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Homeowner Q: typical cooling differential?

When designing a system, what is the typical temperature delta (outside vs. inside) that is regarded as normal if the system is operating normally?

ie: when its 95 outside, and you have the thermostat set at 72 permanently, what would you normally expect the inside to be?

I know its whatever the system was designed for after a heat load calc, but what is the range of "normal" in designs.


  • Gordy
    Gordy Member Posts: 9,530
    right design

    If it is designed right then 72* is what you would expect.
  • TonyS
    TonyS Member Posts: 849
    In eastern PA

    I design for 20 degrees, otherwise an oversized unit wont run long enough to dehumidify.

    With the inverter mini splits you can go more.

    Central air with an ECM blower and a humidistat can also be a little larger because the airflow over the coil can be slowed down until the humidistat is satisfied.

    I would imagine in areas with low RH the unit is never oversized, just faster.
  • Techman
    Techman Member Posts: 2,144
    another opinion

    Since I'm just a repair guy I don't have to be correct.I thought the design TD used to be 20* but now it is recommended to be 15* Lets hear from The Professor or a design engineer.
  • TonyS
    TonyS Member Posts: 849
    Thats what I heard

    15 degrees is what is recomended...that being said, I am sure who recommended that doesn't have to answer the phone and listen to customers complain why they can only cool their house to 80 degrees.
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