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  1. #1

    Brand new System Short Cycles

    Ok...Heres The Scenario...

    Location South Florida.....Home size 1500 square feet.

    Just replaced a 8 year old contractor installed 2.5 ton Bryant with a new 2.5 ton Ruud. Did a new compressor, air handler and programable White-Rodgers T-stat. As a FYI the compressor is 14.5 SEER and the air handler brings the SEER's up to 16.

    Once the system gets to set temp of 77 degrees it will shut off for 5 minutes....5 minutes later it wil start up again even though the temp still says 77. I have reset the T-stat back to factory default and reloaded settings, but have not noticed a change.


    Any ideas?
    Last edited by smiggleburger; 05-21-2010 at 01:44 PM.

  2. #2
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,368
    There might be a cycles per hour setting in the thermostat that needs to be adjusted. 3 is a good setting, but might need to try 2 if still short cycling. If the old unit didn't short cycle, I don't think it's an issue of the system being oversized (though 2 ton may have been better depending on load calc).

    If you post your thermostat model number, someone here can look it up for you. Or if you have the installation instructions you can find that setting. Probably do not want to reset it to factory settings, however--that may have thrown off some settings.

  3. #3
    Unfortunately the thermostat does not offer the cycles per hour setting. Perhaps I will have to upgrade to a better one?

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,907
    Most stats try to hold a real tight setting so not varying off 77 is probably normal. You keep it warm and if it isn't steaming hot outside, the unit could cycle that fast.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,743
    What brand and model number thermostat do you have.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #6
    Looks like the new t-stat(White Rodgers) is to blame for the short cycles. We swapped in the old one(8 year old Robert Shaw programmable)and everything started to work as normal. Will be getting another one in the next week or so.

    Just as a FYI.... the t-stat that failed is a White Rodgers 70 Series part# 1F78-151

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