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Short cycle ac concern

3 years ago
last modified: 3 years ago

We had a heil ac installed within the week. House is 2500 square feet with 800 square foot basement. Ac is 3.5 ton. Temps have been mild 75-80. Ac runs about every 10 minutes but for short cycles 5-8 minutes, 3-5 later nite. Hvac installer said that is due to mild Temps and would resolve in warmer weather. Does that sound accurate

Comments (10)

  • 3 years ago

    If house stays comfortable,don't worry bout it.

  • PRO
    3 years ago

    "Hvac installer said that is due to mild Temps and would resolve in warmer weather. Does that sound accurate"

    I'll answer with a qualified "yes." When the difference between outdoor and indoor temperatures is only a couple of degrees there is little cooling load. When the cooling load is low, you should expect the air conditioner's run time to be reduced compared with that on days when the difference is more significant. That said, a concern with short cycling is the potential for high indoor relative humidity when there is little or no air conditioning called for and little dehumidification as a consequence.

  • 3 years ago

    Some thermostats have a cycle per hour setting. See if yours has this feature and the setting value. You can try setting it to 3 ot 4 cycles per hour to help reduce the cycle times..

    HU-597194232 thanked mike_home
  • 3 years ago
    last modified: 3 years ago

    Older thermostats used to have a degree setting, as in - turn on the equipment when room temperature varies from the setting by .25, .5, .75, 1.0 degrees, etc.

    Many newer thermostats have adjustable cycles per hour setting instead. I have some that are adjustable (lowest setting =2), and one at another location that is preset to 3 cycles. per hour. Remember that 3 cycles per hour can mean 10 minutes on, 10 minutes off, so that's not exactly longer cycling.

    Shorter cycling is harder on the equipment, so many starts and stops. Heat exchanger doesn't fully heat up in heating mode, coil doesn't fully cool and remove moisture in cooling mode. I believe equipment is happier and lasts longer with longer run times. When I'm hanging around and find my temp setting is causing frequent ons and offs, I'll change the setting to a few degrees off the desired temp (Lower for cooling, a bit warmer for heating), let it reach that setting, and then return it to the preferred setting and let it coast back to that point.

  • 3 years ago

    Post your Thermostat model. Sounds like an anticipation/CPH setting.

  • 3 years ago

    Sure. Its a Honeywell t10 prosmart with

  • 3 years ago
    last modified: 3 years ago

    You can set the Honeywell T10 Pro maximum cooling cycles-per-hour in Installer Configuration, ISU #3140.

  • 3 years ago

    Good luck trying to interpret that manual's explanation of anticipation ("droop")!!!

  • 3 years ago

    Oh, those aren't so hard. When you enter the installer settings mode, you simply touch "Next" to scroll through the various settings until you get to the one you want.


    On my Honeywells, it's necessary to enter a thermostat-specific passcode to get into the installation/settings area intended for pros. (This I suspect is to keep homeowners from messing with the settings and screwing them up). The passcode is a 4 digit number printed on the back of the thermostat, on the product ID sticker. Locked door now open.

  • 3 years ago

    @sktn77a: "Good luck trying to interpret that manual's explanation of anticipation..."

    I assume that's ISU 3090 'Backup Heat Differential' but one can just leave it at the default, "Comfort".