re: AC question.

quote:

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There's about a 10 or 11 degree difference. Air blowing out the vent is around 66 degrees. Air being pulled into the return is about 76-77 ish.

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That's low, but how are you measuring? For supply registers, one valid way is to stick the probe end of an instant read cooking thermometer into the duct and wait a couple minutes. It's normally possible to jam the LCD end into the register fins and leave it there. OTOH, pointing an IR thermometer at the register is not valid.

The time of day can also affect the measurement. You'll lose split during the heat of the day if your ducts are in a hot attic and aren't incredibly well-insulated; the longer the run, the greater the heat infiltration.