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Delta Temp from AC Vents

If the air going in to the space (or more accurately, what is coming off the coil) is in the 58-59 degree range, saturated, that is the lowest dew point you can maintain in the space.

55F is a key temperature because it mirrors the same space dew point of a room at 75 F and 50% RH.

Long term even if running flat out at those conditions, you are not dehumidifying nearly enough, IMHO.


  • Steve Garson_5
    Steve Garson_5 Member Posts: 11
    Delta Temp from AC Vents

    I suspect everything is OK, but had to ask:

    Outside temp is 95*
    Indoor temp is 76*
    The air temp from my vents is 59*
    Compressor is on 100%

    Does the fact that the cooled air is 59* indicate that the system is working OK and the issue might simply be that there aren't enough BTU for this kind of heat? Should I not use the afternoon setback (78*) since it is so hard to cool down afterward?

  • John Mills_5
    John Mills_5 Member Posts: 951

    Don't use much of a setback in a heatwave. A/Cs are good maintainers but under max conditions, unless it is way oversized it will not drop the temp. If we get 95°, I hit HOLD!

    With good airflow, temp drop over the coil should be 15-20° depending upon humidity. If you are reading at registers you reflect any duct heat gain so could be lower. Sounds like you are doing OK.
  • mtfallsmikey
    mtfallsmikey Member Posts: 765
    Now it is considered wasteful

    But I used to go 1/2 ton oversize when selling A/C or heat pump systems. And calculated based on 75 deg. inside temp at 100 deg. outside temp. Kept the complaints down, but not too much oversizing as to cause short-cycling or lack of dehumdification. Keep the blinds drawn, put the fan in the "on" or manual mode so it runs constantly, have the system checked. Depending on how the whole system was sized and installed, this may be the best it can do.
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