I have a 2 story home with basement and my 2nd floor is not cooling like it did last summer. This summer isn't really
any hotter than last year, but my 2nd floor unit runs a lot during the day, and the thermostats are set to the same
values as last summer.

I have a few thermostats/hygrometers I use around the house and taped them to the return/supplies in the master bedroom
to check the temp difference. When the attic was around 110 on a hot day, the supply was blowing in air at 68-69 and the
return was taking in air at 77. I had a technician come out to inspect and he said the 8-9 degree difference was due to
the heat loss in the runs in the attic. He quoted some degree per foot run loss, but I don't fully buy it. He also said
they shoot for a 10-12 degree diff for 2nd floors and 15-17 diff for 1st floors.

Today, I measured the temp diff around 8am when the attic temp was 74. Supply was 64, return was 69. I have a 2.5 ton
unit for the 2nd floor. I had let the unit run for a half hour to make sure the air was at its coolest.
For the downstairs, I had 57 from the supply, with 73 going in the return. The basement temp was 75, so the ducts for
the 1st floor, which are in the basement, were roughly experiencing the same amount of heat loss as those in the attic
( attic was at 74 ). The 1st floor unit is a 3 ton.

The house is almost 2 years old. The company that did the install performed a flush/recharge on both units for free
since I'm still under warranty, and that didn't help.

So, I experienced a 5 degree diff when the attic temp was at 74. The system was charged to the recommended level. The
technician came out 3 days after he flushed/recharged and checked the system again.

The airflow seems to be fine. Any thoughts ?