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Thread: sizing house

  1. #14
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by nathan9999
    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.



    First part is my question as well,I'd say 5 ton is oversized.But I think it's a two speed so not a lot to worry about.

  2. #15
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,001

    Question Regional Comparisons

    Originally posted by nathan9999 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.

    My selected contractor does have experience zoning and it seems like a good option for me. My other option is to use 2 units.
    Zoning is a GREAT Option when the contractor HAS Experience and you have THREE DISTINCT areas.

    I perform Manaul J 8th edition calcs EVERYDAY for
    the local area and the calcs rarely indicate
    > 600 Square Feet per Ton
    for 18'F differential outside/inside temperature.

    Whereas you have selected a 35'F differential Temp.

    Standard Design temperatures here are
    93'F /78' DB/WB and 75'F /50% RH.

    I guess the glass areas are significantly higher
    (~20% of floor area)
    in SW FL than other sections of the country.

    I doubt that the 10-foot ceilings
    found here are That Unique.

    How large is the BY-PASS
    (equivalent to the air flow of the 2 larger zones,
    i.e. 1400 CFM or so)?

    I am just trying to discover and loosely define regional differences for myself.

    [Edited by dan sw fl on 07-16-2005 at 09:10 PM]
    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

  3. #16
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Dan,

    bypass size for 1400 cfm,sized how FR,fpm,etc.??

  4. #17
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,001

    ???

    Originally posted by dash
    Dan,

    bypass size for 1400 cfm,sized how FR, fpm, etc.??
    Right,
    _ HOW is a ?
    _ 1,400 IS a ?
    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
    Jan 2005
    Location
    Bakersfield, CA
    Posts
    209
    Dan,

    I perform Manaul J 8th edition calcs EVERYDAY for
    the local area and the calcs rarely indicate
    > 600 Square Feet per Ton
    for 18'F differential outside/inside temperature.
    Whereas you have selected a 35'F differential Temp.

    I know you are in a humid climate, whereas we are in a relatively dry climate-average rainfall 6 inches per year, basically desert like. I don't know if that would account for some of the differences. The HVAC-Calc program listed 55 grains of moisture for summer.

    Standard Design temperatures here are
    93'F /78' DB/WB and 75'F /50% RH.

    For the inputs into the program I listed:
    O/S design conditions as 110/32 (summer/winter), inside as 72/72 50% RH

    I guess the glass areas are significantly higher
    (~20% of floor area) in SW FL than other sections of the country.

    The windows and glass doors inmy house represents 17% of the floor area.

    I doubt that the 10-foot ceilings found here are That Unique.

    We have 10 foot ceilings as well

    How large is the BY-PASS
    (equivalent to the air flow of the 2 larger zones,
    i.e. 1400 CFM or so)?

    I have no idea. I'd have to get that from contractor.

    I do know that the Trane integrated zoning system is supposed to regulate air flow. I don't know if that has anything to do with a by-pass.

    I hope this answers your questions. As I've mentioned before, I'm an accountant, not an HVAC professional. I have made my choices based on information gained from this forum, my local dealer and the distributor.

    Thanks again.

  6. #19
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836

    Re: ???

    Originally posted by dan sw fl
    Originally posted by dash
    Dan,

    bypass size for 1400 cfm,sized how FR, fpm, etc.??
    Right,
    _ HOW is a ?
    _ 1,400 IS a ?

    Is that a question?If so I'm not sure what the question is?

  7. #20
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,001

    5-Ton ...38'F Delta T

    Originally posted by nathan9999
    Dan, I perform Manual J 8th edition calcs EVERYDAY for
    the local area and the calcs rarely indicate
    > 600 Square Feet per Ton for 18'F differential outside/inside temperature.
    Whereas, you have selected a ~ 35'F differential Temp.

    For the inputs into the program I listed:
    O/S design conditions as 110/32 (summer/winter),
    .... inside as 72/72 50% RH

    The windows and glass doors in my house represents 17% of the floor area.

    We have 10 foot ceilings as well

    How large is the BY-PASS
    (equivalent to the air flow of the 2 larger zones,
    i.e. 1400 CFM or so)?
    I have no idea. I'd have to get that from contractor.

    As I've mentioned before, I'm an accountant, not an HVAC professional.
    I didn't realize you are " in { close to} the desert"
    Differential Temperature = 38'F

    Very Nice Equipment selections!
    ..Zoning with 2 speed ( or 2-stage TRANE XL16I ) condensing unit and Variable Speed air handler.

    CONFIRMING your selection of 5-TON as appropriate with
    my "Cooling Capacity Quick Estimator" calc.
    ________________ BTUh__
    Glass _______ 25,154 __ S.H.G.C. 0.46
    _________________ + based on assumed orientation
    ________________ .. ANDERSON " Grey" tint
    ..... _R-value
    Ceiling _ R-30_ 5,413
    Walls _ R-19_ 6,160
    Floor (Review, IF Raised)
    Duct _ R-6 _ 7,350 for 130'F attic

    Infiltration
    A.C.H. 0.20 _ 2,053
    Internal Gain
    ( kW ) 0.42 _ 2,433
    People 6.00 _ 1,800
    _______ 40,389 BTUh Sensible Load
    _______ .. 54,579 BTUh Total Capacity
    _______________required with S.H.R. 0.74


    [Edited by dan sw fl on 07-18-2005 at 12:16 PM]
    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

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