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I have a Carrier AC in a new home that I don't use often. It is about 90 degrees outside. I use the down button to set temp to 69 degrees. The AC box outside turns on. The vents may blow cold air but it is hard to tell. After I set the temp to 69 degrees the panel goes back to showing 88 degrees. Is the panel behaving as expected? Does unexpected behavior indicate an issue with my AC?

I set AC to this: enter image description here

After a pause, the panel shows this: enter image description here

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  • Does the 88 eventually go down? Commented Jul 28, 2021 at 0:49
  • @ThreePhaseEel so far just down to 86. Its been on about an hour.
    – Bernie2436
    Commented Jul 28, 2021 at 1:15
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    I'd give it overnight, and not play the "shut the AC off overnight" game so much. It sounds like you have a system that's fairly closely matched to your house's load, which is generally intended to be run "set and forget" instead of juggled on and off Commented Jul 28, 2021 at 1:44
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    You are confusing set point (68) which you set it to, with internal temp reading. That's a pretty simple display, most thermostats would show both set point and internal temp. 68 is pretty cool for A/C, I usually run mine at 72-74. But that's a personal preference. Like @ThreePhaseEel you just need to let it run. An A/C system needs to be matched to the house. An oversized A/C might very well cool more quickly but with shorter run times, won't pull the moisture of the air and leave you with a clammy feeling. Commented Jul 28, 2021 at 2:04
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    I suspect you need to hit the "hold" button after setting temp to 69. Commented Jul 28, 2021 at 2:50

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The behavior from your thermostat is normal

Your thermostat has only one spot on its display for temperature readings, but two values (setpoint and actual) it needs to display there. So, it displays the setpoint when you interact with the setpoint (by pushing buttons) but the actual reading when you're not interacting with the thermostat.

As to it taking a while to cool down? This could be due to unseasonably hot weather exceeding the design temperatures of the system significantly, an air leak (such as an open window, a fireplace damper left open in the summer, or simply bad construction detailing somewhere), or a simple factor of having a system that's capacity-matched to load instead of being significantly oversized. Not that having an oversized HVAC system is good, though: HVAC oversizing leads to equipment-wearing short-cycling as well as poor latent heat (aka humidity!) removal as a short-cycled coil never pulls down to the dew point of the incoming air for long enough for condensation to happen.

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