On Wed, 22 Jul 2009 17:54:12 -0700 (PDT), Larry The Snake Guy
wrote:

I don't know the answer to your question (that's hapening a lot
today), but how much difference could it make if it sometimes gets to
75 half an hour early? I'd just set it a little early and relax.

I'm sure you could have one built (interface inside and outside
thermometers and the AC to a small computer). It still could be wildly
inaccurate sometimes, because the weather conditions could change
drastically between the time it decides to start and the time you
expect it to be at your set temperature.


I had one that used the rate the temperature changed when it
called for heat or cold to determine needed start time to reach a
given temperature. All you did was set it for the temperatures you
wanted when it then give it a few days to figure it out and it was
good. A sudden big change in outside temperature did fool it a
little, but it was very good. As I recall it was a Honeywell, but
not a current model.