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  1. #14
    Join Date
    Sep 2011
    Location
    Orlando, Fl
    Posts
    4
    Post Likes
    Thread Starter

    Manual J

    Gentlemen,

    Thanks for the great feedback and advice. Unless someone has a different perspective I think I have enough information to proceed. My profession is road contracting so I do appreciate the personal sacrifice each of you made in pulling away from your families and business to help me. I am an avid DIY but I learned along time ago if the pro makes it look easy, IT ISN'T!. Fixing my AC problems is one place where I want to hire the best and make sure they do it right. Thanks again.

    Ed

  2. #15
    Join Date
    Dec 2003
    Location
    Citrus County, Florida
    Posts
    2,618
    Post Likes
    I perfer to do my own load calculations as I will not trust anyone else since I will responsible if the sizing is incorrect. Every changeout should have a whole house calc done. The old unit may have been the wrong size to start with and with today's more efficient equip, you may get away with a smaller system. And yes you may have to pay for it.
    Doug

  3. #16
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,976
    Post Likes
    A manual J is not your first step in sizing your new a/c system. The first step is determing what can be done to improve your homes "thermal envelope". This can be done by a BPI or RESNET trained energy auditing company. The odds are very good that your existing system was oversized by as much as 1 or 2 tons, that your ductwork is undersized to accomodate your existing system, and that the only reason you havn't noticed a problem with these facts is because your home is too "leaky" (air infiltration) and your ducts are too leaky.
    It is estimated (by someone with a brain) that only 1 in 10 existing duct systems were installed in a manner that will allow newer higher efficiency systems to operate at even 80% of their rated efficiency levels.
    Forget "industry standard practices" and find a company that is re-writing those practices.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  4. #17
    Join Date
    Sep 2011
    Posts
    6
    Post Likes
    beachtech
    great Neil Young link ...... thanks

  5. #18
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    8,095
    Post Likes

    Smile

    Quote Originally Posted by skibme View Post
    I found using a distance meter in addition to a tape measure helps you do it faster.Tape measure for windows and doors.
    I just keep my stride and eyes calibrated.

    ...
    __ GreAt MeaSUREment TOOLs.
    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. #19
    Join Date
    Sep 2011
    Posts
    9
    Post Likes
    Well sh*t. Now what do I do? Ask the best contractor to do a heat loss evaluation on the site?

  7. #20
    Join Date
    Jul 2006
    Location
    Fl
    Posts
    1,117
    Post Likes
    Quote Originally Posted by tipsrfine View Post
    The odds are very good that your existing system was oversized by as much as 1 or 2 tons, that your ductwork is undersized to accomodate your existing system,
    My shop manager and I were just discussing this yesterday.... we were just kinda saying.... Why?? It was prompted by an estimate I was working on. Big beautiful house, big oversized equipment, way undersized duct.

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