@Brian1946, I just hung a thermometer over the front of the vent and left it there for an hour… analogous to when the repair guy points an infrared thermometer at the vent.
@Judi, a typical residential A/C system always just blows the coldest it can. When the temperature at the thermostat has reached the set point, it turns off. It’s all or nothing. It doesn’t matter if the thermostat is set at 60° or 75°... it blows the same cold-as-it-can air. That’s why your a/c actually shuts off… else it’d just run continuously at 72° or whatever your set temp is, like in your car (where you can mix hot/cold air). Fyi: during the day, I have the downstairs set at 78° and upstairs at 81°. At night, I shoot for around 74°.
@thorninmud, was afraid of that… but was also hopeful that the ducting in the attic, once cooled after the A/C had run long enough, wouldn’t be that big of an impact.
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30–40° temperature differentials are hell on my electricity bill.