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  1. #14
    Join Date
    Sep 2002
    Posts
    22,539
    Post Likes
    Let's look at it with some basic logic -

    "Runs 2 hours - then is only off for a few minutes."

    That sounds like tremendous heat-gain: The unit takes 2 hours to lower the house temperature one degree or less - the thermostat's differential - and as soon as the AC shuts off the continually incoming heat almost immediately triggers the AC back on again. Where is all that heat coming from?

    Is the roof black or otherwise dark?
    Is there any tree or other external shading?
    Is there any insulation in the attic?
    If so; how much?
    Was there an attic exhaust fan?
    If so; does it work?
    Are there inlet vents to the attic space?
    In the middle of the afternoon are the interior ceilings warm to the touch?
    In the middle of the afternoon are interior surfaces of the west walls of the house warm to the touch?
    Thermopane windows?
    Good weather sealing?

    And this is all when it's only 85 outside? Let's forget the AC for the moment - what is going on with the building envelope?

    PHM
    -------


    Quote Originally Posted by ajlocke View Post
    1500 sq ft raised ranch built in 2001. Just had a 3 ton rheem ac put in, we just moved in so I don't know what "normal " run time is for this home. Ac runs for about 1 1/2 to 2 hours reaches/maintains set temp shuts off then cycles back on within minutes. Thermostat temp does not go up before it cycles back on. Could it be the thermostat? It is located in the hallway. I have a room thermostat that reads a degree lower than wall tstat when running and quickly goes up a degree when unit cycles off. Outside temp 85,dew point 65 humidity 53%. It's 2 hour run time to long? Tstat set to 76 stays at 76 the whole time it's running,even when it first turns on (room thermometer says 75)
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  2. #15
    Join Date
    Jun 2018
    Posts
    7
    Post Likes
    Thread Starter
    Quote Originally Posted by Poodle Head Mikey View Post
    Let's look at it with some basic logic -

    "Runs 2 hours - then is only off for a few minutes."

    That sounds like tremendous heat-gain: The unit takes 2 hours to lower the house temperature one degree or less - the thermostat's differential - and as soon as the AC shuts off the continually incoming heat almost immediately triggers the AC back on again. Where is all that heat coming from?

    Is the roof black or otherwise dark?
    Is there any tree or other external shading?
    Is there any insulation in the attic?
    If so; how much?
    Was there an attic exhaust fan?
    If so; does it work?
    Are there inlet vents to the attic space?
    In the middle of the afternoon are the interior ceilings warm to the touch?
    In the middle of the afternoon are interior surfaces of the west walls of the house warm to the touch?
    Thermopane windows?
    Good weather sealing?

    And this is all when it's only 85 outside? Let's forget the AC for the moment - what is going on with the building envelope?

    PHM
    -------
    Dark roof,yes. Was told at inspection that there is alot of insulation in attic. No attic exhaust fan as far as I know. Inlet vents yes. I have not noticed walls or ceiling being warm. We have a small tree in the front and one in back neither provide much shade. Doubt these are thermopane windows. We are having someone come out in a few weeks asses the "energy" efficiency of the home.

  3. #16
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    8,464
    Post Likes

    Grinding out the Grid

    WE NOW KNOW the residence location within 44,612,474 Acres.

    37.0'N to 39.5'N

    38.3' +/- 1.3'N … 93.3'F / 75.9'F DB/ WB ASHRAE 1% design point

    NOT Too many Annual Cooling Degree Days (CDD) < 1,700
    HDD < 5,000

    -------
    Energy Audit overview can normally be determined from
    electricity usage for EACH of the last 24 months
    _________________

    Calc is now within ~ 25% accuracy
    ______________

    I know my A/C system does Not run too much.
    It's always < 15 hours / day.
    _________------____
    Attached Images Attached Images   
    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

  4. #17
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    8,464
    Post Likes
    Quote Originally Posted by ajlocke View Post
    Missouri and that was outside rh
    38.5385950638 ' + / -
    Attached Images Attached Images  
    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

  5. #18
    Join Date
    Jun 2018
    Posts
    7
    Post Likes
    Thread Starter
    Quote Originally Posted by dan sw fl View Post
    38.5385950638 ' + / -
    everything you said is foreign to me,update is 93 today with a heat index of 100,ac has not shutoff and staying a degree above tstat temp.

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