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  1. #1
    A/C runs for 1.5 hours to keep house at 76 degees,then shuts off for about 45 min. before coming back on. Is this normal? Air out of vents is blowing at 52 degrees.New 10 seer unit 2.5 tons. 1375 sq.ft.brick home,new windows. Temp outside is 95 degrees

  2. #2
    Join Date
    Jun 2006
    Location
    Michigan
    Posts
    963
    If it's hot out then it's normal. Properly sized a/c can run nonstop for a long time when outdoor temp is near it's maximum design temperature. (95 degrees where I'm from) If you don't stay on long enough you won't remove enough moisture and house will feel damp and uncomfortable. If unit is running non stop and not maintaining the temperature, then you might have a problem.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,599
    Sounds like stat with wide temp swing but anything that cycles off that much in hot weather is plenty sized (oversized probably) and working fine.

  4. #4
    Join Date
    Sep 2004
    Posts
    523
    Wow you must have some really good insulation for your unit to stay off for 45 minutes when it is 95 outside.Unit needs to run long enough to remove moisture from house.If humidity is high outside you should see a good stream of water coming out of condensate line while unit is running.That is if your unit is up to par.

  5. #5
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428

    Question Location ?

    Originally posted by jawslock70
    A/C runs for 1.5 hours to keep house at 76 degees,then shuts off for about 45 min. before coming back on. Is this normal? Air out of vents is blowing at 52 degrees.New 10 seer unit 2.5 tons. 1375 sq.ft.brick home,new windows. Temp outside is 95 degrees
    Do you live close to the desert?
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  6. #6
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,121
    Originally posted by fixerup
    Wow you must have some really good insulation for your unit to stay off for 45 minutes when it is 95 outside.
    Yes sir re mine might stay off 15 minutes tops in Houston at that OD temp.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  7. #7

    location for run time

    Home is in northern oklahoma. Unit is in sun 8 hours of the day. Lows at night around 76 degrees. Todays highs around 98.




  8. #8
    Join Date
    Dec 2005
    Location
    Memphis, TN.
    Posts
    824
    I'm in SW MO and that would be god for mee too!

    I'm with Loonie, sounds like your fine.


    Citywide.
    "I don't care what you could get it off the net for, they wont warranty it and neither will I"!

    And if you don't like my "flat rate up front pricing" try and negotiate the price on that big mac you just bought pricing is exactly the same method!

  9. #9
    Join Date
    May 2006
    Posts
    312

    Re: location for run time

    jawslock70 wrote:
    >northern oklahoma. Lows ..76 ..highs 98.

    time to move to florida, highs 88, lows 77. my unit runs about 4 hours non-stop, pauses for 20 min, resumes. keeps house at 77F but am running deliberately with only 1.5 ton compressor for max humidity removal. if temps spike (not yet this summer) above 95F, second compressor (4.0 ton) takes control

  10. #10
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304

    Long runtimes actually desirable

    In my house in S.Texas, have always managed to maintain near the thermostat setpoint. But have observed a run of 3-4 hours on occasion in doing that.

    What I understand from Manual J, is that a regular AC (not 2-stage) is *intended* to run non-stop for a long period during the hottest days. Nobody I know has ever defined what a "long period" exactly is, but when we give examples in the 2-4 hour range, the professionals indicate it is OK as long as temperature is maintained where we need. The goal is to gain efficiency and maximize humidity removal, by using those long runtimes.

    Regards -- Pstu

  11. #11
    Join Date
    Mar 2005
    Location
    Louisiana
    Posts
    211
    Here in Louisiana where I live my unit runs for about 30-60 minutes and shuts down only for about 15 minutes .
    Is the filthy clean?, also when was the blower wheel, evap. coils and outside unit cleaned?
    Two years ago I noticed that it was taking long for my unit to satisfied my stat, I check and the blower wheel was filthy, I cleaned it and also the evap coil, made a big difference in the performance, get a tech to check this out and also check your charge if the unit is an older model and hasn't been seen about in the last 2-3 years.

  12. #12

    run time

    So the system runs longer because outside system is new, and inside is old? Coil is 3 ton. What will this do to my electric bill?

  13. #13
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428

    Run time is Low !

    Originally posted by jawslock70
    So the system runs longer because outside system is new, and inside is old? Coil is 3 ton. What will this do to my electric bill?
    Who knows what the two A/c system efficiencies have been/are?

    lockjaw,
    You can _ N O T _ be serious about electric co$t inquiry when so called "half-new" systme is ~10 SEER condenser and whatever {?? old} coil.

    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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