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Thread: sizing house

  1. #1
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    Hmm

    looking for some input for sizing the right size outdoor condensor to the size of the house. the home is 2800 sguare foot living space i know theres alot of variables i have to take into account like heat loss etc... but im mainly looking for what tonnage am i looking for. or for some one out there to let me know if theres a caculation i could do to find this imfo out . thanks

  2. #2
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    I suggest manual n. and do load calculations accordingly

  3. #3
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    Click on the bull's eye at the top of this screen.

  4. #4
    Spending $50 on the bullseye may have saved me $2700 in unnecessary expense.

  5. #5
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    SW FL
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    Exclamation Comprehensive Assessment

    Originally posted by cool luke
    home is 2800 sguare foot living space

    i know there's alot of variables i have to take into account like heat loss etc ... but im mainly looking for what tonnage am i looking for. or for some one out there to let me know if theres a caculation i could do to find this info out
    1. Size is ~1/3 of the solution.
    How many units, equipment placement?
    2. Air Distribution: Duct, Diffusers & Return
    3. Installation craftsmanship


    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
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    Originally posted by bama 101
    I suggest manual n. and do load calculations accordingly
    I think you mean manual J, for residencial.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
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    I also recommend the HVAC-Calc program linked here. My new home was rated by the architect at 6-6.5 tons. Other dealers said nothing below 7 tons. The HVAC-Calc program calculation came in at 4-4.5 tons (depending on window coverings).

    I don't believe there is any substitute for a load calculation, but I sure found the majority (almost all) of contractors don't believe in them or just don't want to spend the time to do them.

  8. #8
    Join Date
    Jul 2002
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    962
    Originally posted by cool luke
    looking for some input for sizing the right size outdoor condensor to the size of the house.
    How about the inside coil? Do you already have one ?

  9. #9
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    Thanks for the correction but yes i meant manual j

  10. #10
    Join Date
    Nov 2004
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    SW FL
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    Checking.

    Originally posted by nathan9999
    _ rated by the architect at 6.5 tons.
    ___ Dealers said nothing < 7 tons.
    ___ HVAC-Calc program calc came in at 4.5 tons

    I sure found the majority of contractors don't believe in them or just don't want to spend the time to do them.
    Your final selection was ___ tons for __ square feet.

    Continuous run time is from ___ PM to __ PM
    at ~92'F ( Design ___ F) outside temperature.

    Are you certain that the Manual J led you in the right direction because you very accurately described the building envelope ?

    Did you select your system size at 90% ( or ___ ) of the HVAC-Calc sensible load?

    Nathan, Thanks for the verification.
    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

  11. #11
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    Bakersfield, CA
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    Dan, I don't have the report here but I'll try from memory.

    Your final selection was ___ tons for __ square feet.

    3139 sq ft and 5 tons = 638 sq ft per ton

    Continuous run time is from ___ PM to __ PM
    at ~92'F ( Design ___ F) outside temperature.

    HVAC-Calc design temp was 104. I changed it to 110 (I know that is defeating the purpose, but I'm a chicken)
    Continuous run time - I don't remember that being in the program prompts - perhaps it's built into the program.

    Are you certain that the Manual J led you in the right direction because you very accurately described the building envelope ?

    I hope so. I really took time to enter accurate information.

    Did you select your system size at 90% ( or ___ ) of the HVAC-Calc sensible load?

    The program reported a 4.5 ton unit when using no window coverings (recommended in the program user's manual). I can't remember if the program uses a % when comning up with the recommended tonnage.

    I decided on 5 ton as we will be zoning with 3 zones and using a VS furnace. I'm hoping VS and the Trane zoning system will offer me the benefits I'm looking for. I was too chicken to go with the 4 ton.

    Trenching on July 25, so nothings is set in stone on HVAC.

    Hope this answers your questions.

  12. #12
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    SW FL
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    Originally posted by nathan9999
    Dan, I don't have the report here but I'll try from memory. Your final selection was ___ tons for __ square feet.

    3139 sq ft and 5 tons = 638 sq ft per ton

    Continuous run time - I don't remember that being in the program prompts - perhaps it's built into the program.

    I decided on 5 ton as we will be zoning with 3 zones and using a VS furnace. I'm hoping VS and the Trane zoning system will offer me the benefits I'm looking for. I was too chicken to go with the 4 ton.

    Trenching on July 25, so nothings is set in stone on HVAC.
    "Continuous run time" can be determined AFTER you are in your house.

    5-tons is likely a MINIMUM acceptable unit.

    Hope that you can set 84+ 'F in one ( East) area
    while you cool the other two zones (south or west facing) to normal set point.
    Otherwise, I don't see significant benefit in zoning a 5-ton.
    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

  13. #13
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
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    209
    dan, I don't mean to highjack this thread, but you are the first person who has responded to me on this site who (seems) to question the value of the Manual J calculation. If the Manual J shows 4.5 tons with no window coverings and closer to 4 with actual window coverings, combined with the fact that I added 6 degrees to the design temp, then why would a 5 ton be the minimum acceptable unit? Just curious.

    Your statement about setting an east zone to 84 leads me to believe that you think a 5 ton unit will be undersized.

    As to the zoning question, the house is a split wing with 3 distinct living areas. Zoning seems to offer a good way to meet the varying comfort demands of each zone and yet use only one unit. My experience on this site, and with the local contractors, is that most aren't crazy about zoning (although locally the ones who are against it have never done it).

    My selected contractor does have experience zoning and it seems like a good option for me. My other option is to use 2 units.

    I appreciate any additional insight you may be able to provide me as I make this final decision.

    Thanks again.


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