"JoeSpareBedroom" wrote in message
...
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?

Yes. In most cases, the design is for a 20 degree temperature drop fron the
outside temperature. If that was the case, you should be good to about 72
degrees. OTOH, it may have been designed for a 15 degree drop.


Or, does this mean that the previous owners didn't
have the right unit installed?

Depends on your definition of "right". There may be some problem that is
starting to show, such as a refrigerant leak. filter getting blocked, dirty
condenser coil, etc. To go from a 2 hour cycle to running near constant for
only 1 degree does not seem right. It may pay you to have a tech check it
out now under heavier loads.