6/25 - Sun 6/26: Outside temp >90.

Last night 6/26:
Returned home after weekend and thermostat reading 80. Outside temp. 83. Water again under unit. Turned unit off for 4-6hr. Turned back on for night with a set of 74. Woke up in the morning and it was at 74 - amazing.

Today 6/27:
Temp. set to 73 and it reached 73 by 9:00am. By 12pm, temp outside was 85 and temp inside set to 73. At 3:00pm, thermostat reading 77. Now its reading 78 with unit off. I'm giving it a few hours to settle and will turn back on, set to 75 to see what happens.

It appears the set point is rarely reached with this new system and I am not sure why. Also, there is continually a medium amound of water creeping out from under the unit. The installer is going to come back out Friday to check again, but I am curious to know why a brand new, much more efficient unit is having a hard time bringing the temp down to the set point. Any thoughts?