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  1. #1

    How to size an HVAC unit?

    While waiting for a dream job, I'm doing service work on my own and I notice homes that are only 5 years old have undersized units? Can anyone tell me what size an HVAC unit should be or how to size a unit for homes? I had a service call for a condensing unit not running and I noticed it was an obviously undersized unit for the home. It was a 3100sf home with a 3 ton or 3 1/2 ton condensing unit. Could anyone tell me what size unit that home should have? I'm thinking it should at least have twice what it currently have. The customer said it takes a long time to cool the entire house.

  2. #2
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  3. #3
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    Jan 2004
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    Guess that means you think a 4000 sq ft home should have more then 2 tons of A/C.

    Sq ft alone. Does not indicate what size A/C a house needs.
    Use the posted link. And you will be able to learn how to size.

    Next. An under sized duct system. Will make a properly, and an over sized A/C take long to cool the house. A/C is not suppose to be a quick process. Since in most areas. Dehumidification is an important part of the cooling process.
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  4. #4
    Join Date
    May 2009
    Location
    Jonesboro, AR
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    111
    And you're a service tech?

  5. #5
    Join Date
    Nov 2005
    Location
    Charlotte, N.C.
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    961
    Quote Originally Posted by mdevera211 View Post
    While waiting for a dream job, I'm doing service work on my own and I notice homes that are only 5 years old have undersized units? Can anyone tell me what size an HVAC unit should be or how to size a unit for homes? I had a service call for a condensing unit not running and I noticed it was an obviously undersized unit for the home. It was a 3100sf home with a 3 ton or 3 1/2 ton condensing unit. Could anyone tell me what size unit that home should have? I'm thinking it should at least have twice what it currently have. The customer said it takes a long time to cool the entire house.


    Was it a 3 ton or 3 1/2 ton? Since you obviously don't know how to size equipment how are you determining it's undersized?
    Those who restrain desire do so because theirs is weak enough to be restrained. (William Blake)

  6. #6
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    Mar 2005
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    Hey BT, why not tell this guy about applying for professional status.
    He's got the post count. Seems like he's trying to learn something.

  7. #7
    Join Date
    Jan 2004
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    Lancaster PA
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    Quote Originally Posted by the dangling wrangler View Post
    Hey BT, why not tell this guy about applying for professional status.
    He's got the post count. Seems like he's trying to learn something.
    What. You couldn't copy and paste from one of my post with it in.



    OP:

    You have the post count, apply for Pro Membership.
    Use this link and Apply for Pro Membership

    Once accepted, you have access to the pro tech forums. Where you can ask and get answers to technical questions.

    Plus, you also have access to the Pro Educational Forums.

    All of it is free.
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  8. #8
    Join Date
    Mar 2005
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    Houston, Texas
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    Quote Originally Posted by beenthere View Post
    What. You couldn't copy and paste from one of my post with it in.



    OP:

    You have the post count, apply for Pro Membership.
    Use this link and Apply for Pro Membership

    Once accepted, you have access to the pro tech forums. Where you can ask and get answers to technical questions.

    Plus, you also have access to the Pro Educational Forums.

    All of it is free.


    That's the ticket!
    I'll bet you agree. No need to give the guy a hard time. Let's try and help him.

  9. #9
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    Jan 2004
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    Lancaster PA
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    We all jump the gun once in a while.

    Stress relief.
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  10. #10
    Join Date
    Mar 2005
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    Houston, Texas
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    Quote Originally Posted by beenthere View Post
    We all jump the gun once in a while.

    Stress relief.
    Honestly, I've never seen you be mean to anybody. And, there's some you should have.

  11. #11
    Join Date
    Jan 2004
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    Lancaster PA
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    I slip once in a while.

    Try not to though.
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  12. #12
    Join Date
    Nov 2008
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    S.C.
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    931
    It's tough being nice in a mean world. You have done a good job today.

    I'm sure they wouldn't let just anyone be a Moderator.
    It's refreshing to pull your head out of the box when servicing a system.

  13. #13
    Join Date
    Mar 2005
    Location
    Houston, Texas
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    Quote Originally Posted by absoair View Post

    I'm sure they wouldn't let just anyone be a Moderator.
    They will for money!

    http://hvac-talk.com/vbb/showthread.php?t=399892

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