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  1. #1
    My house is located in the Arizona desert where summer temps are 110+. The house is a single story, approx 1500sf, with 10 foot ceilings all the way around. The house has a stucco exterior and was constructed in 1997. How large of a unit is needed? Do I really need a 4 or 5 ton unit or am I getting ripped off? Thanks

  2. #2
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    click the bullseye and do a load calculation
    you know the info about you house
    a load cal is the only true way to answer your question

  3. #3
    Join Date
    Feb 2003
    Location
    S.W. PA
    Posts
    3,298
    did the company that is installing do a load calc?
    ask they may have
    if not ask why
    it should have been done if you are getting a new a/c

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,374

    Exclamation YES

    Originally posted by bennydeez

    Arizona desert
    temps are 110+.
    single story, approx 1500sf,
    with 10 foot ceilings all the way around.
    stucco exterior
    constructed in 1997.

    Do I really need a 4 or 5 ton unit or am I getting ripped off?
    VERY VERY Likely
    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. #5
    Join Date
    Mar 2004
    Posts
    1,042
    That sounds like an awful lot for recent construction. The desert is very hot, but there's no humidity. With any size system in that climate, it's imperative that the airflow through the ducts is good- in excess of what is required in any other climate. In most areas 400 cfm per ton is normal; in humid areas, it's more like 350, to help with dehumidification; in the desert, you can't get anywhere near the rated capacity of a system running less thaan 450 cfm/ton.

    Putting in a larger tonnage system to get more cooling capacity is going to kill you with utility bills if the ductwork can't handle even more airflow than it's moving now.

    First, why don't you tell us why you are replacing the current system? If it worked fine but just croaked and needs replacement, there is no reason to get a system larger than the one you were happy with.

  6. #6
    The house was a new purchase for us and this is our first summer. The HVAC company will be back out to do a load test in a few days. The current system has been tested and retested and is working fine but it just cant keep the house cool.

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