A simple check. An AC system should have about a 20 degree drop across the
evaporator coil. Just measure the temperature difference of the incoming
and outgoing air of the unit. If it is much different something is wrong.
Since it seldom gets above 100 where I live, the delta T maybe less if the
outside air is approaching 120 as it is now in the west. Good to do this
for your furnace too in the winter. That way you can tell if there is a
problem quickly.

"JoeSpareBedroom" wrote in message
...
Just after I moved into my (used) home, I had the AC unit cleaned &
checked over by a company I've been happy with for 22 years. It got a
clean bill of health. This was in September, though, so there was no
really good way to watch it do its thing for any length of time. I'm
finding that on a very hot day (92 outside today), the system runs almost
constantly to keep the house at 76. If I set it at 77, it cycles on for an
hour, off for two, and the house is comfortable. I don't NEED that extra
degree, but I'm still curious: For a given house, and a particular AC
unit, is there usually a point where it just won't do more? Or, does this
mean that the previous owners didn't have the right unit installed?

By the way, the attic is vented & insulated perfectly.